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Help with optical solenoid control circuit

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knoxious

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Hey guys, need some help controling a solenoid with an optical switch.

I want the current to the solenoid to be OFF when the optical switch is blocked, ON when clear.

I've build the attached circuit and I can get a voltage drop when I block the sensor but I can't get the transistors to turn on when the sensor is open.

I'm using HY860F optical switch and I can't find a datasheet.

Help woluld be much appriecated !!
 
hi,
The gain of the 2N3055 is very low in saturation, say 5 to 10, you have a 1K base resistor to 12V, thats only giving a 10mA base current to the 2N3055.

It needs approx 0.5A for a 5A collector current.
 
You can't possibly get 5A through the solenoid from a 12V supply with a 100Ω resistor in the 3055's emitter path. Have you considered using a power MOSFET instead of a 3055?
 
It should work better if you change the 2N3055 to a power NMOSFET. Also make the collector resistor of Q1 about 1kΩ and remove the emitter resistor (or make it perhaps 10k-100kΩ).
 
I would add a flyback diode across the solenoids coil too.

Also why not just use one resistor to limit the current through the LED ?
 
Last edited:
Thanks guys, I will redesign with a NMOSFET and let you review. I've been out of electronics for quite a while (30 years!) and need all the help I can get.
 
Working but I need a longer duty cycle

Hey Guys, got my optical switch/solenoid working. Thanks for the help.

But I need a longer duty cycle. I get rapid oscillation of the solenoid plunger turning the optical switch on and off but I need it to be slower.

How can I add a cap to slow down the plunger action and get a longer duty cycle ?
 
If you want the plunger to move at a fairly constant speed that will be difficult because of plunger friction and inertia. I think it would entail having a high current at switch-on, to overcome stiction, followed by a rapid ramped reduction in current to reduce acceleration to zero. IMO the circuit to do that will need more than just an added cap.
 
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