Aquarium Transistor switch

Discussion in 'General Electronics Chat' started by 559red, Jul 3, 2013.

  1. 559red

    Thread Starter New Member

    Jul 3, 2013
    I was searching the web trying to see how to use a transistor as a switch for a < 1vdc trigger to completely turn off aquarium LEDs based on a 0 - 10 vdc signal from an aquarium controller. I found several sights, but this one was the most clear and provided a great explanation. I will certainly come back whenever I have electronic circuit questions.

    How to I choose an NPN transistor for my application? Are there different specs I need to consider? I will have a 0 - 10 vdc signal on the base. I am considering a small potentiometer to have some control of the cutoff point. Is 10vdc too much for the base? The c - e side is a 5vdc PWM output. It just want it shut it completely off when I get somewhere < 1vdc on the input signal.
  2. MrChips


    Oct 2, 2009
    Yes, 10VDC is too high for base control considering that you only need 0 to 0.7V.
    More importantly, you need to limit the current through the base-emitter junction otherwise you will blow the transistor. Putting a resistor of about 1k to 10kΩ in series between the control signal and the base will limit the current to a safe value.
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Ah.. the old meanwell's do not turn off completely when dimmer voltage is as low as you can go issue.

    Does your reef controller not have outlets? I simply plug my meanwells into my controller outlet box and turn off that relay/outlet when the lights should be off.