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| 0-10V controlled via I2C |
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| permal:
--- Quote from: Kleinstein on July 21, 2018, 01:31:13 pm ---When using a digital pot, keep in mind the voltage at the pot must be inside the supply of the chip. So it would need a digital pot for at least 10 V - the normal ones are 5.x V max. --- End quote --- Yeah, I noticed that when reading a datasheet for one of the available ones. I connected a regular 100k pot, the result wasn't what I expected. Yes, the lights can be dimmed, but it all happens within the lower ~20% of the scale. Why specify 100k when the entire dimming happens within the lower ~20k? |
| Zero999:
--- Quote from: permal on July 21, 2018, 12:00:04 pm --- --- Quote from: Hero999 on July 21, 2018, 10:05:15 am ---There's no way you need 35mA for that. The LM358/LM2904 will be fine on its own. If you really want more current, two channels can be connected in parallel, using current sharing resistors. See the application note linked below: https://www.intersil.com/content/dam/Intersil/documents/an11/an1111.pdf --- End quote --- The datasheet states "Light regulation 0-100% by means of PUSH function, 1...10V interface (I=0.35mA) or 100 Kohm potentiometer.", that's where I got the number from. Thanks for linking the AN, I learned something new. --- End quote --- You got the decimal point wrong. 35mA, is 100 times 0.35mA. |
| HB9EVI:
--- Quote from: permal on July 21, 2018, 01:52:24 pm ---I connected a regular 100k pot, the result wasn't what I expected. Yes, the lights can be dimmed, but it all happens within the lower ~20% of the scale. Why specify 100k when the entire dimming happens within the lower ~20k? --- End quote --- could have caught a logarithmic pot perhaps? |
| james_s:
A DAC seems a bit extreme for this application. How about a PWM output from a microcontroller with a RC low pass filter? To get the voltage up to 10V you could either use an op-amp to amplify the resulting DC level, or buffer the PWM signal prior to the low pass filter. |
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