What to do with an old project?  (which uses an XR2206) - Page 1
Forum section: electronics / general

author: Brumby
author_rank: Unknown
timestamp: November 25, 2018, 01:58:02 am
content: Rummaging through the garage for something else, I found an old project that was built up but never finished off. Housed in an unmarked jiffy box was a completed "Soundbender" kit - ETI 492.While I have no interest in resurrecting it, it would seem a shame to toss it. The PCB is a piece of single sided fibreglass board I got for cheap. Tracks were laid out using a Dalo pen and etched at home. The result wasn't pretty, but it worked.The only bit of interest is that it has a genuine XR2206 of 1981 vintage which has been socketed. A prime candidate for redeployment. It has a cheap 741 op amp which is so cheap, it only has the marking "741" on it and another chip which doesn't even have that - and I'd have to go to the circuit to find out what it is.So - what to do with the XR2206? I was thinking of a signal generator - but I'm happy to take suggestions...

author: vinito
author_rank: Contributor
timestamp: November 25, 2018, 02:10:59 am
content: The picture might be better than your eyes. Looks to me like it reads 741 also.

author: Brumby
author_rank: Unknown
timestamp: November 25, 2018, 02:30:43 am
content: You are right. I didn't look that closely before. Reviewing the image indicated it was, but pulling out the head magnifier and getting it into the right light showed it was another 741.But I'm not fussed about either of those.

author: wilfred
author_rank: Super Contributor
timestamp: November 25, 2018, 03:43:31 am
content: It is from ETI Feb 1982 for those who want to look it up. The magazine didn't seem to know the Cylons aren't from Star Trek.https://www.americanradiohistory.com/Archive-Electronics-Today/Australia/80s/ETI%201982-02%20February.pdf

author: cdev
author_rank: Super Contributor
timestamp: November 25, 2018, 03:49:15 am
content: I would make an analog siggen. That is still a useful chip.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 25, 2018, 07:36:22 am
content: Quote from: wilfred on November 25, 2018, 03:43:31 amI never really saw the need for it.I can do an excellent Dalek, & a creditable Cylon without the need for any electronic devices .

author: Messtechniker
author_rank: Frequent Contributor
timestamp: November 25, 2018, 08:21:10 am
content: Well, mine are at home here together with some of the other oldies

author: Brumby
author_rank: Unknown
timestamp: November 25, 2018, 08:44:57 am
content: Quote from: cdev on November 25, 2018, 03:49:15 amThat's top of my (very short) list. Anyone have a circuit they can recommend?

author: cdev
author_rank: Super Contributor
timestamp: November 25, 2018, 11:59:16 am
content: I may have one somewhere. But I would just Google for it. Also, if you go on ebay, there are many sellers still selling XR2206 siggens.Maybe you can extract enough info there to find or make a schematic?Maybe I can find one.Watch out for fake XR2206 chips on ebay!See

author: nugglix
author_rank: Regular Contributor
timestamp: November 25, 2018, 01:03:51 pm
content: Quote from: Brumby on November 25, 2018, 08:44:57 amYou might want to have a look at:fromhttps://www.youtube.com/channel/UCDqryeq1kMDSEQwltWqASrA/videosHe "recently" even started a new siggen project.

author: rdl
author_rank: Super Contributor
timestamp: November 25, 2018, 02:24:08 pm
content: Quote from: Brumby on November 25, 2018, 08:44:57 am

author: Messtechniker
author_rank: Frequent Contributor
timestamp: November 25, 2018, 08:27:52 pm
content: If I remember correctly, Elektor carried a XR2206 circuit capable of doing a 1:100020 to 20 kHz sweep. I.e. much better and more useful compared to the data sheet circuit.

author: Brumby
author_rank: Unknown
timestamp: November 26, 2018, 12:01:33 am
content: Quote from: Messtechniker on November 25, 2018, 08:27:52 pmNow that's something which piques my interest.

author: lowimpedance
author_rank: Super Contributor
timestamp: November 26, 2018, 12:35:52 am
content: The December 1984 issue is the one , and its a 1:100 VCO (0.1V to 10V) with a freq. range of 1Hz to 110kHz. It used a double sided PCB.

author: rdl
author_rank: Super Contributor
timestamp: November 26, 2018, 02:09:01 am
content: I remember trying to find a copy of that Elektor article or schematic years ago without any luck. Times have changed.https://americanradiohistory.com/UK/Elektor/80s/Elektor-1984-12.pdf

author: lowimpedance
author_rank: Super Contributor
timestamp: November 26, 2018, 02:38:41 am
content: Indeed , that's a most excellent site.I also actually have the 1984 mag. too , but having recently discovered that site the piles of dusty old mags are looking more recyclable every day. Particularly when I need space for the latest bit ofjunkfine kit that I have acquired.

author: Brumby
author_rank: Unknown
timestamp: November 26, 2018, 02:51:36 am
content: Found it here:https://archive.org/stream/ElektorMagazine/Elektor%5Bnonlinear.ir%5D%201985-01#page/n13/mode/2up... with DC offset adjustment, no less.

author: Brumby
author_rank: Unknown
timestamp: November 26, 2018, 03:48:27 am
content: The idea of matrix board/Veroboard and the like don't seem the best if I want to keep things tight, so the sensible approach would be to use the PCB they've designed. So now it's just a matter of getting one.- Do I try a home job?- Do I use this as my first foray into getting a PCB made? This would involve creating the files from scratch - and all I have at the moment is Kicad.- Do I try Elektor (or someone else) for a premade board? (Would they still be available?)

author: duak
author_rank: Super Contributor
timestamp: November 26, 2018, 06:07:19 am
content: I remember that the XR2206 chip did two things that the 8038 couldn't:1.) the AM modulation input allowed you to build a simple tone burst generator. That is, with some sort of timer or counter, you could have it generate a number of cycles at one amplitude and then a number of cycles at a different amplitude (or off). I've never needed one, but it's apparently good for speaker testing.2.) the VCO is an emitter coupled astable multivibrator. (sounds just a bit kinky, no?) The waveforms at either end of the timing capacitors are positive or negative ramps interleaved with a fixed voltage. If you take the difference of these two waveforms, you get a triangle wave. They're probably just dandy for generating a cross on an X-Y display. (I think I did that when I was a young lad.)Cheers,

author: GK
author_rank: Super Contributor
timestamp: November 26, 2018, 12:13:43 pm
content: Quote from: vk6zgo on November 25, 2018, 07:36:22 amThink you could compete with this guy?http://youtu.be/tpUtUQ5YC-Q

author: lowimpedance
author_rank: Super Contributor
timestamp: November 28, 2018, 03:02:25 am
content: Quote from: Brumby on November 26, 2018, 12:01:33 amThere is also a companion project for a sweep generator, see the November issue 1985.All jellybean stuff too, although they used a double sided PCB like the XR2206 gen design.