Good Little Signal Generator

[WLS]

Hi Everyone,

Recently picked up a first time scope off eBay and through the help of the good people on this form I don't think I did too bad. It's a three channel scope 100 MHz with dual trace, tons of other features and appears to be working fine all for $120.00 at the door step!

Thanks for the help!!!

Anyways to keep on the topic of this thread after getting the scope, now it is time for a decent signal generator. I was looking at some circuits here in the forum and other places on line. And even-though they are not real hard to build I am finding that to get an assortment of different signals will require a couple different circuits.

Again, I find myself on eBay looking as to the price of a signal generator and found them to be astronomical in price for the most part and anything that I would consider with out going into some tube driven generator that was in someones attic for what appears to be a hundred years was going to cost me close to a bill and a half.


Then I came across a software driven signal generator from a company called Virtins Technology that turns your PDA into a signal generator.

Here is the link http://www.virtins.com/page3.html.

I checked out on my scope with the two day trial period they offer and found it to be a very reasonable product. But I was wondering if anyone else here has used this product and what you think about it?



Bill

[waltk]

I was looking at some circuits here in the forum and other places on line. And even-though they are not real hard to build I am finding that to get an assortment of different signals will require a couple different circuits.

Is the XR2206 one that you considered?.  It lets you generate sine, triangle, and square waves, and even adjust the symetry.  I don't whether you were looking for more than this, but if you are interested, I can share a PCB layout with all the adjustments listed in the datasheet.

[brett]

Hi
if you just want square, triangle and sine waves, you can make these easily youself with a DIY generator. 
I have a schematic somewhere of the one that I use (based on an LM13700) .  It was published in either Silicon Chip or Electronic Australia.
Jaycar (here in Oz) used to sell it as a kit for about $40 (US$30).  If I recall ok, the frequency range was 1Hz to 100kHz, and amplitude from 0.01 V to 10V.
cheers
PS a very simple one can be made from a CD4049 and a few simple components. 
Set up a couple of inverters as a square wave generator, another as an integrator (to get a triangle), and another as a clipper (with feedback diodes, to get a sine wave).

Like this:
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=9588&g2_serialNumber=2
Varying the fedback capacitor or resistors changes the frequency.

cheers

[WLS]

waltk,

I was just checking out the  XR2206 on moushers site and the chip offers everthing that I would be looking for in a signal generator. If you would be willing to share your schematic and pcb template I would appriciate it.

This would save me a great deal of time.

Thanks

Bill

[waltk]

The schematic is almost directly from the datasheet.  I just recently made a couple of these using this layout (or one very close to it) that I drew myself.



Here's a picture of a prototype that I used for testing.  You can see that I use three-pin connectors for pots and jacks, and I socketed the trimpots (so I can just replace them with a resistor when I don't really to make them adjustable).  The white wires are for switches - an SPDT that switches between square wave and sine/triangle wave mode, and an SPST that switches between sine and triangle (look at the datasheet to see why this is neccessary).  One peculiar thing I noticed was that the output level pot did not seem to do anything when it puts out square waves - the output was always maxed at about 6V.  Of course that might have been caused a mistake in design or execution (by me).



I put the etchable PCB layout in my gallery, but I might have an extra PCB laying around that I could give you.

[solderman]

waltk,

I was just checking out the  XR2206 on moushers site and the chip offers everthing that I would be looking for in a signal generator. If you would be willing to share your schematic and pcb template I would appriciate it.

This would save me a great deal of time.

Thanks

Bill

Hi
I have bean looking for someting like this as well. Did a littel googling and found this http://www.nuxie1.com/guides/fungen-v2-kit-2.html It should be pretty easy to convert this schematics to a PCB although if some one has it ready it wold be appreciated. The info about the circut is very good with scope pics from different wave forms and such.

\\Solderman

[waltk]

An update... I just noticed something about the test board in the photo - it was from an earlier layout that I had forgotten to put in the 10uF cap in.

[solderman]

The schematic is almost directly from the datasheet.  I just recently made a couple of these using this layout (or one very close to it) that I drew myself.

[

I put the etchable PCB layout in my gallery, but I might have an extra PCB laying around that I could give you.

That was fast
Whats the difference/ extras between yours and  the one i found on the net. is there worth the effort to create a PCB layout for the schematics or is this one good enoughe???

//Solderman

[waltk]

I have bean looking for someting like this as well. Did a littel googling and found this http://www.nuxie1.com/guides/fungen-v2-kit-2.html It should be pretty easy to convert this schematics to a PCB although if some one has it ready it wold be appreciated. The info about the circut is very good with scope pics from different wave forms and such.

Thanks for the link.  That's an interesting looking design - a little fancier than what I had.

[waltk]

Whats the difference/ extras between yours and  the one i found on the net. is there worth the effort to create a PCB layout for the schematics or is this one good enoughe???

It has some extra buffering on the square wave output, and an extra voltage regulator in the power supply to support it.  It also has a "virtual ground" piece - I don't really get why that was necessary, but I'm no design genius.  The frequency adjustment seems a bit more complicated than it needs to be - perhaps to better support a wider frequency range.  I was only interested in audio frequencies, so I stuck with the simpler scenario in the datasheet.

[solderman]

Whats the difference/ extras between yours and  the one i found on the net. is there worth the effort to create a PCB layout for the schematics or is this one good enoughe???

It has some extra buffering on the square wave output, and an extra voltage regulator in the power supply to support it.  It also has a "virtual ground" piece - I don't really get why that was necessary, but I'm no design genius.  The frequency adjustment seems a bit more complicated than it needs to be - perhaps to better support a wider frequency range.  I was only interested in audio frequencies, so I stuck with the simpler scenario in the datasheet.

Hi
Thanks
Seems that yours is Good enough then
//Solderman

[WLS]

Thanks Walt for the layout, I'll order the parts on Monday. 

If you do have an extra PCB laying around let me know what I need to send you at least enough to cover your cost. Since I just was getting started into doing my own PCB infact I was going to do some test pieces tomarrow to get my exposure times correct before doing my 18 volt Deluxe Electric Mistress.

The PCB Template from GGG's sight is tight and needed some cleaning up this seams to be the case with all his layouts. As my friend Solderman so graciously pointed out to me in a previous thread on his experience with a PT-80.

Your signal generator looks excellent and put the rest I've seen to shame.

I can hardly wait to start on it!

Thanks Again!

Bill

[waltk]

Hi Bill,

Just PM me with your mailing address, and I'll drop a pcb in the mail for you (no charge - all it takes is a stamp).  To match the data sheet, you'll have to use a 10uF cap between +9V and GND off-board.  Also, if you want to try the PCB I send, I highly recommend socketing the XR2206 (so you can reuse it in a different board if you decide to).  It's a sixteen-pin chip, and I just used two end-to-end 8-pin DIP sockets (because that's what I had).

Since I just was getting started into doing my own PCB...

Good luck with your etching.  BTW, do you have a drill press, and something to cut the PCB material with?  After the etching is done, it can be tedious to drill the holes without a drill press.

-Walt

[waltk]

To match the data sheet, you'll have to use a 10uF cap between +9V and GND

I mis-spoke about this.  The 10uF cap goes from the wiper of the output level pot to ground - that IS on this version of the layout.  The missing cap is a 1uF cap  between +9V and GND (from the datasheet).

I have a confession to make... I also just bought my first o-scope on Ebay (hasn't even been delivered yet).  I finally decided to get one because I'm interested in seeing the output from this circuit (among other things). 

I've been working on a complete effect "debugger" circuit that includes this oscillator, two independent power supplies (LM317-based - one 12-volt, one 9-volt/adjustable with 4 outputs), two independent amplifiers (based on TBA820Ms - one dedicated to an audio probe, and another to monitor the effect output), and dual IC-based buffers that I can insert where needed in the signal chain.  I plan to put it in a box with a speaker or two to reduce the rats nest of wires that I usually have on my workbench when testing/debugging.  Right now, I actually have a completely populated PCB with all these things on it (3.1 X 3.4 inches).  When I get time for a little more testing and tweeking, I'll put my results out there for anyone who wants their own.

[newperson]

i am not seeing your name in the layout gallery can you point me to it?

[waltk]

i am not seeing your name in the layout gallery can you point me to it?

Here: http://www.aronnelson.com/gallery/main.php/v/waltk/XR2206Oscillator/

[newperson]

thank you.  searching "waltk" would not work for me.

[WLS]

Hi Bill,

Just PM me with your mailing address, and I'll drop a pcb in the mail for you (no charge - all it takes is a stamp).  To match the data sheet, you'll have to use a 10uF cap between +9V and GND off-board.  Also, if you want to try the PCB I send, I highly recommend socketing the XR2206 (so you can reuse it in a different board if you decide to).  It's a sixteen-pin chip, and I just used two end-to-end 8-pin DIP sockets (because that's what I had).

Since I just was getting started into doing my own PCB...

Good luck with your etching.  BTW, do you have a drill press, and something to cut the PCB material with?  After the etching is done, it can be tedious to drill the holes without a drill press.

-Walt

I just about have everthing for the layout except for the IC laying around which I'll order on monday along with some other stuff to justify shipping.

I am starting to have quite a collection  of parts. Every time I place an order I try to anticipate what I would need to build something different. Most of the times I just breadboarded the project to see if I like it.

You'll love having a scope I like you am very curious as to what exactly is going on with the signal. And a scope just adds another dimension to building circuits and understanding what is causing the changes...

I am still fairly new at this, but what can I say besides I am hooked.

As far as a press I have an older dremel model 395 and recently pick up a gently used 212 press. It was sticking a little but I shot some lithium in the gear box and everything works nice and smooth now. I can't see how any one could do it with out a press and still have drill bits when they're done.

To cut my board I am using dremel's e-z lock diamond saw blade for cutting ceramic tile. The blade is thin and when using it last night for the first time. It cut through the board with only generating a little bit of dust and causing very little waste on the boards edge.

Your complete effect "debugger" circuit sounds like a pretty intense project. I am presently working on building an Electric Mistress using GGG's PCB template that I had modified a tad. I am going to use a tc1044 to crank the voltage up. Instead of using the eighteen volt transformer. I will be using five 220uf polarized caps in the pedal. Two to get the charge pump up to 17(+) and the other three as to his schematic. I breadboarded the power supply mimicking my PCB layout and ended up that the circuit gets 26(+) volts. For the 15 volt regulator I went with a 220 package since it has the heat sink. I also added an extra trace to accommodate a resistor since I am going to put in a external pot for the clock instead of the trim pot. I read that it really opens up a world of sounds. I did read though that when the pot is turned to much in one direction you'll start to hear ticks. So I added the resistor to allow the clock voltage not to exceed that point.


Anyways Walt I can't thank you enough for the board and the layout. I will use sockets for the IC as you sugessted.

Thanks ,

Bill