Seven Decade Programmable Resistor - A Low Cost Solution
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- čas přidán 5. 09. 2024
- gerrysweeney.co...
I have spent a lot of time over the years prototyping electronic circuits and the amount of resistors that have ended up in the trash because they are so cheap you don't bother to keep them tidy or organised once you take them out of their organised storage. One potential solution to this is a programmable resistance box but the problem with these things are they are bulky and expensive and do not lend themselves well to breadboard prototyping. The cost of construction means they are typically the reserve of high-precision resistance boxes.
I spent some time looking at options and what was available but did not find a solution that met my own requirements so I ended up designing something simple and decided it was probably worth making some of these ready made available for others.
Thanks for the comment, glad you like the idea. The point you make is spot on, its a lot of trouble to go to for a one-off but at this price point its a ready made solution that you just buy and use - I would have bought these when I needed a solution - I was hoping others would find them useful. Gerry
Hey Martin, thanks very much for sharing, appreciate it, and thanks for buying too, glad you like it. Hope your all settled in over in the US now, nice to see you back reviewing again. Gerry
Hi Ian, thank you for your comment and your purchase, will be in the post tomorrow. Glad you like the idea - I was also surprised this has not been done before but perhaps its just me and you that think its a good idea :) Gerry
Thanks Gerry. My order arrived earlier today (in Seoul) and I feel they're indispensable tools already. Great idea done well!
Love that old decade box! They don't make 'em like that anymore. Contact resistance in the pushwheel switches could be reduced with a good contact cleaner/lube before assembly. I plan to build one but I think I will use .1% 1/2 watt thru-hole resistors instead. More expensive but a bit more magic smoke resistant.
I don't get why people are thinking .1% resistors are more accurate than 1%.
They're only more accurate when you buy the exact amount you need and don't care to measure them before use.
The production tollerance means that when you pick a random resistor, it will indeed be within the given tollerance.
However, if you're hand picking resistors from a 1% batch you can get even better accuracy than using random .1% resistors.
I'd rather get 100x 1% resistors for the same price as 1x 0.1% and pick the best ones to use for a decade resistor project.
Yes thats a reasonable suggestion that would work too. I took this approach because I wanted to use all of the same resistor types, cutting the track was easy enough. Overall though the thumbwheel switch solution was not perfect. Thanks for the comment and suggestion
Gerry, new to your channel and like your set up. I too have made a decade resistor unit using the push button switches you've show, its limited to 1/4W due to my choice and physical size of resistor, and I think it wont be too long before I drive it over current by accident. I've order one of your units, great idea, so simple and compact and handy to have the greater current limit - Good Work that man!!
I really like the size, convenience and cost of this resistance "box", cheaper Chinese knock-offs notwithstanding. I just sent you a question on eBay about it as I couldn't see for sure in the photos whether it had banana sockets or not. Banana sockets would make it just perfect for me.
I'm planning to make a passive step sequencer for my synth (which uses banana patch plugs), passing the voltage from one of the patch points of the synth itself through a controlled set of resistances before patching it into the pitch input of the oscillator, and this is exactly the kind of thing that will make finding precise resistor values for different notes a walk in the park. I might add trim pots to my design, but I quite like the idea of making my design so precise I don't actually have to, and doing that by testing resistance values with a combination of two resistors at a time - fun though it is - would probably take 100 times longer than using something like this.
Just after writing the above, I see I was distracted during the point in your video where you mention banana jacks as an easy add-on, so I'll just go and do that myself when I get one. I've ordered one now.
Thanks for the feedback and the order and of course the support. Yeah, it did not take long, as soon as I started selling these a few Chinese companies also started making variants. that's the global economy for you :)
I built a pushbutton decade resistor box using the exact same switches as yours, but your jumper based one beats it hands down for convenience around the breadboard. Why has nobody thought of this before!
Thanks James, yes you are exactly right, thats the suff. Thanks for your comments. Gerry
Thanks for the feedback, yes you are right about that :) I will get the technical info document updated with the parts and PCB layout. Gerry
There certainly are, although good quality ones are more than $2, and then you have the bulk size and of course once you have switches you need knobs to indicate position, and a front panel of sorts (perhaps the PCB) to show the markings. It gets complicated quickly. Gerry
Those digital pot chips are essentially MOSFET switched resistors and are not truly passive so would only work in certain use cases. A true programable resistor is electronically a purely floating resistive element so the only way to make an electronically programable resistor would be using some kind of electronically controlled mechanical switch (relay, rotary switch etc).
Thank you Denis, thanks for watching. Gerry
You must of been reading my mind. I always thought decade boxes cost a fortune, I can understand why, if you need precision. But just for prototyping you just want a quick change and within the tolerance your circuit will end up with.
I will end up buying a few of these, at that price there's not much point me making one.
Another thing too, if someone wants to put a switch on a range or two they could just put a female header on the switch. Nice thinking Batman. :D
Hi Kevin, thanks for the support. Gerry
Yeah thats a nice idea, it could be added as well as the terminal block so there are both/all options. I did think about sending Dave one, I will get done with the inrush first, a whole bunch have sold on e-bay that I now have to get packaged and posted.
Excellent work Gerry, thumbs up, shared..and purchased. Cheers, Martin.
Nice idea and good looking end result. Ordered 3 today.
I had 200 of them made, that took 18,000 resistors. The cost of boards and components is actually very low, is the cost of assembly then shipping, import duty and VAT that hikes the cost. You need to get into the 1000+ to make assembly costs reasonable. If there is interest I will get more made. Regardless, it was a really interesting exercise to go through the process. Gerry
Great idea, unfortunately ebay doesnt ship to my country and I also dont have any credit card!
anyway i love your idea and i will build one myself, thanks for sharing.
Thanks for your comment and thanks for watching. Gerry
Thanks for the feedback. Gerry
If you want it truly passive-resistive then there is only one option which is to use relays, and a lot of them. It did think about creating a servo driven switch of some sort but things start to get complicated and expensive very quickly !)
Great presentation. Thank you for your hard work.
Good suggestion, thanks. I will keep that in mind for next time. Gerry
Excellent video! Your soldering is far neater than mine!! :)
Metal foil resistors.
Capitulo 1.
Resistencia de film metálico, película delgada o una lámina de un material resistivo conductor de electricidad. Metal foil resistor.
Capitulo 2.
Análisis de los puntos técnicos redactados por Reuven Goldstein and Joseph Szwarc.
Capitulo 3.
Capitulo 4.
Maquinas y sistemas de producción.
Capitulo 4-1.
Sistemas ópticos.
Capitulo 5.
Operaciones a realizar.
Capitulo 6.
Principios del metal foil resistor.
Capitulo 6-1.
Substancias y materiales utilizados en la producción del metal foil resistor.
Capitulo 6-2.
Metal foil resistor. Kodak Thin Film Resist (KTFR), y la radiación ultravioleta.
Thanks, thats really great. Glad you like them. Gerry
Nice work! I think the sheet you're referring to at 4:40 might be Tufnol.
Hi @HWGuyEG, I posted a forum topic on EEVblog as you suggested. I will think about getting it into one of the on-line stores, I will send a few e-mails and see what transpires. Thank you for the suggestions. Gerry
I don't know what a pound is but I bet that thing would be worth shipping anywhere I got a small one but a couple resistor are burnt and who knows what it went threw till that thanks for the info
Wouldn't digital potentiometers be the solution (non-volatile ) ?
If you get them in single (8bit) format they can be MSOP 8 . Make a small board for it so it will have a normal 3pin output. And have a base stations (simple micro + lcd + buttons) that can program the small digital pots by holding it on a jig / pins or something. Of course you are power limited but for the non power applications it would be awesome.
I will be ordering one asap as I like to repair electronics and feel this could really help me out. Thank :)
Thanks for the order, much appreciated.
Thanks Jerome, much appreciated. Gerry
Brilliant really. I just ordered one. Thanks!
I don't like the thumbwheel construction at all personally. Not that I have had any significant experience but certainly the thumbwheel switches I used were pretty crummy and were sometimes not making perfect contact.
I aking if anybosy know you could make a resistance eletronicaly like happing in the multi calibrato calibrator?
The big clunky switches were actually mass produced back then, a whole lot of precision instruments were much more common back then, and they all used basically the same ones. Btw. you could have avoided cutting the track by using a tth resistor instead of a link wire (built the same box a while ago from 10MΩ to 100mΩ). IMHO using 1% resistors for it is worth the extra money even on the cheap thumbwheel thing. What I never liked about the jumper based ones is two things. Once, when they age, they tend to have much more unreliable contact resistance than cheap thumbwheel switches. Secondly, it is much harder to see at a glance what it is actually set to.
Dennis Lubert thanks for your comments, and for watching. I have found the jumpers to be reliable, and when they age either squeeze them with pliers or replace the jumpers, they are very low cost. I do get where you are coming from although when I tested the cheap thumbnail switches they were far from perfect, at least the ones I had played with. Gerry
Legibility issue is simply a matter of colour, the jumpers don't have to be black, they could be bright yellow.
Siana Gearz The issue is not the visibility of the jumpers themselves but that you can see the complete number easily in thumbwheel switches but have to count jumpers
Gerry Sweeney Hm, looks like I haven't seen your comment in all the time... there are really many different thumbwheel switches (as there are probably jumpers too) and its certainly a price issue too. There are high quality ones, e.g. those built into the RS-201 precision resistance substituter by IET, one would guess they have at least gold plated contacts. Same could probably go for gold plated jumpers/pins. The problem I have with "When its bad contact, replace the jumper" is that usually you don't notice that its a bad contact. You have a couple of Ωs too much resistance, but since you rarely measure your decade before using it...
Great idea, well done.
I ordered one. I await the multi bank one :D
Looks great, going to order one asap
Thank you, appreciate it. Gerry
Am going to bye one next week love it . I need to find the right ohms to tap in to my car in take sencer . At the right ohms with a relay to ground it can trick to ecu just for a bit and u can pull timing out of your cars engine.
It's for using nitrous . Anyway I need a box like the one you have made but I really only need to go from say 100ohms to 56k . Could u do me a box with just 3 or 4 instead of 7. If not it's cool . I take It I put the pin in wear or what I need .
Sorry 1st time I have seen this type of seen the box kit type bit u have to build that yourself . Wear with yours I can find the right ohoms I need to trick the ecu . Then get that one from a shop .
so simple great idea
Well done!
Hi Mark, thank you for your feedback, glad you like it. I have them for sale on e-bay but I am waiting for more stock, the first batch sold really quickly so it took me a bit by surprise. You can search for "gerrysweeney" on e-bay or on tin die(dot)com. Gerry
thak for the help.
Brilliant!
Another site you might want to consider selling on is Tindie.
The time electronics decade resistance boxes use a very similar construction (to your first protoype) with thumb wheels but use precision through hole resistors rather than surface mount. The single board with jumpers is absolute genius.
TOPCHANCES ZX21 Decade Resistor
Can u make me one of them if was to pay you of course if seen kits for sale on eBay that have to be put together. But I need to test things from 100ohms /200/350/500//600/1k & so on up to about 56k
can you make one with higher power rating like say 100W
??
Well I suppose but it would be very expensive and you'd use much lower value capacitors. P = V^2/R so to get 100W at just 30 ohms you'd need 55V in a dead short through the box. As well once you start carrying higher power like that not only is 100W heat dissipation an issue, but you have to start to worry about the contact quality and possibly even arcing. At that point I'd probably recommend you just make a dummy load around a 100W bipolar transistor.
And another thing, haha. Would be nice if you could make a board with a bank of 3 or 4.
garry i beg you yes i beg lolol sell me one,,it must come from you
,,garry al tel yer thats bril,, am a new fan,,,but on just 3 videos i have seen
and now i have to se the rest,,,top stuff garry,,,,,,,,,,mark,,,,,,,,,,,,,
Well if enough people are interested in the single one, I will see what I can do :)
Dumb question anyone? What is make before break? My old eggshell mind is thinking break before make... maybe I need to change my work habbits.
It "makes" the next contact before it breaks the previous contact......hence it retains continuity.