Signal Generator

[italianguy63]

Does anybody have a hint, link to a cheap and easy signal generator?

I have a probe, and it shows where signal may drop out.  But figured it would be good to inject a signal around that point to see if the downstream portions work...  Before I go treasure-hunting, de-soldering everything.   

MC

[GibsonGM]

There are a couple of very easy ways to do this, Mark.  You can just line out a stereo or phone, and use that to play a song as your input to simulate your 'guitar'.  Or, use a 555 oscillator to do the same. Square wave will be more like distortion, tho.    There are many free sine generator software programs ("visual analyser" for one), so you can line out from your computer to the circuit.  I like that one as you can select shape, frequency, sweep, etc. 

For more advanced work, you would need to build a better sine wave generator - there are a few out there, including a great one that merlin b put together, on his site (search "valve wizard", it's right on his site).


Might try to figure out about what level the signal actually IS where it drops out, so you can mimic the level correctly!  Good luck. 

[merlinb]

http://www.diystompboxes.com/smfforum/index.php?topic=83930.40

http://valvewizard.co.uk/siggen.html

[bt2513]

I use a synthesizer/keyboard with a key pressed.

[lars-musik]

Have a look at that little circuit/stripboard: http://www.paulinthelab.com/2012/12/signal-injector-tracer-stripboard.html

Very handy. Take your time to browse paul's blog if you didn't know it before. You'll find a lot of useful/funny/essential things: http://www.paulinthelab.com/


Edit: I forgot I made a pcb layout for that signal injector.http://i1244.photobucket.com/albums/gg578/lars-musik/Musikkram/Sig_In_paul.png

[slacker]

The device you're using to ask the question is a signal generator

[Seljer]

I've got this one built and boxed up: http://www.geofex.com/FX_images/q&dosc.pdf
For the buffer I used a PNP instead of an NPN so it biases higher and has more headroom. I didn't add the diodes but the 50ohm trimmer is a neccesary addition if you want to get a really clean sinewave without any harmonics. I also just put a 10k volume pot on the output to set the level.

[orangepit]

This one is pretty sweet. It's a little bit more complex but it sweeps from about 30ish Hz up to 18ish kHz with the turn of a pot. Level is adjustable too.
http://sound.westhost.com/project86.htm

I just finished up a single sided pcb for it tonight. The original I made I accidentally designed it around an op amp with the - and + inputs swapped. Oops! Very careful IC leg maneuvering fixed it but I wanted to redesign the pcb anyway.
If anybody is interested I will make a parts layout for easy populating.

[GoranP]

sure!
do you have any boards for sale or maybe willing to share the gerbers for a bit of monetary compensation?

[karbomusic]

This little fella has an AWG and I think it is the coolest thing eva for 54 bucks. I'm dying to put one in a pedal!

https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2205907_-1

[orangepit]

No gerbers and I etch myself so no spare boards. I can give you the eagle files if you want to tweak them, but the designer from the link I provided sells a dual layer pcb that is slightly smaller than mine.

Here is the layout. The output goes to an off board 5k log [level] pot to ground with the wiper to the output jack. Use an off board power switch or use a level pot with a built in switch if you don't like the level to stay in the same place.
For the diodes, I twisted two 1n4148s in series and clipped off the excess twist and soldered it to create a single part. DON'T use a single diode on the pcb! Refer to schematic.

[GoranP]

yeah, thanks, eagle files would do just fine!

[rring]

If you can program a PIC you can build this with about 6 parts. By adding a couple of switches you can produce square, sine or any other waveform.
http://circuitsalad.com/2014/06/10/dds-audio-generator-made-from-pic-microcontroller/

[italianguy63]

I picked up a Velleman MK105 kit.  Has anybody played with one of these?  If so, does anybody know a simple mod. to vary the frequency?

MC

[orangepit]

Here you go GoranP, these are my eagle files.
https://dl.dropbox.com/s/32hwybjqz8juqzl/MiOsc%20by%20orangepit.rar

[italianguy63]

I put together the MK105, and put it in an enclosure.  Added external pot for gain, and a 1P4T for changing between the waveforms.  Used a TS jack for output, and an old Harbor Freight DMM lead for a probe.  Came out and works great!!  I'll post a pic eventually, but my computer got hit with a power surge last night.  It blew up the motherboard.  I have 4 caps on the board that are swollen... Seems the P/S is still good.  More work in my future...   

On the bright side.  Leave for the "Loudest Boat in the World" tonight.      See you guys in a week.

[GoranP]

thanks man!
im on vacation right now but will take a look in a week when I get back.

[EATyourGuitar]

oshpark has a minimum order of 3 pcb's so I have two of these leftover that I don't need. I think I paid $2 each if anyone wants to save them from the landfill. sine wave is very low distortion. and you can switch to tri or square.

[orangepit]

That's nice and small with great features like triangle and sweep. I like it. Those boards will get snatched up quick. It has some downsides though.
I built the one I did for a few reasons. It's easily powered by a [dead!] 9v battery, making it portable. It is useable down to 6.3v and only pulls 1.7mA for sine. It also has much lower distortion.
I highly recommend people learn to etch their own pcbs. It is very simple once you have a few under your belt. You can't beat soldering components an hour after designing the layout!

[EATyourGuitar]

no sweep here on my pcb. I used 100kb + 10kb + 68nf for 140Hz to 14Khz however I checked the datasheet and you can probably use 250kb + 10kb + 100nf to get the full 80Hz to 20KHz range. if you over shoot your 20KHz just put a 470k resistor across your 250kb pot.

I like your design for the low cost and no obsolete parts. obviously my pcb is smaller and quicker to build that is the tradeoff.