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I have an El-Driver that has a potentiometer to control the brightness.

I would like to control the brightness with an Arduino, replacing the potentiometer.

Here is the schematic of the brightness control stage:

schematic

simulate this circuit – Schematic created using CircuitLab

I tried to replace the potentiometer with a low pass filter connected to a pwm pin on the Arduino but it didn't work.

Can someone direct me in the right direction?

xoxu
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1 Answers1

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I assume you are reverse-engineering the circuit? Without a full schematic, it's hard to figure out an elegant solution.

I also assume that the subcircuit you show is a low-voltage control signal. If it is low-voltage, you could just use a digital potentiometer.

There are many styles of digital pots. They can be controlled by logic, serial (SPI or I2C), etc. They come in different packages, with different resistance ranges and resolutions.

As an example, please see Microchip's MCP4017. They can be found for around $0.50 USD in single quantities:

mcp4017

bitsmack
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  • Yes, digital potentiometer ICs are indeed a thing, but— The operating voltage of EL wire is around 100VAC, and these potentiometers are only good to whatever their Vcc is, 7VDC max. Assuming the resistances pictured in the original circuit are correct, you'd still see over 80V over the potentiometer. I'm afraid that wouldn't work for very long. – Richard the Spacecat Aug 06 '19 at 06:44
  • @RichardtheSpacecat I don't think the circuit in the OP's diagram is actually exposed to the high-voltage output. If it was, the resistor divider transistor combo would't modulate the AC signal very well. I assumed that this circuit is an input to a microcontroller which then will vary the output voltage and frequency. I've added info to my answer. Cool name, by the way :) – bitsmack Aug 06 '19 at 06:51
  • That's a good point. I take it back then. Blame my tiredness for the oversight. :D And thanks, your name's quite fine also. :) – Richard the Spacecat Aug 06 '19 at 06:54
  • Ah, no, I'm glad you mentioned it! It made me improve my answer a bit :) – bitsmack Aug 06 '19 at 06:55
  • Thank you for the digital potentiometer, I will try that as soon as I receive them. @RichardtheSpacecat : not exposed to high voltage as it's the control stage for the mosfet on the primary side of the transformer. – xoxu Aug 07 '19 at 00:39