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I'm trying to build a circuit which allows an Arduino to control 6 channels of lighting from an old Strand Act 6 Dimmer.

These dimmers have 8-pin DIN connector on them like this specification. Pin 7 is +10V, Pin 8 is GND, and Pins 1-6 control the dimmers on channels 1-6. This is so that a variable resistor can be connected from GND to +10V, with its output going to one of the channels (so no powered controller is needed). However, I'd like to control 6 "variable resistors" from my Arduino using PWM.

I'm following this guide. My Arduino outputs PWM on 6 pins, each of which goes through its own filter circuit:

http://www.hoelscher-hi.de/hendrik/light/demux/demux.gif

which produces a voltage between 0 and 10v at OUT. My question is: this 0-10V is relative to the Arduino's GND and +12V input power. Will simply connecting the OUT of each filter circuit and GND to the corresponding pin on the DIN connector work, or do I have to somehow make the 0-10V OUT correspond to the +10V/GND coming from the dimmer?

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You should be fine connecting the signals directly, with GND tied to the DIN GND pin. You do not need to connect at all to the +10V coming from the dimmer.

The 12V supply (if regulated) should be okay to power the LM324.

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  • \$\begingroup\$ Why is it not necessary to connect the +10V coming from the dimmer? I see how a voltage can be applied between the LM324 and the DIN GND, but I imagine the circuitry needed to read that voltage measures the drop from the DIN +10V to DIN GND. Is that completely wrong? \$\endgroup\$ – par Aug 24 '17 at 7:06
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    \$\begingroup\$ @par It would simply measure the voltage relative to DIN GND. The 10V is there in case you have something like a pot which needs an external supply. In this case OP has a 12V supply. The LM324 can just get to 10V reliably at the output with a 12V supply. \$\endgroup\$ – Spehro Pefhany Aug 24 '17 at 10:37

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