Pressure Gauge Transistor Problem

Discussion in 'The Projects Forum' started by sicktim, Feb 16, 2013.

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  1. sicktim

    Thread Starter New Member

    Nov 23, 2012
    I am having trouble with using a transistor to change the color of the gauge. There are four wires from the pressure gauge that control the color (blue, amber, white, green) and there are two for power. If the color wires are connected to the positive (12V), then it changes to that color. I'm trying to write a program using arduino to change the color using 4 outputs and 4 transistors. It seems simple: Using the outputs from arduino, connect them in series with a resistor to the base of the transistor and then the collector to the positive and then the emitters to each of the color wires. When I try this, I cannot get enough current to flow into the color wires. I need about 0.15mA and this is possible by connecting +12V to the base (with resistor). But when I connect the 5V arduino to the base, I can only get 0.10mA and this is nobueno for functionality (it does not work). I even tried without a resistor between arduino and base and can only make 0.10mA. I'm baffled.

    Maybe i'm going about this all wrong, any help or tips would be great.
  2. bertus


    Apr 5, 2008

    This is the second time you are posting this:
    Car Boost Gauge

    As car related projects are not allowed I will close this one to.


    PS when you try again a ban will follow.
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