Question with a prop1, LED and a solenoid valve

[Jeff]

I have a quick question for anyone. 

Using (2) 12vdc solenoid valves and (1) LED light with my prop1  Why will the LED dim when the 2nd solenoid get power?

I?m using a 12vdc 1000ma for power.  So my power supply has enough power. 

Thanks for any help

[JonnyMac]

The LED is brighter without the valves because there's not much of a load on the power supply and it's drifting up a little bit, probably close to 13v.  Once the valves operate and the power supply starts regulating more stiffly you have a slightly lower voltage across the LED, hence it's a bit more dim.  You could always run it from a TTL pin header (at 5v, so you'd need to change your current limiting resistor) which is very solidly regulated to 5v -- you wouldn't see any brightness change regardless of what's going on with the valves.