Tuesday, February 1, 2011

Square Wave & PWM Board - Nearly Done

Here's the board with most of the components added.
Just waiting for some PCB mount switches and a 2SC2878 transistor to arrive in the post, and have to find some monotron-like knobs - PCB mount type.

Design from Takeda's Monotron++ at beatnic.jp
Also in the process of finding out if a NE5532 can substitute a 4580 op amp. It seems that some people think a 5532 will only operate properly at over 9V, and requires +/-V supply. The 4580 can run as low as 3V, so 5V Vcc will work. The 5532 is rated as low as 2V (in spec sheet) but may require +/-V supply.
This should be OK as I've made another circuit to "mix" the VCO outputs from 2 monotrons (more on this later...) for which I had to get -5V for an LM358 op amp to run properly. It seems most people go for a +/-12V supply for such op amps, but that is just from uneducated and uninformed research (i.e., on the web). Again, this chip is rated quite low, so hopefully it'll make it with +/-5V supply.
I'm getting -5V from an ICL7660, which I think replaces (or is identical to) the MAX1044. By hooking up some capacitors and grounds, you can invert your supply voltage. The circuits I found (which were identical) worked for both 9V and 5V supplies. In fact, the circuit (which I'll post later) states on the schematic that it is good for 3.5V to 10V; that is, you can get -3.5V to -10V from a positive supply.
More progress reports to follow.

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