Enhancing Circuit Design: Adding a Second Solenoid in Parallel

[marcktz]

Hi - I am designing a circuit with two solenoids (12 V, 1 Amp each) in parallel in order to get power of two upon activation using an arduino.
I am able to wire one solenoid using 12 V adapter rated 3 Amp, 1 TIP120 darlington transistor, 1N004 diode and Arduino connected to base of the transistor. It works, however I want to add another solenoid in parallel, what else do I need in this circuit? attached is the circuit for one solenoid.

 

[jim hardy]

4001 is a one amp diode so 2 amps , one from each coil overloads it slightly,
but it has good surge capability .
Coils are about 12 ohms ?( 12v 1 amp)
Just tack your other solenoid and its diode right in parallel
But with about an ohm in series with each of the diodes so they'll share flywheel current equally
1 ohm 1 watt should do well and last forever, unless you're cycling these solenoids on - off rapidly for a long time. Then go to 2 watt.. Or use a single two amp diode.

my two cents (overpriced at that)

old jim

 

[rbelli1]

Another option is to just double the circuit you have there. You then have the option of using half force if you need to conserve energy. For example if your device requires both solenoids for actuation but a lot less to keep it in the final position.

BoB

 

[berkeman]

what else do I need in this circuit?

I would add decoupling capacitance across your 12V source. Probably a 10uF, 25V electrolytic in parallel with a 1uF ceramic cap.