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EGT warning light mV switch into V?

Discussion in 'General Electronics Discussion' started by Plimptonjr, May 23, 2013.

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  1. Plimptonjr

    Plimptonjr

    1
    0
    May 23, 2013
    I'm trying to whip up an EGT(Exhaust Gas Temp) warning light for a vehicle I own. Nobody sells a simple warning light and I don't need another gauge in the car. The probe (Thermocoupler) used reads in thermoelectric milivolts. I want to turn on an led in the dash when it reaches 1300 degrees F which is roughly 29.-30mV. I've put a lot of thought into this only to realize I am a complete noob and can not figure out how to set this up. :(
    I've thought about using a thermocouple amplifier with a resistor and transistor but i guess I fail to understand the comple workings.

    I'd ultimately like to power the LED via 14V (Battery) source and thought about a series of transistors used as switches could work. A problem I am facing is the power supply via EGT probe is completely independent.

    The Probe has one red(Ground) and one yellow(Power) sending in mV from 0-40mV
    Battery is 12-14.5V and I will be obtaining power via 5 amp fuse in fuse box

    Help Please??:confused:

    (If it helps, they sell EGT thermocoupler amplifiers to step up the mV output into a 0-5V using the vehicles Battery. If it is recommended to make this project possible, the 1300 degree F warning would be sent as 3V.)
     
    Last edited: May 23, 2013
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    What you need is a comparator. If you use one that includes ground in its input range, you can simply set the - input at 29mV via a voltage divider and put the output of the thermocouple on the + input. when the temp exceeds 1300V the comparator will then go high.

    Bob
     
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