12V testing circuit

126

02:03:07

Trying to build a circuit when 12V is reached to top LED will light up, anything below this and it must be dead.  The circuit on the right has a zener and those on the left have relays, quite obvious.

 The Zener I'm still puzzled with as it only dims when the voltage drops below 12V.  Any suggestions for it to 'die' when just unted 12V? 

The relay seems to be working nicely.  The top circuit is the intended for DC where the circuit below just shows how it will react in real life. You can get resistors of that rating, I went for 0% tolerance.  The relay I'm not to sure of yet but will keep you updated later. 
The indication of the LEDs is as follows:
Blue - System on
Green - 12V OK
Red - Below 12V

published 11 years ago

applechr

11 years ago

Reverse ur zener diode. Make the top led run at 2v. Change the resistor to 300 ohms and then it should be on @ 12v and turn off when below 12v

Elmo

11 years ago

Thanks @applechr, I hope I did what you suggested. I've added an AC source just to see wat it will do. I've also built a circuit using a relay and I prefer this one better for showing the 12V switch exactly. What do you think?

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