| Electronics > Beginners |
| diy momentary switch |
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| andrewlapham:
I'm looking for a way to power a small form factor pc using the car ignition. As the power button on the device is momentary I will need a solution that only makes continuity for a short time. I know my options are using momentary relays and or microcontrollers but I would like a more hands on solution only using standard components. I have plenty of regular relays, transistors and many other basic componants, any ideas? |
| ledtester:
What kind of operating logic do you want? Will the PC be connected to the car's battery all the time or only when the engine is running? Do you need to be able to sense when the engine is running and when it is turned off? Are you just looking for a simple RC timer circuit which will generate a digital pulse after power is applied? If so search for "monostable multivibrator" or "one-shot multivibrator". A quick Google search for "car pc power supply" brought up commercial products like this one: http://www.mini-box.com/M4-ATX The "survives vehicle engine cranks" feature is noteworthy as the automotive electrical environment can be very noisy. Update 2... (removed the youtube video since it uses relay) this circuit is probably more what you want: https://daycounter.com/Circuits/Pulse-Circuits/Pulse-Circuits.phtml |
| andrewlapham:
Hey, thanks for the reply. So I want the PC to receive the power on signal when the car is turned on. I'm not too worried about a graceful shutdown as I can send shutdown commands via SSH. Can the transistors in this example be replaced with general purpose componants like 2n222? |
| ledtester:
Yes - any general purpose NPN and PNP transistors (note there is one of each) should work. |
| andrewlapham:
hey i love this design and am going to put it together tomorrow. have you got any suggestions on how i can keep the circuit safe from spikes and general car electrical noise? |
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