The WRONG way to make an AC-powered clock đ
VloĆŸit
- Äas pĆidĂĄn 29. 06. 2024
- Connecting a 1.5-volt AA battery-powered quartz clock mechanism directly to 120 volt AC mains power seems like a bad idea. But this Chicago Lighthouse clock somehow makes it work, in a very wrong way.
Time flow:
0:00 Introduction
1:16 Unboxing
2:51 Quartz mechanism
5:06 First test
6:37 Opening the cover
8:19 Circuit analysis
13:15 Conclusion
#clock #electronic #teardown - VÄda a technologie
*Correction:* As several viewers pointed out, only one of the diodes is functioning as a rectifier. The other three serve as voltage regulation.
A very large valued resistor is what is being used to create the voltage drop difference across the clock mech.
Couldn't see the quartz crystal in the AC clock.
Can it not be a capacitor dropper?
@@lealcy It's inside the plastic housing.
Yeah, makes sense. That feeling when you see four diodes in a power circuit and you instantly assume it's a FULL BRIDGE RECTIFIER, because you see them all over the place and that's how things are done...
Train station clocks, especially the ones in Europe (You showed one in Switzerland) actually work different from most clock mechanisms. The second hand usually sweeps in 58 seconds around the clock to the 59 second marker, stops 1-2 seconds, and waits for a central sync pulse to jump to the 00 and spin again. This is done since more than 120 years to centrally keep all clocks along a trainline in sync with a simple single sync pulse, and very low precision at the individual clock level.
OMG I've always wondered why they pause at the end of the minute and couldn't figure out what to google. Thank you so much for this!
those trainstation clocks are not really clocks at all... they're just slaves to a master clock... the slave movements just follow the sync pulse... nothing else...
It's even cooler when you think about how they adjust for summer time! When the time moves ahead an hour, overnight the frequency of the pulses increases temporarily to allow the clock to get ahead. When summer time ends, the pulses simply stop for an hour.
@@thiesenfand theyâre synced with DCF77
So it was not just me who saw the pause
"Which would spill the gears out..." *proceeds to spill the gears out himself*
Hey hey! The Chicago lighthouse! Good chances that whoever made that clock was either blind or visually impaired, they're an organization in the west side of Chicago (1800 Roosevelt or so) who helps employ people with vision difficulties. My dad used to work there in his 20's way back in the 90's, a few big jobs they hired for was working with light sensitive photographic film and printer toner cartridges.
The clock movement says made in PRC.
â@@westelaudio943But entire clock "assembled in the US"
I am very happy that you, sir, brought that up. I was getting ready to roast his nuts over not mentioning that visually impaired people most likely assembled this clock(and not the PRC).
@@johndododoe1411
Yeah but that's just the clock face.
So that's no excuse. They probably ordered the cheapest movement from Winnie Pooh land, no idea why you would do that for something that gives me the impression of a high quality product otherwise.
@@westelaudio943 This is typical fake quality junk from someone completely devoid of having a quality mindset .
If you pay close attention to the board layout, only one diode is used for rectification. The other three represent a makeshift zener for voltage regulation. So, the resistor actually experiences a voltage drop of approx. 58Vrms and dissipates about 0.17W. This is still out of spec for 0805 size, but considering the area of surrounding copper traces, it should be fine. Very cheap and pretty clever solution.
well spotted! I calculated about 60v drop for that power (0.4w) and resistor, and was wondering if diodes did the rest...
that also explains delay on startup...that cap is charged by one diode
The resistor is dropping from 108 to 2 volt but only on one cycle (when the rectifying diode is in conduction mode) that means dissipated power is V^2 / R /2 = ~0.35 W as written on the mechanism casing - anyway way too much for that small SMD - overtime it would get quite hot and possible damage the pcb of the plastic casing
Cheapest and not as clever as capacitor with full bridge rectifier.
@@Freeman666Gordon Actually with a full bridge rectifier, the tension on the Capacitor would be less predictable as it would depends on the charge/discharge current and time. By using the three diodes as a voltage regulator, tension on the capacitor cannot be higher than ~2.1V otherwise the diodes are in full conduction mode and would drain all the current passing through the resistor.
@@Freeman666Gordon
What's a "FULL BRIDGE" rectifier?
I've seen (and used) *MANY* "f u l l - w a v e" rectifiers in my career - some were of the "bridge" type configuration, but many of the FULL WAVE rectifiers I've seen (AND USED) are not BRIDGE rectifiers, BECAUSE THERE WAS A CENTER TAP ON THE TRANSFORMER!
Before the quartz revolution, I had a mechanical clock which did not require any manual winding up, because it included a small battery powered motor which cut in about every 10 minutes to wind up a small clock spring automatically.
I thought that was a clever design.
By the way, that 20K resistor is dissipating 0.7 watts.
the power handling is actually half of that, 0.35 W; only one diode is used to rectify the AC and charge the capacitor, which means the resistor is dissipating power only for half cycle.
we used to have one similar
@@enricoself2256 I did my best to trace the circuit, and I think you're right.
I can't actually see the polarity markings of the diodes, but my guess is that AC-Hot connects directly to DC+, AC-Neutral goes through R1, then through D1, into DC- (or, I guess, if you wanted that in conventional current flow order, DC- into D1 into R1 into AC-Neutral.)
D2, D3, and D4 don't actually form part of a bridge rectifier. They _look_ like they're in series between DC+ and DC-, probably as a shunt for ~2V. (0.6 to 0.7V x 3), which is why the DC voltage is consistent despite the intermittent load of the clock mechanism. R1 keeps the current limited. It's a crude voltage regulator circuit.
@@nickwallette6201 yes, that is how that circuit looks like, basically the resistor and the four diodes are all in series and the capacitor is across the last three diodes to keep ~2V to power up the IC and the clock. The three diodes in parallel to the capacitor are barely conducting and a zener would have used too much current (5 mA just to keet the 2.2V reference) so after all is rather a clever design.
It the '70s my parents had a self winding clock powered by a single D cell. There was a spring mechanism to actual run the clock mechanism. Over the course of about 2 minutes an arm, with carrying the + side of the battery, attached to the spring mech would draw closer to a contact for a solenoid. When it made contact the solenoid it would fire off and whack the spring mech back to fully loaded and the cycle would repeat. It was quite loud when it fired but would run for a long time on that single D cell.
I always thought the smooth AC clock hand movement was really cool. Never knew what actually made those clocks work differently from everything else.
I have a DC clock (2 AAA battery) that runs like an AC clock. I don't have a clue how it works.
I had one like that, they drove the mechanism at 16Hz instead of 1Hz, and used a reduction gear for the second hand
@@liam3284 Did it drain batteries faster? or about the same?
That was common for all AC powered clocks, because they ran on a simple synchronous motor.
@@8546Ken Yes. An induction motor that would sync to the frequency of the AC line and with appropriately sized gears, would keep good time as long as the power was stable. In the case of North America, 60Hz. If you were to take the same clock over to the UK and adapt the input for 240VAC, the motor would run slower since it will sync to 50Hz and not keep time since the final drive gearing determined the movement based on the intended region.
I mean, that wouldn't be a bad design if they beefed it up a bit. maybe they could make a mechinism that keeps an internal NiMh battery charged so if the power goes out it still works.
Honestly at that point you might as well just make a design of this clock that takes a D cell battery and you wouldn't have to worry about it for years
@@josh9673 all they would have to do is expose a battery slot and maybe rectify it down to 1.5 instead of 2.3
â@@josh9673the only thing to worry is if the battery electrode starts to corrode and rusting everything around it
Or, just put an alkaline cell in it, remove the cord, and call it a day.
Alternately, just buy the AA-Cell UPS for a battery-powered clock that already exists.
I've seen those before at my work. At the time I never gave it much thought, but as I watched the video, I was expecting to see a capacitive dropper (maybe I've just seen too many Big Clive tear-downs.) But regarding the hot and neutral switched, I'd just about bet that it's random which wires get installed on to which spot, or even if it gets a polarized or non-polarized cord.
As i understand the power companies and generating facilities even are adapted for clocks like this. The 50/60 Hz frequency is that exact and if it is not they can even compensate by adjusting a few ticks with the generators back and forth so that the number of cycles per day is 100 % the same making the clocks stay on time.
@@johnpekkala6941 It won't matter for this clock, as it's not using the AC line frequency as a timing reference. You're thinking of the "normal" style of electric clock, powered by a synchronous AC motor.
â@@Zeem4 There are also digital clocks using the line frequency. Are the ones with AC motor still made? I remember a big ceramic one in my granddads factory. It was loud but ran for many decades.
@@-Tris-not that I can find anyway. It would make no sense cost wise as an ac synchronous motor and gear train are far more expensive than the alternatives that work just as well. I could only imagine it being made for historic or nostalgia purposes
@@johnpekkala6941 Yes, but they donât keep that accuracy for clocks but primarily to keep all the power stations in sync. Even small deviations (like 0.1 Hz) are a sign of trouble within the network.
@4:06 - The tick or sweep second hand... I recently went looking for a basic clock mechanism like this to repair an older clock. I was astounded by the variety and types of these units available. Tick, no second hand, silent sweep, silent click seconds, shaft depth, shaft length, hand size and specifications and so on. It was daunting.
But did you get the right unit for your older clock?
@@cassandrajoiner9933 I ordered a battery-operated, smooth-sweep with the dimensions for the hands that I transferred from the old hands. $9.97 USD delivered - hands included. Edit - I also measured total shaft length, depth and diameter.
"its cock o clock"
@@Mizai You worked that hard, didn't ya. đ
I just swapped hands from my old clock on new 2$ mech. It's pretty loud so i would recommend to go with continuous ones.
Hey now, that sketchy design has UL approval! If anything in that circuit dead shorts though, it'll convert that resister into a fuse pretty quickly.
If you miss the continuous sweep of a vintage AC powered clock, you can still get continuous sweep clock motors in both AC and DC varieties from Seiko. Thatâs what I did. Klockit is my go-to site.
Clocks in institutions are often using a four wire connection scheme where two wires are for power and the other two are a serial bus that transmits time information. Some systems have a two wire arrangement and others use Cat5 ethernet and PoE for that. MobaTime can be credited as one of the large manufacturers of timekeeping and time distribution system and self-setting clocks.
I remember back when they ran off of synchro motors, master set in the office.
You can use Cat5 ethernet cable for any suitable signals.
@@jnharton well, arcnet could use a radiator pipe.
I have some thoughts.
1) The resistor "is on the hot side." In an AC circuit, even with a polarized plug, it isn't safe to assume either side is hot or neutral. You isolate the AC from its earth reference (via galvanic isolation, aka, a transformer) -- end of story. *Or,* you insulate the entire assembly so that neither leg is exposed. You could argue that the plastic cover is doing exactly that. Whether that argument is sufficient, I don't know. Ask UL. But, other than that, it doesn't much make a difference which leg the resistor is on. (Although, it wouldn't have hurt to put a 10K resistor on each leg.)
2) The peak voltage into that 20K resistor is ~160V, which equates to around 8mA. If the circuit were a dead short, that would be 1.3W. That resistor is definitely not rated for 1.3W, but it's not under a 100% duty cycle either. On the AC side, if it were into a direct short, it would be more like 0.6W average, which is still too high, but the circuit isn't a direct short except when the capacitor is empty.
EDIT: Not quite. D1 is the only rectifier diode. It's not a FWBR, it's only half-cycle. D2, D3, and D4, together with R1, look to form a shunt regulator.
All in all, this was engineered right up to the line, but it does in fact seem sufficient to me. As they say, "anyone can build a bridge that stands, but it takes an engineer to build a bridge that _barely_ stands."
Seeing as it has an RU mark UL must think it's pretty decent. I think people have sort of been trained to avoid crude non isolated power supplies like this, but it's perfect for replacing a AA that lasts months/years in a plastic clock.
How is it a good replacement if the battery lasts for a year or longer and now you need to run a black cord along the wall that someone could pull? And you don't have a backup battery in case the power is lost.
@@Broken_Yugo I don't think those marks can be genuine. Surely you can't get those marks for something that doesn't have proper strain relief on the incoming mains cable and can be fairly easily opened without using any kind of tool.
They probably didn't pay any attention to how the line cord was wired. They may not even be consistent.
@@j7ndominica051 How is it a good replacement? It depends on what you find more convenient: Not having to have an outlet nearby, or not having to ever change batteries. This is why both options are available. There isn't a "best" solution. There's a right solution for a given need.
The power consumption is so low that the resistor is doing its job, but I imagine a great spectacle if that resistor fails shorted.
đźA great Spectacle!ÂĄ!ÂĄ There Are Those Whom Would Call
It Other Other Things... âŒïžđ„đđđ”đđ«đ©đđ€đ
It would blow or trip the breaker
It will never fail short. If it does it will be for a nanosecond. No drama.
â@@martinda7446Why do you think that?
@@andrewsawesome it'll blow soon after that nanosecond
That is fascinating. They went all that way and didn't include any energy storage device. A low cost capacitor (or supercapacitor) could be placed in the circuit so that the clock could have hours of ride-through for power losses. That would be so simple. Thanks for showing it to us! Hope you do a modding video where you correct the L and N reversal, as well as the lack of overcurrent protection and possibly add an energy storage device.
one of the main reasons you'd find those plug for clocks in the kitchen, is that they would be on the same circuit as the fridge so if you lost power you'd know how long the power was out and to know if the food was spoiled
Maybe in some kitchens, but in mine, the refrigerator and stove (a gas stove) are on their own circuit, and everything else in the kitchen is on another circuit, including the clock outlet. But if the power for the entire house went out, then your idea would be useful.
5:48 I totally saw it attempt (and fail) to move again after it was unplugged. The second hand twitched a bit. There was definitely some energy stored up in there somewhere, but not much, and not enough.
I still have somewhere around here an electric wall clock that resets itself for standard time/daylight savings time based off an internal calendar. I bought it a year or two before congress changed the DST start and end dates in 2005... so that essentially ruined the self setting feature of that clock. I probably could've contacted the company about it, but didn't. It used a quartz movement, no sweep second hand. If I recall correctly, it was made by Chaney. I replaced it with a battery operated Sharp atomic clock (sets itself off WWVB), which is still working fine today.
We have (EDIT: had) a few Emerson SmartSet alarm clocks that set themselves automatically to the OLD DST schedule. We used to change the Time Zone setting temporarily to compensate until the revised versions hit the market. The old ones were downgraded to "need a radio over here for a few minutes" work for a while, until Bluetooth speakers started sounding decent and we sent them off to Goodwill.
What a weird clock... I don't see the point of it. it's a quartz movement, but with the disadgantage of needing to be plugged in.
The continuous second hand of true AC clocks referenced to the 60hz line frequency is what makes them unique, although they drift quite a bit.
Pro tip, of you are going to dissemble a clock. Before you start. Let the second hand go to the 12 o'clock position, before removing the power. Then set the time to the 12 oâclock position. Make sure you mark the position of the motor, where it is, on the rear of the clock. That way when you reassemble the clock, you will know where everything was, before you took it apart. (This doesnât make the clock assembled perfect, for that, you would need to observe the clock, and note the movement, with the positions, at various times throughout the day. Then assemble it to where it would be appropriate.)
Possibly of interest: the Chicago Lighthouse is a century old organization providing services for the blind and visually impaired. They've had a clock assembly factory for decades to provide employment to that population, and they have (or at least had from 1977 to the 21st century) a contract to provide wall clocks for the federal government.
I'm guessing that the current clocks are the result of needing to provide clocks to that government spec (which probably calls for AC wall clocks) in the face of changing tech and needing to use commodity parts vs. having the resources to source a bespoke design.
en.m.wikipedia.org/wiki/Chicago_Lighthouse
I guess the idea is that certain institutions or businesses want to or are required to only use a plug-in clock, the old kind are rare, so the company(ies) that normally make the usual battery powered mechanisms just made a really quick and dirty modified design to meet that demand. The Chicago Lighthouse company just assembles the clock, and this may be they only option or their cheapest option for a plug-in mechanism.
I know almost nothing about electrics/electronics.
And yet I still found this video highly interesting.
Thank you.
âź
That resistor will be fine, as long as you don't try to pull much current, which that clock circuit is doing.
Plus, even if it fails, it will act as a fuse, it's all good.
Thats not a bridge rectifier but rather a single diode as a rectifier and 3 diodes in series to mostly stabilise the voltage to 1.8V. The resistor is dissipating around 300mW then, which is too much for a 0805 sized one. It probabyl will last for a few years, but no, thats not a good or safe design.
could be...i dont think zeners are available as low as 1.5/1.8v ?? not good or safe, because of the tiny resistor, should be a half watt fusible type ,
@@andygozzo72 There are readily available Zener diodes at 1.8 volts and 500 mW. 23 cents each at DigiKey in unit quantities. I don't see any advantage to using one though compared to the 3 forward diode drops as the rectifier diodes are probably cheaper and all can be the same part number so the bill of material is smaller..
We had special connectors for mains powered clocks over here in the UK, again they were generally used in places like schools, we had them in infants school in the 90's.
Actually Iâve created my own version before using a battery eliminator. It converted a 5 volt usb charger into a single AA battery.
That makes more sense than this thing.
What a great damn video man, I'm fatigued of all the other channels like LGR, Techmoan and such but your videos never ever disappoint.
My elementary school had an analog electric clock system, either 70s or 80s design, if I recall they were able to change the AC voltage somehow to set all the clocks in the school centrally. Not sure exactly how it worked, but it was like fast forward, when they did this the minute hand would just fly around rapidly...
I think these ran on pulses sent from the master clock, one every minute. But there was also some way that the clocks jumped forward to correct the time as you mentioned.
I saw that once. Tried to figure out if all the school clocks were wired together.
Some nowadays use PoE and NTP which is pretty cool
This video hurt to watch, because The Chicago Lighthouse is one of those companies that's near and dear to my heart due to the fact that they employ people with disabilities, but especially the blind. I even successfully convinced the company that I currently work at to switch to Chicago Lighthouse clocks, and just last year, they replaced nearly every single clock in the building with various models from the Chicago Lighthouse. The obvious reason they went with this movement is probably cost. There is a manufacturer of clock movements that make their movements right here in the United States (Takane USA, Inc) that they could be using for wall mounted clocks, but as you can imagine, it's quite expensive. A properly built American made 120v AC Takane movement costs $50. As it is, the clock featured in this video costs $70. Even if they only added the break even price of the Takane movement, the total would be $120. So I can understand why they ended up going with this movement.
Interestingly enough, the Chicago Lighthouse isn't the only company that sells American made pluggin wall clocks. There's one other company called the J Thomas Clock Company (which is a subsidiary of Simply Wall Clocks). They also do 120vAC-to-1.5vDC, but in a very different and interesting way. They use a "fake" battery connected to a wall plugin adapter. It's such an interesting way of doing things, that I highly recommend you check it out because I feel that it's video worthy. Anyways, that's just my two cents. End of overly long comment.
I work in a government office that has an old plug-in clock. Looks like it was bought in the 70s or 80s. There's also a battery clock in the breakroom that looks about as old. I've never seen anyone change its batteries since starting here 8 years ago. Both clocks are still running perfectly.
My parents had a small battery powered clock on the wall in our kitchen. They bought it in the early 90s and put it on the wall, and from what they told me, they didn't need to replace the battery until the early 2000s. The battery wasn't even that special; just some generic alkaline. It's shocking how little power a quartz clock needs to keep running.
The official clocks in big organizations are not simple mains clocks . They are slave clocks that are all synchronized to a master clock elsewhere in the institution . There's a somewhat standard protocol for forcing all the clock to show specific time .
that battery shoulde checked regularly for leakage!
@@andygozzo72 oh, it gets taken down every daylight savings time to change the time. I'm sure it's looked at then. For all I know, someone else changed the battery without me seeing? Although, people usually go to me for office supplies and everything in between lol so I'm surprised someone's never looked to me for spare batteries đ
@@andygozzo72 Especially if it is a Duracell.
Before the 120V clock mechanism was opened, I though that a series dropping capacitor would be used in this design. My expectations were clearly too high.
For all the comments about capacitive droppers; it's actually hard to make a capacitive dropper to supply either intermittent loads (like the tick) or so little current. It would need a linear voltage regulator, and that would drive up the complexity/BOM far more than this resistive dropper design.
Years ago (I STILL own this!) My dad bought a gold-plated-plastic "Gilbert" a.c. clock (1959!) This STILL works FINE! This is after "power-surges" etc.! After a "power-out", it would run BACKWARDS until unplugged-and-replugged, BUT IT STILL WORKS! American QUALITY!
1:01 Also, our school uses those AC powered ones. they are not ONLY AC. They are network sync'd. Even if the power were to go out and come back, the clocks can quickly jog forward to catch up to the point (like do 5 seconds in one second or whatever)
I made my own mains powered clock.
Mains comes in and is stepped down via a tiny 240>16v transformer.
The output is rectified and charges a supercapacitor via a 1KR resistor (a reverse diode accross this resistor means that it can discharge as needed, but its charge speed is limited).
Finally, this goes to a 1.5v linear regulator and then the battery terminals.
It's been working flawlessly for about 5 years so far. The supercap works as a reserve for power failures, but only lasts about 15 minutes.
If I remade it, I would instead use a 240>5V transformer. Followed by rectification, smoothing capacitor, and then a LiIon charger module with small pouch cell.
The cell terminals would connect to a 1.5v linear regulator and finally the clock terminals.
You could also use a capacitive divider between transformer and rectifier.
It is not secondhand, but has a second hand.
I used to design some electronic thermostats. I used capacitive droppers if I needed few tens milliamps. But here, for such low consumption, a flame resistant or flameproof resistor is enough.
I worked in a document storage warehouse with battery operated timer switches for each aisle of lights. When I worked there the units were gradually going dead from dead batteries. I wish they had this circuit so they would be more reliable.
I had a more "modern" battery powered clock that made multiple moves per second. It was quieter. It ran down the battery very quickly. A rechargeable cell was the only practical option and even then you had to swap it often. These basic electromechanical clocks work really well. I'd be afraid that the AC clock catches fire or someone pulls on the cord and causes it to break and short out.
Those wall clocks with a synchronous motor were a piece of art. Very rugged, and designed to last a lifetime. The modern model you show in the video is the epitome of cheapness and unreliability; also, it waste 99% of the energy it consumes. In some of my low-power designs I sourced some 120+120 Vac / 3 Vac - 1 VA power transformers, a quarter of a matchbox in size, that could be had for one dollar in bulk. Such miniature transformer can fit into the battery slot, and make this wall clock into a lifelong reliable device. With that SMD resistor, no spacing between the main power PCB tracks, a phenolic PCB with no fuses, and the abysmal power efficiency, this clock is going to fail at the rebound of the first power brownout...
If you plan on using this clock for a long time, I would suggest you change that tiny resistor with a 20k - 1 or 2 watt equivalent dip resistor and adding a fuse to live. The clearance between live and neutral is not sufficient at all...
You could do that...... but the 1/2 watt resistor IS the fuse. It's a 0.4watt circuit. With a 0.5watt fusing resistor.
@@DeadKoby Not every resistor is designed to act like a fuse, in most cases a normal resistor can't act fast enough to protect the circuit properly. Only a fusible resistor can be used instead of a fuse. I do not encourage people to use improper practices just because they work...
@@aktronics yep, i'd strongly advise a half watt proper fusible type, a non fusible one could arc internally under fault conditions, i doubt you'd get a separate fuse of low enough current rating to be of any use,
As DeadKoby said, that SMD resistor IS a fuse. If you replace it with one that _isn't_ a fuse, then I hope you get that fuse sized at least as correctly as the part you replaced for no good reason...
@@andygozzo72 I don't understand where you keep getting the "half watt" idea from? You know ohm's law, you can see the resistor value on the board in the video and he clearly measured the voltage drop across that resistor. Put the numbers inside the formula. 6mA is flowing through this circuit, multiple it by the voltage accros the resistor. This resistor needs to be minimum 0.72 watt. Under normal conditions in a low current circuit the fuse should be rated around 10 times more than the actual current. You can easily find a 250v 50 or 60ma fuse in most electronic stores. As you can see you can find a proper fuse and you can't argue with fundamentals. Simple as that...
Hot and Neutral don't equate like they do in DC. They form a ~170v wave. Neither is a ground. So which side they use as HOT on an isolated circuit is wholly irrelevant.
Almost from the start of the AC power grid, the AC frequency has been regulated by the power stations to keep the long -term accuracy of synchronous clocks accurate to within 15 seconds of true time. For a long time, digital clock radios also used the AC frequency as their time base. So, as long as there is no power interruption, an AC powered clock can run for years and never be more than 15 seconds fast or slow. My clock radio is usually within 5 seconds. In contrast, a quartz-controlled digital or analog clock will eventually drift off. The digital clock in my microwave oven is worse than most, having to be reset at least once a week.
AC control of clocks was valuable not just for home and office clocks, but for all the timer switches used for street lights, and other outdoor lighting.
Synchronized school clocks used a different principle. The ones we had in the early 50's were driven by a wind-up pendulum clock in the principle's office. There was a pulse every second, at 24 volts DC. At 12:00 there was a pulse on a third wire to cause both hands to point to 12. using a separate magnetic actuator and weighted shafts. I know this because I own one of those clocks. The clocks we had in my high school had continuously sweeping second hand, but they could still all be set to the correct time at 12:00. Not sure how they worked. Obviously synchronous AC motors plus a periodic reset mechanism. Probably used 24 VAC
The grade school I attended in the 1940's in Chicago still had wind-up pendulum clocks in every room. In fact, those are known as "school clocks". The janitor had to wind and set all those once a week.
Iâve got an awesome GE AC powered clock. Been in the family since new, was in our vacation home plugged in 24/7 since the late 60âs. When we sold the house I took the clock and now it hangs in my garage. I serviced it when I took it, just cleaned it up and popped in some fresh grease. Itâs a little noisy but hey, itâs never had a break.
I'm very sensitive to the clicking noise of the battery clocks, so I'm disappointed that this clock simply uses the same mechanism. I now live in Ashland, MA, which is the home of the Telechron clock company. It was great to see you had one in the video. The local school mascot is the "Clocker." An elementary school is named after Henry Warren, inventor of the electric clock. We're often referred to as "clock town."
When my clock died i swapped mechanism but did not put seconds arrow. It's quieter that way but not too much
I once had a fever with headache and nausea, and the seconds ticking felt like hitting my head. I took the clock down and put it under a pillow. Now it has a circle in the plastic cover from the seconds hand.
@@j7ndominica051 you can just buy quartz clocks with higher refresh rate lmao
I have fond memories of the loud clicking commercial bomb-shelter clocks we had at my elementary school.
The resistor would blow like a fuse. There probably would be some skid marks on the circuit board.
I wonder if this is one of those weird things that exists for an obscure government/military requirement. Lighthouse for the Blind is a common manufacturer for Military equipment. Is there an NSN number on the box?
It is a known non-profit from California, seems like they do military contracts.
yes, a blind person assembling it would explain why the ac line was wired in reverse
Cool! Can't wait for their AC-powered wristwatch!
I wonder how many people actually want and end up buying a new AC wall clock like this one. Perhaps to replace an older clock thatâs failed that already has its own dedicated AC outlet?
Either way, if I had designs on going the extra mile and installing a plug-in wall clock, Iâd go with an older example; notwithstanding the better quality, Iâve always been partial to the continuous movement of the second hand and lack of any ticking sound that you only get with AC wall clocks.
its like using a nuclear powerplant to power an led night lamp
Not long ago, at least in recent memory, there was another "electric" clock that worked much differently. Periodically (IIRC every 15-20 minutes) it ran an electric motor that wound up a mechanical clock movement. This movement powered the clock display until it ran down, then the electric motor rewound it again. You could detect this mechanism by the periodic "buzzzt" sound it made when winding. Of course, the accuracy was entirely up to the mechanical escapement, not the voltage or line frequency.
They're called self winders. Been meaning to mod a clock I've got to do that (how hard could it be?).
Yes, to my surprise an early incarnation of IBM made them.
I had one of those in my bedroom back in the 1970s. We also had a Kienzle clock that ticked but made a louder clunk every minute as it slightly wound a spring.
The 80's clocks mentioned were cool, after pluging them you needed to "push start" them with a knob in the back to make the seconds hand to start moving.
My paternal grandparents had an electric wall clock in their kitchen, from memory it had a black face and light coloured numbers. Dad told me that earlier on they had another one that apparently was wired up backwards, so the clock would run backwards. Apparently that clock had a white face, and I think Dad said part of it was green. This was clearly before I was born. I think a lot of institutional electric clocks are synchronised such that they keep accurate time, at least they are in radio stations where I've seen them.
When they run backwards, just unplug and re-plug the power cord, and 'likely-as-not' they will run the other way.
It gets interesting when the clock is in a minor-hockey rink (like back in the 60's) and is used to measure a "stop - time" game. (seconds, and even minutes can get added to a game, lol)
@@manifold1476 Perhaps that might've worked, but I think my grandparents got rid of that clock many years before I was born, my family don't even own that house anymore. I always assumed the kitchen clock was hard wired to the mains, it never occurred to me that it might just plug into a power point as we call them here.
Some early electric clocks used synchronous motors that were not self-starting. There was a little shaft sticking out of the back of the clock which you would spin with your fingers to start the motor. This feature was called "spin start". On many clocks you could spin it in either direction and the motor would run in that direction. If you wanted to mess with somebody's head you started the clock backwards... One advantage of this type of clock is that if the power failed the clock would not restart when power was restored and you would be aware that the power had failed. If the clock restarted automatically you might not be aware that it was showing an incorrect time.
My barber has a clock that runs backwards and the face is also a mirror image so when a person is having their hair cut they can look in the mirror in front of them and see the clock and easily tell the correct time.
@@Vincent_Sullivan Yes I've seen backwards clocks with a mirrored face, they were common in the 90s. I had a portable radio with a built in clock once, the radio/tape recorder was powered by 4 D cells and the clock was powered by 1 C cell. The clock, which was analogue, was driven by an electric motor that did not start automatically when you inserted the battery, nor did the clock tick when it was running, so I don't think it used a quartz crystal. you'd set the alarm by turning the time set knob, to set the time you'd push the knob in, to start the clock you'd push and release the knob. you could not force the clock to run anticlockwise, but, you could make the clock run at a high speed by continuously pressing and releasing the time set knob over and over again. When the clock was running you'd hear a faint high pitched whining noise coming from inside it. I don't know what kind of mechanism it used, I'd say the unit was made at some time in the mid 70s. I've no idea of my grandparents' kitchen clock to a spin start motor or not.
I've seen similar line powered clocks from anonymous Chinese sellers on eBay, and my first thought was that they likely used a beefy power resistor and were probably more than a little dangerous. So much for the "beefy" part.
I would have some concern that if the resistor they used were subjected to enough Powerline Nastiness(tm), that it could short, make things go pop and possibly sustain an arc that could be fed by the circuit board turning into carbon. There really ought to be more distance between components or even cutouts in the circuit board. That capacitor probably ought to be rated for across the line use, also to better cope with nasty situations on the power line.
Still, just good enough design is probably...good enough.
I learned to identify bridge rectifiers from ElectroBoom, LOL I catched that up immediately.
I love the 'VWestlife" sound at 6:44, plus we get a new part!
My parents were tired of having to change the battery on their quartz wall clock, so I found a 5V wall wart and used an adjustable buck converter to regulate it down to 1.5V.
I found out awhile back you can actually buy battery operated clocks with a sweep second hand, theyre hard to find but they market them as quiet clocks for use in areas like bedrooms etc where the normal ticking might be annoying, I think quartex or another aftermarket maker might make them as well im not sure. I found this out switching my friends dead motor out for one in another clock she had, I was very surprised to notice the replacement movement had a silent sweep second hand, she was glad to have a silent clock in her bedroom. I didnt bother to notice who made the movement at the time but someone must make it and it should still be available somewhere
This is actually a common practice on small enough electronics. Look up "greatscott Capacitive Dropper". He explains how what this clock is doing can be done with a resistor/capacitor.
This is not a capacitive dropper because the voltage drop is over a resistor and not a capacitor
A capacitor would not waste power as heat and has less chance of failing in short circuit.
@@mevideym but it is still like it.
Complain all you like, but UL says it's safe and it's certified. That's what the RU means, the mechanism is a UL Registered component. File number E351118 looks up to household clock components by Primex Inc.
Note UR/RU just means UL think it's properly designed component that won't burn your house down when used correctly, not necessarily a safe consumer product, ie UL listed. In this case it seems to be plenty fine though.
Doesn't make it a good design. Don't place a lot of trust in the markings anyway, since they're so often faked, but if the unsecured cord is actually approved maybe I should care even less about if the markings are fake.
Interesting, didnât expect to see the standard AA battery mechanism for this. It makes sense though considering they are mass produced and it only needs to be adapted to work on AC input. Looks like it does work, but it could have some improvements. Plus with the voltage being 1.8, seems like a backup battery or a capacitor could be installed that wouldnât need to be swapped out.
_- "... only choice--"_
*Aliexpress:* _"There is another."_
I had one that would click so extremely loud. I could hear it from across the house at night, and when I was in my living room. I could hear it most of the time, if I didnât have my television turned up. After it caught me, I could hear it while watching television. I do have large audio equipment on all of my televisions. Even in my bedroom, and yes, I didnât hear it at first, all the time.
I remember seeing the second hand move smoothly on school clocks and I always thought that was just a design choice and wondered why more clocks donât have it because it looks cooler in my opinion
I recently purchased a quartz wall clock here in Mexico that doesn't tick, it actually has a regular sweeping second hand and is completely silent.
You would have to create a schematic to be sure but that doesn't feel like a bridge rectifier to me. That would have the DC ground rail independent of the AC line and yours is connected to the (hot) AC line as you demonstrated.
well, it would be independent if there was a transformer ie galvanic separation, but they don't have pcb space for such trivialities! heh...
sstc has a comment a bit lower that explains it nicely.
@@ivok9846 which/whether its isolated or not or which pole is live is irrelevant as the 1.8v or whatever is all the clock circuit 'sees' and is local to that, regardless of mains polarity, and yes likely a single half wave rectification, with the 3 other diodes in series as a voltage clamp, i dont think zeners are available that low a voltage,
@@andygozzo72 I don't care about that virtual type of polarity where reversing the wall plug swaps it either.
that part of discussion is irrelevant for me, because nobody will be dismantling that clock while it's plugged in just to kill himself.
also, I would be measuring voltage on the capacitor. but that's probably what he measured at battery terminals anyway.
Many electronic circuits use a dropping resistor for power. Interesting that they used the neutral side for that resistor.
That's... a little terrifying.
I get why they did this - probably nobody actually makes the mechanisms for true AC clocks anymore. Poor implementation though - should have used a capacitive dropper circuit, like the kind Big Clive finds in LED lights all the time.
no need, resistive dropping is ok IF the resistor is a suitable rating đ
@@andygozzo72 True, it probably is OK for this application, but it's really not suitable to drop 110V across a single 0805? resistor. I'd much rather see bigger case size or a couple in series.
@@ccoder4953 i did say 'suitable' rating, that one i would say isnt đ yep, 2 in series much better, even one in series with each mains line...
@@ccoder4953 An 0805 is usually good for 150 V and the power-cord is being used as a heat-sink but I'm still with you that 0805 is a bad idea. With mystery CTI of the PCB and likely mystery flux (driving a pollution degree from hell) the creepage is pretty suspect all over but mostly under those parts. The one thing it has going for it is it's so warm there can be no water for dendrites to short it out!
There used to be some confusion in catalogs where Iâd read about a âsweepâ second hand but then in the showroom/store Iâd be hoping it was the smooth âcontinuousâ movement (microsteps) but it would in fact be the annoying clack clack clack.
I love how the further disassembly didn't result in the gears falling out so you just had to do it anyway.
Up until this video, I have never heard of electric household clocks
Yea i thought battery powered clocks had been the norm for a very long time
I was about to suggest that getting Big Clive to take a deeper dive into this circuit would be useful but the comments section seems to have this well-handled... it answered both of my questions.
Big problem these days with AC digital clocks is Solar PV and battery storage. I have a couple of Bosch ovens and when the PV/battery is powered up they can gain or lose 30 seconds or more per day. With them off they run perfectly.
I used to love the old school clocks that would sync via the HUGE main panel located in the office. Those days are goneđą
And about the Chinese with ac current. Oftentimes they miswire hot and neutral. I have a soldering station for smd and the hot went to the board and the neutral was going through the fuse and switch I had to switch the wires around to make it safe. Just something to look out for.
I love continuously sweeping hand clocks, love that smooth movement.
Jumpy hand is.. meh.
My brother has a plug-in wall clock in his kitchen. In style, it's a backlit bar clock with a glass cover over the dial, though it advertises a tool brand rather than a beer brand. A pull chain turns the light on and off, and metal rod sticking out of the bottom turns the hands to set it.
The second hand moves continuously without ticking, but it's _not_ an AC clock; it runs on 12 V DC coming from a small wall wart adapter, with an appropriately-thin cord for such current. It uses a quartz oscillator for timing, but I imagine it steps the oscillation down to something that still looks continuous to human eyes.
Very interesting! SMD resistors are capable of reliably working on relatively high voltages, the actual voltage raing depends on the size used. For such a low power design this solution is highly inefficient, but dur to tyhe low current the actual power loss is minimal. It would be nuch better with a tiny capacitor dropper citrcuit, like in LED lights, the power consumption would be in miliwatts rang. I see that this mechanism is UL Recognized Component, so it was investigated to be safe according to the standar speciific for such products, however, as it is a "component" and not "end product" so it is possible tyhat there are additional requirements like the need to have a strain relief in the clock itself, or for proper polarity.
Yes recognized only as a component but there is no UL Listed tag on the assembly, very suspicious. A close examination of the mirrored UR symbol shows evidence that it is a probable fake, if so any claims of USA quality is also probably untrue.
@@buddyroeginocchio9105 I've checked UL Product IQ database and the file number shows as valid, however I can't see the model and listed in the database on the clock... Could be a fake one.
@@mibars Good research, thank you. Since earning a UL Listing requires significant professional effort, once it is earned it must be displayed and those who earn it are proud for it. The lack of strain relief amongst other flaws is a strong indicator there has been no agency oversight, that would of course cost money.
I actually replaced all my normal quartz clocks with "silent" versions of the same clock. The hands go smooth like AC clocks but it still runs on 1 AA battery. I can't stand the sound normal quartz clocks make at night. You can also just buy the mechanism to put in your old clock. If you search for silent quartz movement you will find them. I think they are made in South Korea and not China.
It is an unusual design. I like the second hands that move continuously, and have seen battery clocks with them. They usually need one of the sadly-less-common âCâ batteries of my childhood memories.
Fun fact: AAs are just as long as C cells. If the tension is sufficient you can put an AA directly in a C slot, otherwise it will probably work if you wrap it to increase the diameter.
There is one type of electric "clock" still readily available that relies on line frequency: mechanical outlet timers. I think these are still using synchronous AC motors. If you were trying to make your own classic AC clock with modern internals, stealing the motor from one of these would be a good place to start.
The Chicago Lighthouse is an organization that helps people who are legally blind. I dealt with them as an educational professional as a part of the job transition program.
About AC clocks in institutions. They have an advantage besides the janitor not needing to change batteries. You could spring forward an hour, or back by going ahead 11 hours, from some central office. My office building had those until a few years ago, although they became increasingly unreliable at this. It was amusing to watch. I always assumed that they'd vary the frequency of the AC feeding the motor, but I never dissected one.
The clocks use a stepper motor. For hilarious clock hand motion watch an analogue Radio Controlled Clock set itself after installing a new battery.
Still using my small GE school type wall clock from the mid-70's with an electric Telechron movement in my office. Silent and never loses time.
This video needs to be retitled "How to give Big Clive a Brain Aneurysm"
Why? It's actually not that bad. Swapping the neutral and hot doesn't matter when you don't have a ground reference and none of the bits are accessible. About the only 'bad' thing is the clearance between the hot and neutral is probably the bare minimum permissible for 120V supply. The lack of a fuse is probably of concern to some, but the resistor is probably labelled as performing that function.
It's not at all a great design, but there isn't really anything inherently dangerous with it.
It's about time someone brought this up! đ
I came across one of these in a lab at work just last week and I was going to take it apart to find out how they did it. Thanks, no I donât have to!
Great, Vwestlife!
I miss the old clocks with the glow-in-the-dark radium hands.
You would be surprised how many devices use only a resistor or at most a capacitor to drop the ac voltage, I personally don't see any problem with very low power devices, as long as they have some protection in case something goes wrong, like a fuse or a very fine trace.
This feels like something I'd like to see on Big Clive's bench.
I had brought a mini ups over seas and had noticed they have the positive and negative wires which are color coated installed wrong when they had the two pin battery connecter placed on the board.
It works but unless you know electrical and check it in advanced it's going to burn up as the positive and negatives are color coded wrong. I had upgraded it's removable battery to a bigger one found in most ups today as I noticed the one they use might be a poor quality battery found in those ocool storm fans with the same two pin connector to the motherboard.
I notice they that size of wire or bigger on those as seen on tv garage lights but normally the cause of them failing is a bad soldering job as they take a single thread of that wire and solder it to a metal terminal that is about the same size as a ups battery terminal and since the lights are posable the tension slowly works at the threaded wire via the inside where once it breaks they all fail where you can hear that standard pop when you flip the switch where most of anything in the home with audio will make that popping noise.
This is called the âhot zenerâ design and its common in chinese made electronics. I asume both the zener and the resistor gets very hot.
I think they just bought the electronics from alibaba and put it in the clock.
The most common use for this voltatge stepdown is in mobile phone chargers. Never leave your charger plugged in when yourâre not home, because it might fail and cause a fire.
Most the commercial clocks you showed are master clock synchronized and run at 24 VAC supplied by the master clock. One reason clocks running off the mains existed for so long is because the power grid is controlled to be within only a few hz over a 24 hour period giving an easy and accurate enough time reference. Even the master clocks use the mains as the primary frequency for the movement motors in the individual wall clocks for this very reason. Only the master clock itself is running on a verified quartz time keeping circuit that will correct all the slave clocks via a signal that engages mechanical synchronizers in the wall clock movements.
I thought it was a synchronous AC motor clock from the pre-quartz era, but I was surprised by the rectification circuit. People who buy these will buy them to hang them on the wall and forget about it for years, but given the clock's low precision, it will eventually have to be adjusted, so it won't be of any use to the average consumer.
Well in many places you need to adjust it twice a year. A quartz clock. might be three minutes wrong after six months.
@@okaro6595 Wall clocks for this purpose in my country are either radio controlled or have a GPS receiver connected to them. It is mainly located in the hallway on the first floor of a large building. It is a true maintenance-free wall clock.
@@minipolenet well sure a gps/radio clock is better.
they're also more expensive.
a true AC clock mechanism is also more expensive even if it is principally simpler.
Another traditional design is an electronic clock running at 1/60th of the mains frequency (US). Such a circuit would electronically sense the mains polarity and divide it down similarly to dividing down the quartz frequency .
And the grid operators even make sure to run the grid a little fast or slow after there has been an instability of the grid frequency. Just to fix the grid tied clocks!
4:35 You can clearly see one of the main flaws of these el-cheapo quartz clock-movements here --- the gouged line of greenish corrosion on the lower battery-contact pad by his left thumb. That's where the pressure-pads from the battery-compartment press, and verdigris forms in between the pressure pads and the contact-pads. Plus cleaning the pads with alcohol and a pen-eraser only temporarily helps, because no actual metal foil is used here; the pads are merely microns-thick platings of metal, and they soon get worn off down to bare plastic in the centers there after just a few cleanings, and then the battery-contacts can no longer connect electrically with the pads.
I have my grandmother's old mantel clock with the synchronous AC motor in it, probably from the 40s or 50s, and it still works fine. The crystal was broken a long time ago and we haven't found a replacement yet, but the clock itself still works. Compared to that old clock, this one and most modern consumer devices are pure junk. As a kind I never dreamed that a day would come would you wouldn't be able to find good electrical and electronic equipment at a local department or hardware store.
Whats the target demo for this product? Most of the older people who remember plug in wall clocks can get the battery powered ones and most likely said battery would outlive them.
Itâs very odd if itâs meant for the consumer market. Unless someone has a UPS or a generator, changing the clock every time the power goes out would be a real pain-especially with that tiny little dial.
That is ridiculous! After you have paid more for the clock and had the inconvenience of having to plug it in it is also going to be expensive to run! In the UK at 0.4w continuous would cost ÂŁ1.19 a year to run. We can buy decent own-brand alkaline AAs in packs that work out about ÂŁ0.30 each to give more than a year's use. If ever anyone had ever thought battery replacement was an issue they could have supplied it with a lithium AA or made it run on a D cell, either of which might have given it a 5 year battery life. Thanks for the brilliant review video; this entertainment is literally the only useful thing about this clock!
I was used to 1206 SMT resistors having a voltage rating of 50V... but when I looked up the new ones they are rated much higher. Looks like it is within specs. "Vishay has enhanced its thick film small chip resistor in the 1206 case size with a higher power rating of 0.5W and a voltage of 200V"