Analog: Relays, Machine Unit (publ. 2025-03-21)

I wired up another integrator module, this time using a TG2 5V relay, to switch between IC and OP mode. Using relays, I can have all the integrators driven by one switch. My original idea was to use solid state relays but the TG2 relays are already on hand. I'm only using +/- 15V rails right now, so I just used resistors to bring the current down to the nominal coil voltage for the TG2 5V relay, taking into account the coil resistance.

The Grappendorf schematics for the voltage reference module provide a +/- 1V reference output. However, the project examples he gives show him using +/- 10V, which makes a lot more sense. My understanding is that 10V was a common machine unit for analog computers, and also noise is more pronounced at just 1V. So I replaced the R3 resistor, which is the feedback for the first op amp, to be 100k instead of 10k, which bumped the gain up to -10, providing +/- 10V on the module outputs.

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