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I'm trying to design an input circuit for a microcontroller that will work with 1-10 V dimmers. There appear to be two standards for dimmers, current source and current sink, and I'm trying to work out if I can create a system that will work with both.

As I understand it, most domestic lighting uses current sink dimmers: the controller or ballast provides the current with a 10 V or more signal and the dimmer reduces that signal.

There is also a standard from theatrical lighting, where the dimmer provides the voltage and current and the controller just measures the voltage level.

I've designed my circuit as a current source using an LM334 plus a Zener diode to turn the supply voltage of 12-14 V into a current source that will float up to 11 V. A potential divider, crude low pass filter and 3.3 V Zener diode convert the signal into 0-3.3 V for an analogue to digital converter.

First question. Did I do anything wrong here or is this workable? It seemed OK when I breadboarded it.

Second question. It would be great if this worked or automatically adapted to the two different standards. Can this circuit be adapted to work with a 0-10 V current source input signal?

enter image description here

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  • \$\begingroup\$ See if my explanation on Dimmable mains PSU control helps. \$\endgroup\$ – Transistor Jul 13 at 8:48
  • \$\begingroup\$ I’m not seeing how the LM334 is measuring current - didn’t you say you wanted to do that? At any rate I’ve used the LT6105. It works in high and low-side sensing and can run on supplies from ~3V to 36V. Its output range can be matched to your ADC with one resistor. Link: analog.com/media/en/technical-documentation/data-sheets/… \$\endgroup\$ – hacktastical Jul 13 at 17:56
  • \$\begingroup\$ The LM344 isn't measuring current. The circuit as it stands is just a current source with level shifting down to 3.3v. The LT6105 is quite an expensive addition to the circuit so its not an option for the project I'm working on. \$\endgroup\$ – Tudor Jul 14 at 7:59

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