Regulated 24v Power Supplies

[ScaryTinker]

I've got a box full of wall warts, problem is how do I tell if any given wall wart is regulated?  Can you tell by powering up the wall wart and checking the output voltage?  If the wall wart is not regulated and there is no load the output voltage should be more than the rated voltage... right?

Thanks

Scary Tinker

[JonnyMac]

If you measure with a high-impedance meter the output should be 24v with a very small load (no load will not work, and a meter is, essentially, no load).  You can use a single 24v solenoid as a load.  If that works, connect it to your prop controller and measure the voltage between V+ and GND with the power switch in position 2.  If the V+ LED is on and the normal power LED isn't, you've got a problem -- the controller, when not running any valves, does not present enough of a load to keep the supply in regulation.  You can solve this by measuring the resistance of the a solenoid, then getting a 5w power resistor that is close to that value; strap this resistor between V+ and GND.  This will keep enough of a load on the supply to keep it from going above the LM3940-5.0 (regulator) input voltage.