Video není dostupné.
Omlouváme se.
Design errors in an XR2206-based function-generator from Ebay
Vložit
- čas přidán 19. 08. 2024
- Roger takes a close look at an unbelievably cheap XR2206-based function-generator including an acrylic case-kit from EBay. Follow-up video for fixing the issues: • Fixing the issues with...
Support Roger on Patreon: / kainkalabs
This kit is probably the record-holder in design-errors per component-count :-)
Most of them can be easily solved.
great video. For anyone else who ends up here, it's also worth noting that these kits are offered by various names and prices, but they all use the same schematic. Because of the various suppliers, and also the various component distributors they buy bulk from, results will vary all over the place. But I agree, every issue can be FIXED EASILY. People who complain about a $10 kit cracks me up. Despite the errors, and mods when needed, your still way ahead of the game! Just the xr2206 costs twice as much as the kit lol. Plus you get a component list and schematic! This kit has a lot to offer, and as I said, no matter what, your still ahead of the game. I'm addressing this to the cry babies not the excellent reviewer here.
I used the short screws and nuts in the PC board as a spacer. The case fit perfectly just be gentle tightening the case screws! Great video I'm gonna do some of the mods to it also.
Those days I found your video and it got me thinking (again) about those "irregular" electronical elements (or design flaws) we spot quite frequently in various "chinese" gadgets sold on Ebay and similar. I have a theory - they are made of surplus parts on the market. Those gadgets are made exclusively to sell those elements (very similar as various "sweets" are made to sell us worthless remains in food industry). Let's say a factory somewhere tried to make a knockoff of XR2206, and failed - failed in a way that it only functions from 8-12V. You can't sell such IC to regular customers. They could have thrown all the batch away. But also they could invent a small gadget, a grown up toy, which you offer for a nice price, and people would buy it, because it is so cheap - and makes them feel they are "the real engineers", they have their own function generator (in this case). But it doesn't stop with the IC; the engineer designing it has a task to find the cheapest (not the right) elements for a circuit and make it all work, even so marginally. Maybe there was a big surplus of 1k resistors at the time of making this, and so they ended with them instead of 10k. Many of design features could be from that reason - not so to make a superior design, but to sell surplus electronic parts. To keep the money flowing.
I agree.
I am so glad I found your video. I am learning as I go. I can modify cases, make electrical changes, etc..My weak
point is knowing what values to use and where to connect them. The factor of two with the pots made total sense
to me because I could see it. I just can't "see" circuitry. I am not disappointed that I bought one of these because
I look at it as a learning tool. Because you are pointing out the details, I can make the mods and I think it will actually
give me a better understanding of how it works. Even if it's just a PCB and the tried and proven XR2206, in a nice socket,
for $10 it is worth it even if I have to dig through my spare parts or order the right ones to make this right (with your direction).
Also, I will know BEFORE I build it! That way, all the "wrong" parts can go into my spares, unsoldered, unclipped, and clean!
Yes, I am a "pack-rat" when it comes to electronic components. :-) Thanks, Roger.
This is a tremendous explanation of this device I have learned so much from you! Thank you very much AaND
Great video indeed! I bought an XR2206 from Radio Shack almost 20 years ago. It has been sitting in my parts collection until now. I bought the function generator kit from Amazon. The Radio Shack instructions bear a striking resemblance to Roger's fixes. Probably because they both are doing it right and following the data sheet lead. I'll put my little genny in a metal case formerly used as a data switch. Frequency selection will be by rotary switch and not plug-on. The 100k frequency adjust will be a 10-turn potentiometer with space left for the 1 Meg if I need it. I'll experiment with a non-polar cap on the output. I may put the symmetry and THD adjustments on the front panel. The reverse operation gain can be used the way the instructions call it out as "Attenuation" with rotation to the left as "0 Atten" and the to the right as "max Atten". Switches on the front panel to select sine and Triangle.
I'll post the results when I'm finished.
Oh this is hilarious. Thanks for your brilliant analysis for such a little device!
this type of info should be available for all Chinese electronics actually. disconcertingly this video has 20 dislikes so quite a few people are against useful info. The alternative is to spend 20 hours filtering 90% bulshit from forum pages. VIDEOS LIKE THIS ARE GOLD
@@mendebil Yea, so useful: 'The plastic box on this _SEVEN DOLLAR_ product is slightly too tight and I couldn't _force the screws_ at a 30 degree angle to assemble the enclosure in a way it's very obviously not intended to be assembled. Oh, and _PLOT TWIST!_ When I drive the IC to its voltage limits, rather than just using the obvious 9 volts, it performs out of spec just as indicated in every datasheet ever!!!! D'= Unbelievable!!! Here's my brilliant circuit redesign that allows you to supply waaay more voltage than necessary while pushing other performance metrics out of spec for no practical reason, really at all. Oh, and I'm going take up 45 minutes of your time for this.' xD Very useful. This kind of video is called "nit-picking" and it's very sad.
@@googleblows4016 It's now a Flash deal for $3.99 at Banggood.com shipped free.
@@googleblows4016 If you look at the datasheet specs for the XR-2206, it's designed to take 26v. So he was NOT pushing it "out of spec" at all. The miss-use of all the 'other' component values was/is causing the problem. Yes, it's a very cheap product, but can simply be improved, as he states. It's YOU who are "nit-picking" :-)
P.S. See his follow-up.... czcams.com/video/02XtneCHnDA/video.html
Thanks for analyzing the issues with this little kit!
Actually the integrity of the signals at 1 MHz looks better if you connect a real probe to your oscilloscope!
Maybe. But I think it´s more to parasitic capacitance at low currents/high resistor-values and that the switching transistor is "faster" at higher collector currents.
I had thought about getting one of these, but there are so many issues I think I'll look for something a bit better! Thank you, you've probably saved me some money and some heartache.
I hope you also saw the follow-up video on how to easily fix all the issues :-)
In the mean-time we have added the kit with the necessary extra-parts for optimisation into our shop.
I actually watched that one first!
Awesome Video! I am excited that I found this as I have one of these on the way. Mods to the case, for me, is
no problem at all. Knowing what components to change to make it work better, I wouldn't be able to figure out
myself, or it would take a while to figure it out off the data sheet. (I am at 15:18). I can't wait to finish this video and
go to your next one. You are obviously an expert and I thank you for sharing this information. It , I believe, will save me
a lot of "leg work". Excellent job and video production.
The 4 bolts and nuts that you left out would act as spacers so you wouldn't have to file the case.
That was the smallest issue the case had.
Also the Amplitude potentiometer is reversed (CCW is + and CW is -). Not a circuit defect but a UI unintuitive design.
Edit: ok, you address it in the end.
Thank you so much for this insightful video.
*watch at 1.25 speed :)
I love this man. Roasting Chinese tech industry with passion. I recently bought the same module and was having some same thoughts tho. Keep it up 👌
With my kit I found the best way to use the 4 shorter screws (to secure the PCB to the base acrylic) was to insert them through the acrylic and place the nuts immediately on top of the acrylic. The PCB fitting over the ends of the screws and the nuts functioning as simple spacers. I will be altering the components to accord with your suggestions.
I will try out your way of fitting the pcb into the case because we want to sell the kit with the extra parts to optimize it.
The shorter screws are screwed onto the pcb, the nuts locking under the pcb and not the laser cut acrylic, the protruding ends of the screws from under the nuts, they're seated onto the holes of the acrylic, it just acts as a spacer and nothing more. Wouldn't had been the need for filing the case, to have the power jack fit.
Good display, I like that the triangle appears as a sin when high frequency is used.
If I had to guess the components were probably whatever was cheapest at the time. Ive seen 3 of the exact same board full of all different values before.
I ordered this at alieExpress, IC XR2206 are fake, allso ordered 5x XR2206 didn't work , ordered 3 times xr2206 from Reichelt in Germany , worked right away no problems going over 12 volt., the coarse and fine pots left as is, i use it to clock a SAJ110 for Decap Electronic105T Dance organ , one of the oscillators is broke and works fine , tested it on breadboard only need square wave.
Thanks for your video - I just built this kit.
This is great. You have saved me from having "bad surprises"!
KainkaLabs: randomly uses the term "fiddling around" during the video
CZcams Algorithm: shows "The Best Of André Rieu" in recommended
"to fiddle around" is a normal english verb. Google translate gives "herumfummeln" which is basically correct.
@@KainkaLabs I know, I just thought it was a funny coincident :)
I plan to use this to inject sawtooth and square wave forms into my synthesizer.
I have fed the square and triangle wave to my diy Lpg ! It works well
An excellent review. Thank you very much!
"...it doesn't make fun..." - German detector triggered! ;)
Thanks for a good video and analysis!
The short PCB screws aren’t meant to fasten the PCB to the case, rather they are intended as standoffs from the bottom of the case.
I really enjoyed every last moment of this video! I have built the same kit a few months ago, and noticed a few peculiarities which are all explained very well in your video. I have an Exar databook that has the 2206 (as well as the PDF of course) and as a music/noise maker I have always been curious about it's abilities.
It seems to have the ability to make FM Synthesis waveforms, although I've not made up a board to try this out.
I would imagine a well buffered board with three 2206s and some patching points would be a powerful noisemaker.
I also had trouble with the plastic case. So much so, that I gave up, as I couldn't find the right sized file in my tools.
Please keep producing these great videos!
If you find the time, please make a scan of your notes regarding modifications to the circuit, as I intend to modify mine as well.
I bought two of these from Amazon, one about two yrs ago and the second one a few days ago (December 12, 2023). However, in both cases there were a few parts missing - it seems deliberate to me now - just to save a couple pennies.
The first one, a capacitor was missing, so I had to buy a bunch of capacitors just to get ' one.'
The recent one, missing a single capacitor ( not the same size) and two resistors (I already have); therefore, I'm ordering a bunch again just to get the one.that I need.
For me, It sux buying the kit then i have to buy parts just to get it finished and working. Maybe, they should just raise the price a few pennies to include all the parts.
I'm done with these 'Rip-Off' kits ... I 'm just buying a basic circuit book of circuits that I can build one prototype boards (to practice soldering) or breadboard them.
Very clear. Thanks.
The manufacturer should send you a case of these! Maybe you would say "NO!!" ;-) Going to your follow up video now.
Normally cheap Chinese kits follow the datasheet application example slavishly. Hence many typos and mistakes are also copied. Here I suspect they just wanted to get the kits out and did not care too much. They may have built up one kit, it worked so they were all shipped. More likely they skipped the test build.
i have the same module with the same problems. i took care of output offset by adding an opamp and a potentiometer to create a virtual ground at around VCC/2. now i use that virtual ground and not the power supply gnd for the output. moving the potentiometer i can get some dc offser adjustment.
Nice vid friend. RESPECT !! I learned a lot, thank you. Kind regards, Mich
Thank you for making this video. I learned a bunch. I'm an electronics NOOB, and intended to use this on audio amps.
Very helpful video thanks
Excellent video! After trying to get this thing to work I now won't bother, I'll chuck it in the bin! I'll make do with my £70 FeelElec FY6900 instead. Not worth the hassle to try and make a $10 piece of crap work!
I love this guy. Great vid!
I ordered two of these for the square wave..but the output voltage worries me now 😦
3.3k for the pullup resistor is really the best compromise.
So don´t worry :-)
this is a really cool video
Very informative. However you forgo the fact that this is not the original XR2206 in the kit. Maybe the engineer that designed this kit designed this schematic with other specifications than the original Exar. The IC process used is different. My kit clearly states that the Power supply should not go beyond 12VDC. The Collector output of the square wave needs a smaller resistor because the timing is otherwise not met (at 9-12V). The variable resistors however are poorly chosen. You have a point there. I just built this kit and it serves my purpose. Nonetheless.. Thanks for the video. :-)
you should take a look at the follow-up video where I showed to fix all the design-faults.
Hi Roger ,thanks for the informative video.Would you say that this device as it stands is safe to test a signal in a valve(tube) amplifier at 9v input,bearing in mind that the amplitude pot is the wrong type ?Did you do another video for the corrections ,by any chance?Many thanks and a happy new year.
Sure it´s safe to use this kit for testing a tube-amplifier. No problem at all. Follow-up video for fixing the issues: czcams.com/video/02XtneCHnDA/video.html
i am getting a wave that clipped at the top and triangle at the bottom. why is this happening?
Very interesting!
I just finished assembling one of these and my sine wave looks distorted. Very much like the sine wave at less than 8V here in this video. Not a huge deal, but I wonder if it's fixable.
EDIT: oh, just got to the part where you mention the relevant resistor. I'll try changing that.
Can it accurately generate 1 - 10 Hz and if so, what value output capacitor would you recommend for that range? Thanks.
Depends on what you mean with "accurately" and what signal-shape you need (square-wave, sine-wave?). 100µF usually is OK for 1 Hz if the load impedance is not too small. With 1.000µF you are on the safe side and electrolytics with a low voltage-rating like 16V today are not so bulky as they were back in the days..
from a dsp perspective, i'd have thought highpass filter the output for audio. i don't have the experience or reference for output capacitor.. and i'd conceive it as having a lowpass function, since it's a lowpass without a resistor... but a lowpass does not remove DC offset, sooooo... that capacitor is acting as a bandpass?
Right idk why he said to add a coupling cap on it for fixing the offset ?
Your description of the flaws in that device are indicative that whoever provided that circuit doesn't understand electronics, and went for the maximum profit with no regards for the quality of the product. If a person at least understands Ohm's Law, he or she would think twice before changing component values. No responsible engineer would work in this fashion. How ir comes across is that it was made by some newbie, who kind of knows how to produce a pcb and solder components and just grabbed a schematic from somewhere and gave it a go. If it shows something at the output, that's good enough. Pretty much only amateurs would buy this to fiddle about with some basic applications, so that company has enough market to sell their garbage and make a profit. There is a reason why off the shelf function generators from reputable manufacturers are priced so high. They have actual engineers in charge of the project, the attention to detail is there and it shows, you get proper support and documentation, and the units are tested to a standard before leaving the factory, and the product goes through versions where it gets improvements.
All of that costs money, but that's how a company builds a reputation and keeps their customer's loyalty.
Maybe you can use the PCB, but for the most part, I think it's actually better to just replace all the components for the correct ones, even the ones that are correct I wouldn't trust them.
i would like to have all changes you did it, thanks.
I screwed the 4 bolts into the holes on the pcb with the nuts on the other side. They make perfect posts and the case then fitted perfectly. It's not a bad designed case at all by the Chinese just bad /non instructions.
U are right
Is there a simple modification to strictly limit all output to line levels (2,8 Vpp for 0db consumer level)? Glad I didnt simply hooked this up to my stereo input! lol
For what do you need that? There is nothing like a rule that 2,8Vpp = 0dbU (not 0dB!) is "consumer level".
I Use this kit. But I don't find wave on all output. I can setting the amplitude, but I can't set frekuensy. Can u help me?
Hi Roger, is there a way of combining the lowest 3 frequency ranges into one? I'd like to have a single range of 1Hz - 3000Hz, or 1Hz - 2000Hz and be able to work with it continuously without having to physically change the jumpers in the middle of the operation. Is it a possibility? even at the expense of slightly distorted sine wave forms? Thank you very much.
Maximum frequency range with a fixed capacitor is about 1:1000. For that you have to replace R6 with 1k and the sum of the potentiomeers R7 and R8 must be 1...2 Megohms in total. Consult the datasheet of the XR2206.
@@KainkaLabs 1:1000 may be good enough, I will look into it. Thank you!
Thank you for the excellent details and well made video. I just built and tested the FG this evening and after looking at it with an o-scope I found your brilliant video! One thing I wanted to ask you is whether or not tantalum capacitors such as the ones they included for this kit should have values so much lower than what they ought to be. I test each component before I use them and noticed that they were all rather low. I personally don't know how significant the effects would be but I imagine a lot depends on how it relates to the specs on the XR ic. Lastly, have you ever used the FG085?
In my kit there were normal aluminium electrolytics. I hope you also saw my video about how to fix the issues with the XR2206-kit and the corresponding download-PDF where all the fixes are listed in a circuit diagram.
Are the tantalums lower in value than what is printed on them ore lower than what they should be according to the circuit diagram?
The decoupling capacitor at the power-supply pin 4 is not so super-critical. Even the lower value at pin 10 (internal reference-voltage) is not critical. So everything between 1µF and 100µF should work.
I did get your download. Thank you! I replaced all the caps and only left out the 1 meg pot. The tantalums were just lower than what was printed on them. Probably not critical. Main thing I noted is that when I leave out C9 which connects ground with R2 my amplitude works and if I connect it... then it does not. There are no shorts between the pins of R2 (you had asked if there might be) I ordered 10K pots ALPS. I do not understand what are logarithmic potentiometers and what you meant by needing to rerouted the center pin but I will research that to better understand this. Perhaps I will search for a book on potentiometers. Roger, you make excellent videos! Wonderful detail!!! Thank you so much, Sir.
Check with a continuity-tester, if the plus side of C9 is connected the middle connection of R3 and R5 and if the minus side of C9 is connected to GND.
It must work! C9 stabilizes the output amplitude and should be present.
Concerning log-potentiometers: Wikipedia is your friend.
en.wikipedia.org/wiki/Potentiometer#Logarithmic_potentiometer
With rerouting R2 I mean the following:
I have clipped of all the 3 pins of R2 from the PCB.
Then a made a new connection of the 2 outer pins in reverse order back to the PCB.
The middle pin then has to be connected to that side, that connects to R3 and R5.
That way the direction of rotation is the correct way (clockwise = "louder") and only that way will a log-potentiometer work correctly.
You can see it my video how finely you can adjust the amplitude down to low values.
Think of it that way: With a log-pot every 30° of rotation halfs the output amplitude.
With 270° of rotation you get 9 times halfing the output amplitude which gives a ration of 1:512 between "full-on" and "full-off" (all approximate values; dynamic range only limited by the ratio of R2/R3)
With a linear pot every 30° of rotation only diminishes the output-amplitude by one ninth (30°/270°) or ca. 11%. Further limited to the badly choosen values of R3 and R5
No. I didn´t know the channel of W2AEW.
I basically only watch the videos from David L. Jones from the EEVBlog who is my idol and got me into starting my own YT-channel.
I don´t want to get influenced too much by other videos and just do it "my style" no matter how often the same topic has already been explained better or differently on CZcams :-)
good idea...much like a song writer who does not listen to the radio too much lest he unconsciously copy other musicians styles and melodies!
I get the idea of modding every gadget from China after some time. I get a much better thing in the end. That thing would work great with a guitar signal in and some German glue and American screws.
If you look at the EXAR TAN-005 document (June 1997), which shows the XR2206 function generator application, you will see nearly the same schematic diagram the Chinese producers used.
So they made this function generator based on an EXAR document.
Why do you call it "design errors" then?
First: Circuits in datasheets are mere "suggestions", mostly untested and often mon-optimla or even faulty.
Second: All the points I critize demonstrate that the Chinese buddy who "created" this circuit has no idea of how to design electronic properly and how to "understand" an IC or a circuit. He (or she) could have designed it properly without a single cent additional cost as you can see in te followup-video.
@@KainkaLabs Thank you very much for your answer! I also saw your next video, so I know your good improvements.
Of course there were many things to make better: if they simply had used the EXAR design in the TAN-005, we could have a nice frequency generator with additional sweep input, SYNC 1/2 output, DC adjust, AM modulation input ... using the XR2206 features much better. Only 2 things could be added then: Output with pullup (also AC coupled) and frequency fine tuning.
Production costs: I think nearly the same.
So: no criticism from my side! Thank you for your videos an for selling the improved kit. I only wanted to hint at this old EXAR document for reference purpose.
Hi, from Ireland .I have watched yours long video about this small F.G. , i have 2 of them second one broth by mistake and i have put together one , but i'm not very impressed about . I want to improve a bit and before i watch your video i manage to download a very good book , in my opinion ,written by R.M.Marston :110 Integrated circuit projects for the home constructor if you want i can email you a pdf copy. i also read i can't remember where some people discovered this cheap xr2206 is only a bad copy and we cant do more with this one but i still think if we try we can do better then is at the moment . I will do my own experiment and if you are interesting to see my results let me know .
I'm surprised to see just just 2 comment and 13 like . I have subscribe at your channel , i give you thumb up and i can't wait to see your results . Thanks and sorry for my bad English ,and may be to long comment
I will try to make the best out of this Ebay XR2206-function generator without too much modification.
So at best only change some components and no rewiring (or as few as possible) .
It will probably be ready only after Easter because of holidays here (as probably also in Eire).
Concerning the number of comments and thumbs-up: I do the videos just for my fun (and sometimes for a little bit of promotion of our products). And I do them the way I like to and I don´t care about the "rules" how to get a many subscribers etc.
Sometimes few comments also means, that everything is explained fully, correct and understandably :-)
Anyway the ratio of thumbs-up and thumbs-down is quite OK for me and that´s more important than the absolute number of thumbs-up:-)
i subscribed! more ebay modules please
I have tested a few more Ebay/AliExpress modules like a MAX038 function generator, Air-Quality monitors etc. Please tell me specifically, what modules you would like to be tested.
hello, can I generate a 6Vpp sinusoidal signal at 1khz with this generator? thank you very much!
Yes, if you implement my tweaks in the follow-up video.
stimmt nicht das gehäuse passt aber man sollte die platine mit schrauben und muttern versehen und nur reinlegen so das die muttern als abstandshalter zur unteren acrylplatte dient dann passt auch der ausschnitt für den stromanschluss aber das muss man erst herausfinden und meine löcher passten sonst soweit
Danke für den Hinweis.
Werde es mal ausprobieren, da wir das Ding mit Bauteilen für die Verbesserung in unseren Shop aufnehmen wollen.
Antwort in Englisch wäre hilfreicher für die 90% englisch-sprachigen User dieses Kanals/Videos :-)
Hi, I have searched a lot and experimenting with this xr2206 kit and with different schemes with split power supply and with single supply just to try to figure out the jittery problem when you increase the voltage. Today I read this forum.allaboutcircuits.com/threads/problems-with-a-xr-2206-function-generator.101369/page-2 and I decided to find out if this issue is about fake xr2206 bad copy or something else like we missed something so I tried all my stuff of xr2206 ,about 6, and all have the same problem but with small differences in the power supply. In this point I decided to open my Elenco closet-700 analog/digital trainer and use this XR2206 which is 100% original and yes with this I can vary the supply voltage and the waves isn't affected at all . Case sorted. Now we can use this Chinese with few modifications as is or try to get original XR2206 which probably costed more than the full kit . I still can't wait to see your results. Good luck and Happy Easter to you and all yours subscribers.
You are right. I´ve had the same result. Must be a fake XR-2206. I will compare the IC and an original EXAR one under a microscope next week.
It even looks like the component values they choose are specially "trimmed" to the fake Chinese XR-2206.
For example changing the pullup-resistor for the square output to 10k made the square wave worse from 10kHz upwards.
Most important for me was that I could fix the amplitude settings with a 10k log. poti (with reversed terminals) and changing the resistor-divider R3/R5 to 1k.
🌹👍
They already did everything they could do wrong XD that was funny
I guess they want to make You feel You are getting more by slapping an extra knob on it to give t a cool factor lol
Does anyone make a signal traced kit ?anyone.
THE XR2206 CHIPS IN THAT KIT IS A FAKE COPY CLONE.
And I subscribed....
99% of these have a counterfeit 2206 chip. Can't handle voltages over 12 and will likely fail within a few hours of use.
It´s 100% counterfeit chips with these kits :-)
Probably some chinese housewife wanted to start a “business”!!!
The XR2206 in this kit is a Chinese locally manufactured FAKE that has severe limits, including voltage being limited to
Well, except for the 12V supply-limit the behaviour is absolutely identical to the original Exar-IC. The stange component-selection has nothing to do with the copied chip-design. It are, as the title suggests, design-errors by whomever made this circuit.