MSA-R DC loads

[John]

B. writes:

I bought a...MSA-R. Your site said it can switch 24V AC. What could it handle if I switched DC?

Up to 24VDC will be ok, as long as current draw is below the maximum.

If you have an inductive load, you should also make sure that the "inrush current" is also within the maximum switching current, to prevent the relays from "sticking".

Hope this helps...

[alski]

B. writes:



Up to 24VDC will be ok, as long as current draw is below the maximum.

If you have an inductive load, you should also make sure that the "inrush current" is also within the maximum switching current, to prevent the relays from "sticking".

Hope this helps...
I recently built the MSA-R and everything is working except that the relays are not opening the circuit after the midi note is released. This seems to be the 'sticking symptom you described. I don't know the exact current requirements of the 12V solenoids I ordered surplus. Is there any way to prevent the relays from sticking? Also, I'm not sure what you meant by "inrush current". If I had to guess, the solution to this would involve adding resistors, but I would like some expert advice.

Thank you very much in advance for your help.

[John]

I recently built the MSA-R and everything is working except that the relays are not opening the circuit after the midi note is released. This seems to be the 'sticking symptom you described. I don't know the exact current requirements of the 12V solenoids I ordered surplus. Is there any way to prevent the relays from sticking? Also, I'm not sure what you meant by "inrush current". If I had to guess, the solution to this would involve adding resistors, but I would like some expert advice.

Thank you very much in advance for your help.

"Inrush current" is a spike of high current that occurs when the solenoid is first switched on. You can read about this elsewhere on the web if you search for it.

You're correct--one way to limit the current is to add a series resistance with the solenoid. It won't hurt to try a larger value, then work your way to smaller values if the solenoid does not fire with the resistor in place. Just make sure that the wattage of the resistor is large enough--otherwise, you'll burn up the resistor.

Here's some info about calculating the current flow & power dissipation in a resistor:

http://www.kpsec.freeuk.com/components/resist.htm

Hope this helps.