I’m working on a project which controls some LEDs as well as a 20ohm resistor heater. Whenever the heater is toggled on I get a dimming in the LEDs. The power supply is a 75w switching laptop power supply feeding 18v and the schematic is attached. While not reflected in the image - all tip120 transistors actually have a 330ohm resistor between them and the ATTINY. I’ve tried this on a NANO as well and I still get the dimming.
The LED panels are 18v and pull ~150ma per panel. There are three panels total (LED1 consists of two panels in parallel).
Thinking that the power supply was somehow the cause I went ahead and built a power supply along with dedicated switching regulators per panel to bring the output 18v (PS output is 24v with just the LEDs and Tiny/Nano on and 20v with the heater and everything else enabled) and I’m still seeing the dimming. I’ve even removed everything but one led panel and just toggled the heater on and off every two seconds in my program and the dimming is still there :(. I checked the output voltage on the LED output pin just to see if maybe there was voltage droop when the heater is toggled on but the output voltage is steady on all of the control pins.
Any help with this is very very much appreciated.