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Is it possible to connect an led in parallel with a lock mechanism? Answered

I am working on a project. I have a keypad panel that unlocks a door and I want to add in the circuit an led indicator(when the lock is released I want the led to turn on. When connecting the lock with the led in parallel the keypad does not work properly. The lock uses 1amp and the led needs less than 350ma. Would a resistor on the led solve the problem? If yes, what resistor should I use? (it's obvious I don't know much about electronics but I wish to learn...). Any ideas or ideas or advice is most welcome! Thanks community!


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1 year ago

LEDvoltage = The voltage "lost" over the LED for your current you want to push thru the LED. See the Datasheet of your LED what is a normal current. Thats often 2mA, 5mA, 20mA
350mA would be a VERY bright LED and propably white and from a flashlight.

Now do the math:
Resistor = (Supplyvoltage - LEDvoltage) / LEDCurrent

Remember: 5mA = 0.005A and LEDcurrent is in Ampere.


1 year ago

You missed the basics of electrical circuits ;)
The lock most likely uses a simple solenoid type actuator.
This means it will either work on 12 or 24V.
Yours seems to be 12V.
Adding just a LED means you burn the LED out if it was at the correct polarity.
And of course the controller won't like this.
Simply use one of the many LED calculators available online to calculate the resisotr for your LED to run it on 12V.
The resistor goes in series with the LED so that the combination is connected to positive and negative of you lock mechanism.
Like that the LED will light up as long as the lock is energised and go off with it.