and the following set of numbers did not work with this set up.
I tried ordering more chips with the correct numbers based on the picture of the chips on ebay and they sent different chips that didn't work. I'm really annoyed with the 8038 chip situation. So, I'm going to revisit this LFO project with a different circuit, one that doesn't utilize the 8038.
For my modular project, I'm trying to keep it simple, at least in the beginning, so i can learn what I can from each circuit I build. A simple LFO circuit, is something I've tried to build a few times, with limited success. It wasn't until I was clicking around on YUSYNTH (my new favorite website. It's loaded with projects and information), that I came across this ultra simple implementation of the ICL8038 chip.
I wired up the circuit almost exactly how it is here and it worked pretty good, But I didn't have the necessary switch for all the cap and resistor combinations--which led me to experiment with different combinations of resistors and caps to cover the range I wanted. I put in a 1uF Tantalum cap at pin 10 and a 1M pot (replacing R5, R6, & R7) and was able to achieve the ultra low oscillations I was looking for. The 1M Pot basically working as a Coarse tune, and the 10K pot working as a Fine tune. I also found that the voltage input was basically useless to me, it seemed to hardly affect the frequency and when i hit it with higher voltages, it would stop oscillating altogether. I decided to skip that aspect of it, at this time anyway.
Theres some extra chips on there because I was testing to see if the square wave output would work as a clock for the a 4017 decade counter chip. it does.
Above is the schematic that I came up with and ultimately built into a module.
Electronics is one of those things, where I don't exactly understand, at what point you can call a circuit "my circuit". I mean, how much do you need to change and does it really matter if you're giving away the plans for free. Anyway, I felt like I changed enough to call it my circuit, but it's really just a modified version of the circuit I found on Yusynth.... It's like a remix
I decided to just draw the PCB.
I made a little mock up of the traces
I thought it might be easier, especially with the chip, to drill the holes first, using a perf prototyping board to set the spacing. I guess that helped, though drawing little traces with a fat tipped permanent marker can be kinda stressful.
I realized, after I started etching the pcb, that I forgot to put the transistor rate indicator on there, so I added that. Strangely, I found that drawing on the partially acid etched board was easier, and the ink stuck to it better, probably because the acid made the surface less smooth. It made me consider dipping my boards in acid for a second before I apply transfers to them also. who knows?
The board came out good and so i put the components in there.
In the end, I opted for a switch between Sine and Triangle waves. The square wave gets it's own output, so I can use it as a clock.
so, I spent some time this weekend and made a PCB in photoshop which everyone is welcome to use. let me know if there are any problems with it, because, I hand drew mine. It's designed to be transfered, so you should be able to read the writing correctly after it's transfered.
In the video, I have the 8038 LFO hooked up to the cut off frequency of my Synthesizers.com State Variable Filter. Enjoy.