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Looking to replace LEDs with solenoid driven indicators. Answered

I'd really like to replace some LED indicators with physical on/off indicators, like they used on old NASA spacecraft. To see what I'm talking about take a look at this console from Apollo 14 at the little windows above the switches at the center left. The top row is all "barber poll" the bottom row open.

My initial thought is that I could possibly replace the LEDs with a solenoid that would shove an "on" indicator into a little window when powered, and retract it when powered down.

The problem: I know next to nothing about solenoids and don't know if this is feasible. They'd need at least 1/4" throw and to run at low power if they're going to simply be a drop-in replacement for LEDs. What kind of solenoid am I looking for and does it even exist?


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11 years ago

No solenoid will ever be as low-power as an LED.A better bet might be to run the LED output into a transistor or mini-relay which would act as an amplifier, switching power from a separate source to drive the solenoid. I'd suggest hitting your library for a hobbyist-electronics book with a project that shows how to control a relay from a digital logic chip's output. Then either replace the relay coil with the solenoid, or use the relay to control the solenoid. Remember to allow for back-EMF as the solenoid's power is switched off; you may want a shunting diode to protect the electronics from that.


Answer 11 years ago

Very good point about the back-EMF! I'm absolutely sure I would have fried more than one component before I figured that out.

I'm not sure sure there isn't something out there that can power a physical indicator since it doesn't need to be powerful at all. I found some tiny motors for vibrating pagers/cell phones that run at about 1.5V and pull just 50mA which isn't too far from what an LED draws. I'm going to play with 'em a bit and see if I can rig up something or wind my own tiny solenoid. At very least I'll learn more about solenoids.

Or I could just take this as an opportunity to learn how to wire up some more ambitious projects. :)