Hi All, I’m building the water level sensor as per this diagram
https://forum.allaboutcircuits.com/attachments/uln2004-water-level-indicator-jpg.71611/
My circuit differs only in the output where the LED is in series with a 5vdc SPDT pc board relay. The LED operates nice with 3.7v and exactly 5v appears across the coil.
My problem is, on my breadboard, I needed 80k or less resistance to trip the IC but my sight-glass with brass couplings at intervals for sensor levels provide around 100k. At a little over 100k the IC started to conduct, the LED was glowing but no enough to pull my relay.
I need to keep sensor current as low as possible to minimise electrolysis. Any suggestions on circuit alteration to allow triggering with at least 100k input in series with 12v + to the IC ?
https://forum.allaboutcircuits.com/attachments/uln2004-water-level-indicator-jpg.71611/
My circuit differs only in the output where the LED is in series with a 5vdc SPDT pc board relay. The LED operates nice with 3.7v and exactly 5v appears across the coil.
My problem is, on my breadboard, I needed 80k or less resistance to trip the IC but my sight-glass with brass couplings at intervals for sensor levels provide around 100k. At a little over 100k the IC started to conduct, the LED was glowing but no enough to pull my relay.
I need to keep sensor current as low as possible to minimise electrolysis. Any suggestions on circuit alteration to allow triggering with at least 100k input in series with 12v + to the IC ?