I need to make up an adjustable 1 to 200 Hz square wave signal generator, current sink output, to test a PLC I'm having some issues with. The system is 24 volt DC. Any ideas where to look for a circuit would be much appreciated.
Thanks for your time
Grep for XR-2206 circuits on the web. You need 3 decades to cover from 1 to 200Hz, and this chip will do five. It needs several hand-fulls of resistors and capacitors for full functionality, but you may not need it all. Jameco Electronics sells just the chip for $3.59 and also a basic function generator in kit form for $25:
You specified the system voltage but not what your square wave output amplitude must be. You'd also have to elaborate about your current sink requirement.
And finally, you'll need to drop the 24V to 12V if you build the kit, which is easy to do with an LM78L12 voltage regulator and a couple of caps. The above circuit draws only 15mA. The chip, however, can tolerate a 26V supply.
Here's another one for you, not as fancy as the Jameco
thing but it should work equally well. If the logical zero isn't
low enough you can always add a transistor or a fet to
drive the plc.