Fixing the issues with the XR2206 Function-Generator from EBay
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- Опубликовано: 19 апр 2017
- This is follow-up video to • Design errors in an XR... where the design-errors are demonstrated.
Support Roger on Patreon: / kainkalabs
This video is about how to fix them and make a really useable mini function-generator out of the badly designed 7$ Ebay XR-2206 kit.
A user has commented that the used XR-2206 is probably a counterfeit chip.
This is confirmed here live by exchanging the chinese-supplied XR-2206 chip with a genuine one.
Download of the schematics with the optimized components and instructions:
1drv.ms/u/s!AmW9-q-1GZM1ip5wO... 
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really a very detailed and complete review with solutions and again an example how good original electronics get messed up and quality undermined by the chinese vendors trying to compete on price. You have shown the world with a little engineering to get right. Thanks again since I have this original XR 2206 function generator from more then 20 years. Not surprisingly it still works. It is fun to see this Exar Co. survived all the turmoil and that the Chinese still can make a few buck with their name. Thanks again Kainka. We need this sort of review.
Sorry Tom B., Things are not that simple as being shown, as there is more to. There are two main problems with the XR220 and the one it shares with the Intersil 8038. It's the Square wave resistor - it makes no difference the size as using af resistor "kicks back" into the curcuit. The other problem with the XR2206 comes from the switching across the capacitor. The real switching time is approx. 35 nS but that's not all, it's the loading and discharge cycle that coarse the problems. When the loading cycle nears the top - and before the switching occurs the opening of the transistor is under way - beginning to discharge whike charging which gives a spike or notch in the top and bottom af the triangle that is used to from the sinus. This is all internal and can't be changed from the outside. that was the technical level at the time these curcuit was produced. - Please mark the frequens you are shows - less than 20 KHz where it is hard to observe, with higher frequency it becomes more visible and dominant.The Intersil can produce sien and triangle from subzero til 200 KHz flawless, and if you then take the sinewave and convert af part from this to squarewave, you can build a very nice working functions generator.
I would love to see a decapping and reverse engineering of the fake vs the real chips.
I hooked my XR2206 eBay Function Generator up to my scope, and observed a bunch of weird problems. I went searching for information about this, found this video, and experienced the most efficient 38 minutes of electronics schooling I've ever had. Thank you, sir!
Your schematics are gorgeous. Thank you again for going even beyond what is needed to make this thing work.
I love tweaks. The closer it is to optimal, the more I like it. You did all the hard work. KainkaLabs, give this man a raise.
This sets you apart from the rest when you come up with the fixes to correct something and make it better thank you
thanks for the two videos. Very detailed. I had also bough the same kit. I just wanted some function generator for playing around, but even the sine wave did not look that clean to me. So I bought a used GW instek for a little bit more. Didn't realize all the problems you showed. Very nice.
Excellent debug of this unit! I built quite a lot of 2206 chipped oscillator units for the Audio recording studios I worked at. These had 5 fixed sine wave frequencys selected by rotary switch in order to set up analog 24 track tape machines for Bias, record levels and playback tones.
Original EXAR data sheet seemed spot on for the low frequencies 50hz~20Khz sine wave used. This Ebay unit looks good after your work!
This material is educational GOLD. Your descriptions are easy to follow and academically dense. Subscribed and liked. Awesome. Jonathan in Seattle.
Good rundown of the problems and solutions for this circuit. Two areas I would disagree on:
1. I don't like the idea of using input protection diodes to compensate for driving logic with too high a voltage. As you suggest to an earlier comment, a voltage divider would be the easiest fix although a proper level shifter would be better
2. It seems unlikely that the real XR2206 would improve the output square wave at high frequency with a 10K for R1. The output is open collector and the slow rise time is due to the RC time constant formed by R1 and whatever is connected to the square wave output (including parasitic capacitances). If the real XR2206 really is better, this suggests large stray capacitance in the fake part.
I'm glad I found you. My sinewave as you have shown was a bit distorted. I'm gonna do your method of repair. Thanks from Australia🙂
I bought one for audio applications and this video is pure gold
Very good explanation and useful information thanks for sharing, I will check this out tomorrow and make some changes.
Thanks a lot. Very useful information and a little kind of work that an engineer must do when a problem is on the road. At company I work I see this kinds of troubles when a cost reduction is implemented on products we manufactures. Best is to buy to OEM ICs ever.
To be fair the Ebay sellers mention that the circuit works only up to 12 volts.
And the XR2206 is not produced any more by EXAR for a long time and genuine/OEM/NOS parts are totally overpriced at Ebay.
An excellent and very informative presentation. Thanks very much!
Daniel from Ireland. You are a HERO!! Thank You.
Thanks! Very interesting the subject made available.
Thanks Kainkalabs. (ROGER). This was very helpfull. :). I made the functiongenerator with the options you give me. Right from the start. Thank you very much. Paul from the Netherlands.
Awesome. This is super helpful, and I can now use this generator to test tube amplifiers that I build!
Wow, pretty cool. Thank you (and the people who gave you some feedback on various issues) for this. I just bought one and will definitely be double checking everything. I bought the thing mostly for 1)improving my soldering skills, 2)testing a soldering station I bought as a present for my dad and 3)I will use this a wave generator for a basic synthesizer I would like to build to learn more about this type of instrument. For this purpose I want to go as low as possible in terms of voltage and also cover 20Hz - 20kHz.
I guess as usual it is safe to assume that there is a 99% chance for an IC to be fake when it's shipped on Amazon, eBay, Aliexpress etc. from China. :D No surprise there.
I notice theres no mention whatsoever on the one page info sheet of the need or function and their freq coverage of the five pairs of paired header pins. Also mine too has no brand logo on the IC itself, just ordered a branded replacement. Thanks for posting this, an excellent way to learn practical electronics.
Thanks for the videos. I still have my kit in the original package that I got a few weeks ago. I'll have to open it up and see if they made any changes to it. I kind of figured that the chip was a fake since the same kit with the case cost me $2.83 US dollars delivered. I always build these Chinese kits on a breadboard first to make sure they work as advertised or to test my own mods to the kits.
Great vid on this oscillator, it's a perfect fix, thanks! One suggestion i have would be to connect a 100k resistor from C10 negative to ground. This will keep the C10 capacitor charged during operation, thus keeping the DC off of the output at all times. The 100k will have negligible effect on output loading.
Many thanks for this and the earlier video. I have just bought one of these kits and after the initial jubilation of it "working" started to notice all the issues you mention. The one that is really bugging me is the frequency instability. With the chip I have I can't find any supply voltage that gives an acceptable level of stability. So I am now out looking for an original part that I can get in the UK. Still at least I know what the problem is. So thanks again.
Thank you for the video! I am finally getting around to building my kit. Ideas: 1) I will be using individual socket pins, cut from strips, for the discrete components that can be changed within a range of values to tweak the performance of the circuit. 2) A followup video about any new thoughts that you have about the project would be great. 3) Adding closeup photographs of your adaptations to that video would be very helpful to us, to devise our own configurations. If you are not interested in creating a new video, maybe you could take individual photographs of the said adaptations, post them somewhere and give us the link to them. Please and thank you.
Thanks Great video !!! Very detailed. I'm buying one now..
This was very useful. I've swapped R3 R5 and the amplitude is much more useful. Just need to get the A10K pot now and I can fix the rotation too.
Thank you for your hard work! I bought this little cheap kit to help me learn how to solder. Got it "working." Now I am using it to help me learn how to DESOLDER! 😂I will come back and try to test some of this out on my breadboard once I get the parts out.
I was able to remove all the components and only destroy one cap in the process! That was a few weeks ago, today I assembled the chip on my breadboard and was able to wire up the Basic Test Circuit detailed in the data sheet for the XR-2206. Next -- finalize a new design, test it out and finally solder components to a blank PCB. Cheers!
I finally rebuilt the XR-2206 with new components on a double sided proto-board a few weeks ago! The sine wave doesn't seem to work, but the square and triangle waves will do! All in all this was a very educational journey. 😬👍 (I also built a 4 channel audio mixer to better listen to future oscillators and filters I will be building.)
By the way THANK YOU FOR A VERY INSTRUCTIVE/ INFORMATIVE VIDEO !!!
Thank You for giving the fixes
Very informative thank you, great tutorial
Hi,
Thanks for the very complete and comprehensive videos! I also found another issue that is wonder is somebody else had:
In my signal generator the maximum possible amplitude is around 3.5 volts (peak-peak) and no matter what I do stays the same. I changed the amplitude potentiometer for a larger one but the issue persists.
Any hint of what could be the cause? Thanks!
Wow, good catch ! Many of these generators were sold as 9v dc powered generators.
Yes, 9V is "save". 12V is the maximum supply-voltage for these rip-off XR2206 chips.
Great analysis! I will try to build mine accordingly.
There is just one problem. The JYE-Tech DSO150 I have yet to build wont help me adjusting the gain control.
Is there a useful fixed restistor value for R4 that I could use?
from the image of the pub in your video it looks like you have C9 soldered to the side of the barrel power plug for the negative connection which I also did. I also ordered a genuine XR2206 from Jameco just to compare the results.
Great video and explanation.
( good sleuthing "Daniel from Ireland" )
Great video! i was wondering if you have played around with the fm pin on this IC chip. I was considering using this board to make a sweep generator.
Unfortunately not
Круто! Я то думал -- почему у меня xr2206 не работает... Спасибо за рецепты! Буду пробовать))
Counterfeit components on EBAY? Who would have thought that? Thanks for an interesting video, I live in SE Asia so it'll be difficult to find an original chip. We have counterfeits of everything from chips to Toyota vans (no joking).
Dont ever buy seeds from China either. None will germinate.
@@michaelwaxter3372 Or they may grow something really strange and of the wrong "value". Corn beans or asparapeaches. ;-) (Why didn't spell check complain about "asparpeaches"? Oh, there it goes. Phew, I thought maybe that was a real thing! Scary. :-0 Cheers, Mike!
Very nice and informative video indeed. Many thanks.
Just a question though, which minimum frequency could you get to in "square wave" mode?. Is it really possible to get down to below 10Hz?
There is no reason why it´s not possible to get below 10 Hz. If you are using an output capacitor to get an AC-coupled signal, the value has to be quite large (>100µF)
Excellent. Thank you. Is there any reason that R1 could not a be minimum 1K Ohms and a 10K pot added to it in series, so that the sum of R1 could be trimmed on-the-fly, as the frequency requires?
thank you very much sir..
Very informative thank you
0918, and 0919 seem to be the magic numbers on these currently available Exar chips. I initially bought a couple on eBay two years back and a recent one from Tayda (all say F0918). I still have a hard time believing that Exar suddenly puked out a billion of them in two specific months despite being in production for so many years.
FWIW, I didn't seem to have the voltage issues with mine, but I couldn't get an op-amp based virtual ground to work without losing the negative side of my output wave. Could have been the circuit, but it came from a schematic which was mass produced as a kit, so I'd imagine someone had a working one somewhere.
- and thanks for the great videos!
make that two specific *months*
duh- make the months weeks ;-)
I think the XR2206 from these Chinese kits must be counterfeit-chips.
So you probably can´t rely on the date-code but have to rely on the reputation of the seller if you buy a replacement XR2206.
There are some RUclips videos out that the Chinese even fake the 555-timer chips!
Someone has decapped them and compared to some original ones and found some obvious differences in the chip-layout :-)
KainkaLabs- This recent one was bought as an individual component from Tayda Electronics. I inquired afterward about getting an older one, and they were very helpful and seemed interested in seeing that they weren't buying counterfeits. They said they tried to get 0918, as they had reports of problems with 0919 chips they bought. I just have a weird feeling that, unless someone grabbed a big pile at a government auction or something, anyone who's obtaining enough to be selling them in 2017 is probably getting remakes or we'd be seeing a much wider range of date codes.
On the plus side, maybe the Chinese will be tweaking them as more people become aware of the "undesirable qualities". When I checked, mine went up to 18V or something before it got shaky, so it doesn't appear to have that problem.
Very interesting. THX for the info.
The Amplitude VariableResistor is also reversed. Turn rigth amplitude decrease, turn left amplitude rise. The coarse and fine variableresiator are fine.
We modify the pcb trace to fix the amplitude variableresistor issue.
And
The 10KOhm rv09 variable resistors are not available here, so just use the original 50k one in parallel with 12KOhm or 13KOhm resistor.
Thankyou uncle Rogers. Bye bye from village labs..:)
HI There, Very good explanation and testing, thank you.
Is it actually be set as positive offset frequency?
Could you explain your question a bit more clearly. I just don´t get it.
6 years later and this is still incredibly helpful! Thank you so much for the time and effort you put into this. Tracking down components for the upgrade now!
not even because the url provided doesn't work anymore...
New link: 1drv.ms/u/s!AmW9-q-1GZM1ip5wO7uvHpcenfI14g?e=m4TqeJ
Did you actually try the authentic XR2206 chip with regard to the square wave output issue? Because that is exactly what you should expect to see as you vary the pull-up with an open-collector/open-drain output. Your scope input is presenting a capacitive load which the pull-up resistor has to drive, so the higher the resistor value, the longer the time-constant. The reason it appears to be frequency dependant is that you are changing the timebase on your scope and just looking closer and closer at the rising edge.
Note that the falling edge is not effected because the output drive transistor determines this, not the pull-up.
A better way to condition the signal for lower voltage logic would be to replace the simple pull-up with a voltage divider so that the peak voltage is limited by the voltage divider ratio. The effective R with respect to the RC time constant then becomes the _parallel_ equivalent of the two divider resistors (Yes, even though they are in series with respect to the supply, they are in parallel with respect to the output) This will substantially lower the RC time constant, and improve the rise-time. Also you will not be relying on the digital circuit's input protection diodes to limit the voltage, so the input current limit on the digital logic is moot.
Yes, it was a genuine XR2206 from EXAR.
Hi, Roger! Thank you so much for this video...it was extremely informative! I especially liked your improvements, and the schematics you provided with the changes. I made all of the modifications you suggested, and they all worked except for wiring R7 (changed to 10MOhm) and R8 in parallel. I may have mis-wired the pots, but changing R7 didn't seem to make any difference. I reverted back to R7 and R8 in series and it works well enough. Also, I replaced the supplied/fake XR2206 with a genuine XR2206 and it seems to work better, but I still have very narrow noise spikes at the maximum and minimum of the sine wave. The spikes are present with both the genuine and fake XR2206 chips, so I wonder if the problem is being caused by another component (one of the caps)? Also, I was able to source all of the replacement components from Jameco (in the US) for $11.73 (including a genuine Exar XR2206). Not a bad price for a significant upgrade! (I will make a separate post with the Jameco part numbers and prices.)
The spikes at the upper and lower limit of the sine-curve are a consequence of how the sine-wave is created inside the XR2206. It is a well-known bad "property" of the chip. Soon after the chip came out some clever engineers developed some "workarounds" with a lot of extra-circuitry to get rid off or minimize the spikes.
@@KainkaLabs Ah, that makes sense; thanks for the explanation. After I looked at my board again, I realized that I forgotten to solder in C9, and I thought that might solve the problem. It did stabilize the signal a bit, but didn't get rid of the noise spikes (obviously). The spikes really distort the sine signal badly above ~100kHz. It's notable that the closer you look at the performance of this chip, the more flaws you see (the noise spikes, bad square wave asymmetry below ~100Hz, etc.)!
Another possible solution to the square wave problem is to keep the 1K resistor and clamp the output with a 5.1v Zener diode. I have one of these kits but not built it yet, so I may try that as many 3.3v logic devices are 5v tolerant these days, I just don't know if a Zener would be fast enough at higher frequencies.
I am a bit late to this party, but I learned a lot from your video and will apply these improvements to the kit I bought online. I was curious if you have also looked at the 8038 kit(s) that are out there? I bought the one that comes with the acrylic case, but am quite disappointed in it. The problems are so numerous that I doubt I will even attempt correcting them. However, there are a few other 8038 based kits, so I may try one of those as well. I'm looking at these more from a learning perspective than an actual user perspective (although I definitely will use both of them). Thanx again for some great videos.
I only recently discovered by chance that there also 8038-based kits available.
I haven´t checked one yet but perhaps will buy one or two and try them out.
Will be interesting to see if the Chinese also fake the ICL8038
I have built several 8038 circuits, and they are fairly limited on frequency range. But for an audio generator, it works quite well!
Hi, just a quick question, I'm ready to assemble the kit and I'll implement all your suggestions with the exceptions of using the fake IC and for R2, I'll use a 10K linear pot (which I already have). Will there be any negative effect to my output due to those deviations? Do I need to change the connection of the wiper like in your diagram having a linear pot in R2?
With a linear pot you don´t have to rewire the connections because a linear pot is symmetrical (while a log-pot is not symmetrical concernings it´s outer connections)
The only thing that remains a bit annoying is the counter-intuitive rotation.
I love your work with this chip. After making these changes, have you thought about a way to make it sweep from one frequency to another ? I have a need (radio testing) to make it sweep from about 200 hz to 5000hz and be able to view it with an oscilloscope.
You need an extra-circuit for the sweep-input of the chip. That doens´t fit any more onto the PCB. Today you can get relatively cheap function-generators with a sweep-function. Or you google "XR2206 sweep generator" or similar to find examples of the necessary extra circuit.
Great video! Is there a way to do phase shift for this one? Say I have two of these and want one of the two shift 90 degree.
Not that I know of
well explained with real test thanks
good information, the link for the schematics and optimized components list does not work.
Hi, I try to find the authentic XR-2206 but can't find one. So have you got any suggestions for me to get the real one?
Many thanks for this helpful video!
Try ebay or octopart.com or findchips.com
Jameco claims to have them. www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?refineValue=EXAR+Corporation&refineType=String&langId=-1&productId=34972&catalogId=10001&sub_attr_name=Manufacturer&storeId=10001&krypto=zF68DEtssBD5VI%2BVlv9RkZh%2BVo6y2pPGE86qDzbwZau20vajWZQm%2BC%2FalG5uGVDV1kLn6ef%2Fg4YnA6C%2FqO%2F77A%3D%3D&ddkey=https%3AStoreCatalogDrillDownView
Very good explanation. I made some changes you suggested and works like a charm. Only problem is that square wave amplitud is not adjustable. Can you make a high frequency (up to 500KHz) Amplitud control for the square wave?
In theory with an adiitional potentiometer at the output of the square wave. 1...10 kOhm resistance value should work.
@@KainkaLabs Thank you for your reply. Based on your theory I implemented with a 5 kOhm potentiometer built-in in the kit and works perfect. For your reference I made this video:
ruclips.net/video/UP1W4SsdEPI/видео.html
Thank You.
It's good that you showed the difference between original XR 2206 chip and the "fake Chinese chip". I wouldn't want to rely on Chinese chips if I don't have to.
Yeah, but genuine XR2206 are very expensive now and only available NOS on Ebay. Nevertheless below 12V the Chinese counterfeit behaves mainly the same way as the original chip.
I noticed that in your video comparing the DSO138 scope that your scope and numeric values on the screen with PPV and others. Mine does not. I built it from a kit approximately one year ago. I believe the software is upgradable and so I hope that I can add these features. Also, do you have a way to receive donations to help support your video making? It is tough to continue and I know that some whom I like take Pay Pal contributions. Thank you, Roger!
Remember that the display of the numeric values can be switched on and off:
"Press [ SEL] so that t imebase is highlighted. Hold down [OK] button for about 2 seconds. This will turn
on/off measurement readouts."
Firmware for the DSO138 can be found on the Jyetech homepage:
www.jyetech.com/Products/LcdScope/Firmwares_138.php
How to upgrade the firmware: www.jyetech.com/Support/HowToUpgradefirmwareByBootloader.pdf
Perhaps I will create a patreon account for donations.
I hate the monetarization-function of RUclips videos.
1.000 views give you 1$ if you monetarize a channel.
That´s not worth the annoyance for the viewers concerning my very-special-interest channel with ca. 1.000 subscribers.
Thanks for this video, KainkaLabs. I put together this kit and followed your improvements. The square wave looks good even at high frequency but I find that the sine/triangle output has an offset of a couple of volts which does not seem reasonable. Has anyone else had this?
If you use the electrolytic (10...100µF) at the output to get an AC-coupled signal and only probe it with the 1 or 10 Megohm input impedance of your oscilloscope, the initial DC-offset discharges only very slowly with a time-constant of R*C which is hundreds or thousands of seconds!
Put a 10k resistor to ground behind the electrolytic and the DC-offset will be gone more or less immediately :-)
Thankyou, yes, i clearly didn't listen closely enough to your video :)
Good day. I am thrilled with your instructive video. I had the above kit with XR2206 so I decided to apply all your recommendations. BUT BUT....I have some problems.
1. I can't regulate the amplitude at all. It's at maximum.
2. I don't have SINUS and TRIANGL signal shapes at the output. I only have a rectangular signal. Trying to adjust THD using trimpot R9 and R4, at the output for SIN and TRIANGLE I have a square shape with rounded edges. The supply voltage is 12V. The XR is Chinese.
I can´t do remote diagnosis. In 99% of all cases it´s a soldering problem. Perhaps you have shorted out 2 pins or not correctly soldered another pin.
Forgive my ignorance as I'm new to electronics. I want to replace R4 with the suggested 500 ohm trim pot but am uncertain as to the routing of the pins. Trim pot with three, resistor location accepting 2. Do I put the first pin in hole 1 and then extend the wiper pin into hole 2, deleting the 3rd pin on trim pot?
Connect the wiper pin to one of the IC-pins, where R4 was connected.
Connect only one of the remainig two pins of the trimpot with the other IC-pin (the remaining trimpot-pin can be left unconnected).
The order of the IC-pins in connecting it with the trimpot doesn´t matter.
KainkaLabs Thank you for the fast response. You're a great teacher. I love watching your videos!
I wonder if it is worthwhile to redesign a new pcb with your modifications?
This is a great Video. I have one question regarding your second change (Swap R3/R5 from 5k1 to 1k): Both form a voltage divider with 1/2 Vcc output. Only the current changes (10k2 vs. 2k resistance in total). I don't understand this change. I would very apricate an explanation :)
The voltage divider R3/R5 has to be as low impedance so that the load through the amplitude potentiometer does not appreciably change the virtual ground voltage at the midpoint of R3 and R5.
Hi, which would you recommend, this fun-gen or the avr based one?
For my applications: definitively this one (with the modifications).
It has knobs for fast control of frequency & amplitude, is small, can be battery-powered etc.
In practice it is always more efficient/ergonomic to work with a "knob-controlled" device in contrast to a "pushbutton-controlled" device.
Very good info. How can I make a variable square wave out of my 2206? I need something in the 3Volt region.
What do you mean by "variable" square-wave? Variable amplitude?
@@KainkaLabs I should have said - variable amplitude. The fix Square-wave is too strong for testing my audio amp.
Hi. Can I just replace R2 for a multiturn pot with the same value?? the lowest value will be ok for 10 mV with this? I am working with audio.
There is an error in the Exar data sheet where it says that the output amplitude is 'inversely' proportional to the value of R3 where it is actually proportional to it (see figure 3). This is probably caused the amplitude pot reversal mistake by the PCB designer. Its function is to 'rob' the output pair of some bias and thus their gain. The manufacturers have also fixed the mounting screw issue by resizing and now use short screws and nuts as a PCB resting platform. As the XR-2206 was designed in the 70s, it is likely that its IP has been passed on so it shouldn't come as a surprise that the Chinese are now using it.
Yes. That´s why a picture (graph/diagam) tells more than a thousand words :-)
Hallo, Thank you so much for a very well explained and useful review.
I am trying to modify my function generator kit as per your recommendations but I am having difficulty in finding R2 (10 - 25K Ohm logarithmic potentiometer) having the same form-factor as the original R2 (to be replaced). In your video, I see that you did find one with the right form-factor.
May I request you to name the source and/or order number from where you procured your potentiometer, please?
I believe that you originate from Germany, I am also located in Germany. So if you could kindly provide me with the requested information that would be very helpful for me.
Many thanks in advance and best regards.
Nice video. I’m curious... What is the minimum input voltage required to produce a sine wave with 1.5V peak to peak? Thanks.
The minimum *supply-voltage* would be around 4...5 volt, I guess.
Roger, I have watched and enjoyed both of your videos about the XR-2206 Function Generator. Have fried my IC by inserting it upside down... I order new IC's (the old IC had markings scratched out). With your improvements and suggestions, I am considering making a board that takes your improvements into account and does not require use of modify parts or using SMD components. I was able to find on Amazon pots of the correct form factor in both 25k ohm & 1 Meg ohm. I will let you know when I have the new boards... and send you one if you like. Thanks again for you good work and analysis to make this a better tool for us hobbists.
Hi. That is a great idea. Would you be willing to make the PCB-files available for open source?
The potentiometers have a standard footprint and are originally from Alps.
@@KainkaLabs I Have the new board well underway... and have a photo of current configuration (dont think i can post it here ????. I have not yet decided whether to make it open-source or not... but will consider it.
By the way, In looking at the XR2206 data-sheet i see that the component values used in the board are what was in an example schematic in the sheet, and were not just pull out of the air. So, they might be ok without changing them if a genuine XR2206 is being used. If you would like a pic of my current version ... just send me an email at justjimjpc@gmail.com (Subject Line XR2206 Enhancement) Stay well and thanks for the reply.
That would be awesome!
Why not connect a high value resistor at the output to help discharge C10?
That´s a good idea. Haven´t thought about that.
Long ago, I had read that Exar had gone the way of the DoDo Bird. I was quite distraught because I loved their products, yet I didn't actually research it. Finding that they are still around really made my year. I was wondering though - are those ceramic caps or tantalum? If ceramic they could cause problems in such a circuit since the piezoelectric effect of ceramic makes them microphonic which could introduce noise into the circuit. Then again, I could be completely off base here.
In fact EXAR is still in existence but they don´t produce their old analog ICs anymore for a very long time now. en.wikipedia.org/wiki/Exar_Corporation
The frewuency determining cpacitors are in fact all ceramic ones (MLCC). They are of course microphonic and would never be used here in a precision circuit. But this purpose here to have a small, cheap, potentially battery-operated general-purpose function generator, it´s OK :-)
Hi Roger,
Is there an English version of your improved schematic documentation?
The schematics in the download link are in fact in English!
KainkaLabs Oh! Well I had it in German.
In fact, the link opens an unsecured webpage that my browser refuse to open. The only way was to go on the link you gave in another comment. ( www.ak-modul-bus.de/stat/funktionsgenerator_bausatz_xr2206_kit,pd0,,XR2206-KIT.html ) but only the German version is there.
@@NicleT - Roger made an error in the download link. He wrote www.kainkalabs.com/upload/index.php?f=15f605449521b3
but it's not https, so the CORRECT LINK IS:
www.kainkalabs.com/upload/index.php?f=15f605449521b3
Is it possible in XR2206 to adjust the amplitude on the form of a meander?
It would be helpful if you could post a picture of C9 & R2...but I do not think that you can do this on YT... unfortunately
I wish you would show how you switched the conetions on the amplitude mod zoomed in with c9 ???
Look at the schematic he showed on screen and work it out like i did. I should note though when lifting the centre leg on the new potentiometer for amplitude control you do not need to solder a wire from the centre pcb hole to the leg nearest the c4 capacitor as there is a track on the underside of pcb already there joining them. It's hard to see but i think in the video he soldered a wire bit don't think it's necessary
Thank-you!!!! When I first began learning electronics I came across a super simple circuit of two LED's in parallel but flipped in opposite directions. It called for applying an AC Sinewave which would alternate the flashing of each LED. My oscilloscope had a function generator BUT the sinewave's voltage output was so low it couldn't power on an LED. So I bought this same cheapo XR2206 but was once again disappointed in that it would only light one LED solid but the other LED stayed off. As per your suggestion, I added a 100uF Capacitor to the output AND NOW both LED's flash as expected and I can even adjust the frequency!! Can someone explain why adding the 100uF capacitor solved my issue??
Hi Roger, I can't work out how to rewire the amplitude potentiometer. The original schematic has left pin linked to R3/R5 and middle and right pins linked to 2206-3. Your schematic has left and middle pins linked to R3/R5 and right pin linked to 2206-3. So we need to remove middle pin from 2206-3 and link to R3/R5. But how to do that in practice? Isn't it hard wired in the PCB circuit? So I could solder a wire from middle pin to left pin, but how to disconnect middle pin from right pin/2206-3?
I have inteerupted the original PCB-traces and handwired the new connections to the potentiometer.
Another possibility is that you only solder the 2 sideways metal flaps, bend the potentiometer pins upward without any contact to the PCB and solder some wires directly to the pins with the right connections.
Only necessary if you use a logarithmic potentiometer (recommended) and want the direction of rotation to be intuitively right (clockwise = higher output level)
Thank you Roger.
@@KainkaLabs In my kit all of the potentiometers were 50K, so "Fine" and "Course" frequency controls functioned in an identical way. Changed course to 100K and Fine to 10K, but as I used 10-turn cermet presets, 100K course control is good enough.
What is your source for the 10K logarithmic potentiometers in this form factor? I built the circuit as you have shown and I suspect that the the 10K pots which I had on hand may be a problem. I have no amplitude control and I used an audio-taper potentiometer there at R2. My circuit is working for the square wave setting and I can adjust fine and coarse frequency very well, but I have no amplitude adjustment at all. However, when I switch to the sin/tri output I have no wave form whatsoever. I am very perplexed. I checked the entire circuit with an ohm-meter and all seems correct. I even swapped the IC and that is not the issue either. I have an unmodified board that works with the deficiencies which I have compared.
R2 is an ALPS type RK09K111 10KA. I got it from a German distributor but it is a standard type available from many sources/distributors.
Check the connections of R2 with a continuity tester, especially if there are no shorts between all 3 pins.
Remember for the log-functionality that you manually have to reroute the middle-pin.
If you have a scope, check the sine/triangle output directly at pin 2 of the XR2206.
This is a liniar potentiometer?! www.mouser.de/Search/Refine.aspx?Keyword=RK09K111.
I think this is the correct poti. RK09K113-LOG10K
@@KainkaLabs Do you mean RK09K113, which is for a vertical installation? RK09K111 is for a horizonal installation.
Thank you soooooo much
Great I just ordered that kit ,where can get the newer chip.
Ebay. Watch out for a genuine EXAR marking.
there is somewhere that we can buy it with the improvements? good job wek done
In our online-shop www.ak-modul-bus.de
The 10K pullup limits the current of the 10V square wave, but what can I do to also limit the voltage to 5V. Only having a 5V max sq wave makes things easier, as I won't have to jump from 10V to my regular 5V all the time.
You don´t have to limit the voltage.
All digital logic IC´s (exept the very first CMOS-series) can safely deal with overvoltages.
They have input protection diodes going to ground and Vcc which deflect overvoltages (or negative voltages) to Vcc and GND.
The only thing you have to limit is the current through these protection diodes.
Let´s presume the datasheet of your logic-series says that the max. current into any input is +/-10mA.
If you have a 10V signal into a 3.3V logic-input, then the minimum value of the input resistor (or pull-up of the XR2206) is:
R(min) = (10V - 3.3V)/10mA = 670 Ohms
That means that even a 1k resistor would be sufficient and a 10k resistor would be absolutely safe.
The other possibility would be to use a voltage divider.
A 10k/10k or 1k/1k-Divider would make a 5V square-wave output at the center-tap of the divider from a 10V square-wave input.
Can't find your updated schematics etc
Bruce Wood
Thank you for the very helpful video. Unfortunately I was not able top download your schematics. There seems to be an issue with the link. Can you please check, as I am really interested to try your suggested improvements. Thanks Georg Vietor
Our server is down ATM.
Try again next week.
You can also try to download the documentation from our shop:
www.ak-modul-bus.de/stat/funktionsgenerator_bausatz_xr2206_kit,pd0,,XR2206-KIT.html
("Dokumentation" --> "Deutsche Anleitung")
There you can already see the modified schematics on the first page
pause the video, and take a screen shot!
I connected 12v and got the polarity wrong way round. It fried the c1 capacitor and the xr2206 chip. I replaced the capacitor and chip and it's back up and running. I understand a diode between power barrel tip and positive on c1 capacitor and splice the original track on underside of pcb would offer protection against reverse polarity. Anybody know what would be the best diode with minimal voltage losses after input. Just noticed though that +vcc actually has more than one path through the circuit from power barrel it also goes to r3 and r5 voltage divider on amplitude section also so don't know how to pull it off
You can use any Schottky diode with let´s say >100mA current capability.
having a hard time finding a 1 mega ohm Potentiometer to replace the middle Fine Knob (R7) per suggestion on Kainkalabs schematic. the ones I find do not have 3 pins going down - they go to side. does anyone have a model number I could google. thanks
What is better XR2206 or ICL8038 as a generator? Are there any developments after the XR2206 or ICL8038 chips for the generator? What do you know about MAX038, is it better ?
One cannot say if XR2206 or ICL8038
The MAX038 was superior to all others chips before. I have made also a video about a Chinese MAX038-kit.
Today DDS-chips are way better than any of the above mentioned.
Hello. I just got my first multi meter and was doing voltage readings on the XR2206. and was wondering how come when I plug in 12v to the XR2206 it changes to 16v just going through the connector? is there a zener diode limiting it to 16v?
What? The XR2206 does not a charge-pump or something like that to generate higher voltages than the supply voltage. So you must be doing something wrong when you measure 16V with 12V input supply-voltage.
i probably shorted something together when i soldered it in school lol. Becaue I have 12v coming in but 16v after the connector.... so confusing@@KainkaLabs
Is it possible to adjust the amplitude of the meander (square signal) on this generator?
It´s an open collector output. So you can with a pullup-resistor get basically any output voltage.
Hi Roger!!
would there be a difference if a use non polarized capacitor for C10 AC coupling?
No.
The datasheet shows the output impedance of the sine/triangle output as 600R. Why not just add a 1K (or thereabouts) resistor between your new C10 and ground and stop worrying about the time it takes to charge C10? You can then pick a value for C10 to suit that resistor for the lowest frequency that you're interested in.
If you have the fine and coarse frequency adjustment pots in series, then the relative effect of the fine pot increases when the coarse pot is set to a low value. However, if you have the fine and coarse frequency adjustment pots in parallel, then the relative effect of the fine pot _decreases_ when the coarse pot is set to a low value. It's just swings-and-roundabouts and there's no "win" to be had - just a difference in preference.
Have you tried running this chip with a 10v positive and 10v negative input, rather than positive and ground.
That doens´t matter. The fake chip only works up to 12V total, no matter if you split the supply.
Cuanto es la frecuencia máxima? Esta bonito gran aporte
No hablo espanol. Pregunta in ingles, por favor.
FYI, as of 06/08/2022, Foxfire will not open the English link, even with the https/http correction.
How about using the 1k resistor, but add an attenuator on the square wave output.
That´s a good idea but adds another "complication" for beginners.
We finally settled on 3,3k resistor which is perhaps the best compromise between keeping the current into the protection diodes of digital ICs to a safe level and getting reasonably good edges with the square-signal.
thanks!!
Mine produces a cupped shape sine wave on the positive end. Almost like how a kid would draw ocean waves, sort of distorted and leaning toward the right. What would cause that?
does it do that only at maximum amplitude or also at smaller amplitudes?
@@KainkaLabs more pronounced at maximum amplitude AND lowest frequency. It looks like a piece-wise function of several exponential growth and decay curves tied together. Like desert sand dunes. Hard to explain, wish youtube had an attached imaged feature.
I also notice the jumper for the triangular function selection has no effect (whether plugged in or not, it displays the same).
@21:15. YES!! That's what I can work with. Thanks Roger.
I will let you know when I get my kit if the XR2206 is counterfeit.
The date didn't indicate a fake. What is the difference in logo.
If you show it in this video, please disregard.
I can probably google the logo. (?) :-)
The XR-2206 will be a fake. These chinese kits always use fake ICs. Exar Corporation was bought out a few years ago and the new owners discontinued various old products including the 2206, and Exar haven't made them for a long time.