Futurlec has them for $15.90
ICL8038 Precision Waveform Generator/VCO
http://www.futurlec.com/cgi-bin/search/search.cgi
But, they're only going to get more expensive.

But sure, the LM224N's would work fine for a low frequency signal generator. You can do a lot with them. There's a link I posted earlier on this thread to a schematic; you could modify that schematic to work with the LM224 - a one-IC multifunction signal generator. You won't run out of uses for a portable low-freq signal generator - even later on when you build or acquire a much better one, you can use your low-freq unit for modulation and other duties.

I built one that way about 8-9 years ago, but I used an LM348N (which is four LM741's in a single package) and put it in a small project box I got from Radio Shack. The circuit board was 1 5/8"x 1 7/8", the box is 3 1/4"x 2 1/8" x 1 1/8", fits in a shirt pocket. Powered it with a single 9v battery.

It's not fancy, has a freq range of 6Hz to 7Khz, 1.5v P-P output. I chose to keep the sig gen low-power to maximize battery life. You could use two 9V batteries for a +9 and -9 supply for more output voltage. Or 20 D-cells for +-15v, if you wanted that much exercise carrying it around

 

Here is an op amp function generator kit, but they also have a PDF with the schematic, parts list, and theory of operation. There are probably others. Google "op amp function generator".

 

Yes, the one that Ron H found looks like the exact same that I built; like I said, you can put it in a small project box.

Since it was low frequency, I used an RCA jack for an output, made up a cable with a couple of insulated alligator clips on it. I also used a 3-position slide switch to feed the board's output to the RCA jack. No, it doesn't have a very large output - but it's enough to drive a single TTL/CMOS input. If you need more, you can always run the output through an amplifier stage.

I don't know where my camera is at the moment - so I made a lousy attempt at scanning it just so you can have an idea on how it fit in the box. You can't see the pot for the freqency control at all, because it's out of the depth of field of the scanner; similarly so with the power switch and the waveform switch. But, it'll give you an idea for labeling your project, should you wish to package it compactly.

I made up the label using Microsoft Excel, and laminated it with clear plastic so it would last.

I also attached a ZIPped copy of the spreadsheet I made the label from.

If you don't have Microsoft Excel - no problem. You can go to openoffice.org and download a freeware compatible version.

 

I want to add a Variable voltage/frequency option to my power supply.

I read that a Multivibrater can do this. But I cant find a datasheet that explains the pins. I have a CD74HC221EE4 , SN74LV4046ANE4 (cmos logic w/voc) , HCF4098BEY also i have a UC252AN its a pulse width mod?.

Which would be the best for a Variable voltage/frequency power supply.

There is a *huge* difference between a power supply and a signal generator. One gives out power, the other gives you signals with practically no power. You asked about "power supply" and the responses are about signal generators. Maybe you meant signal generator but you all need to make sure you're all on the same page.

 

He wants a signal generator. Please read the whole thread before replying.

 

Also I just received a LT1057
its a Precision High Speed Op Amp. Can i use that to get higher frequencies?

 

Also I just received a LT1057
its a Precision High Speed Op Amp. Can i use that to get higher frequencies?

You generally can't make a high-speed function generator with just op amps, because one of them is used as a comparator, and op amps make poor high speed comparators. If you use op amps where they are appropriate, and true comparators where they are appropriate, you can make a fairly high speed function generator. The MAX038 was the best function generator IC, at least from a speed standpoint, but it was discontinued, probably because digital techniques have surpassed it.
BTW, LT1057 looks like a nice op amp, but in the universe of op amps, it isn't high speed.

 

But an opanp has both inverting and noninverting parts. which do i use where?

 

The best introductory guide to Op Amps in the whole universe can be found here: http://www.allaboutcircuits.com/vol_3/chpt_8/index.html

 

Sorry about the Nte864. The price has increased by about 6X since I last got some about 6 months ago. Good thing I designed away from the critters.

 

I still dont get why they stoped making them. and which part inverting or non inverting do i use where. I looked thought that awesome guide but i did not find it.

I tried to do this one but it would not blink my led.

all so whats the difference if you connect a pot differently. (see pic)

whoops i forgot to add the pic.

 

b.ring
u.p
m.y
p.ost

so whats the difference between the two pots?

 

You hook to the inverting input if you want to invert, or don't mind inverting. You hook to the non-inverting input if you don't want to invert.



There is no difference in function between the two potentiometer configurations.

 

oh ok. thank you.