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Reversing polarity (not for a motor)

Discussion in 'Sensors and Actuators' started by penumbra, Jun 14, 2013.

  1. penumbra

    penumbra

    1
    0
    Jun 14, 2013
    Hi everyone,

    I'm a software engineer by trade and just starting to mess with electronics via Arduino.

    My first project is to connect a WWII-era wind speed and direction set to the internet to display NOAA buoy data (also a sailor).

    I have no data on the the wind direction gauge, so I've been working towards reverse engineering it. There are three terminals on the back. By giving each one different polarity (+, - or off), I can rotate the arm. It seems to be driven by electro-magnets.

    I'm thinking the answer is to use a transistor setup and the Arduino to set one of the three states for each of the pins, 12 states in all. I've read up on H-bridges and they would meet my need, except I believe I need another "leg" to support the third pin on the gauge.

    I think what I would need would be a transistor with 3 SPDT switches. Here's a little diagram:
    https://www.circuitlab.com/circuit/ma5qm7/wind-direction/
    Edit: 5 min later, I realize there needs to be three states to each switch: +, - and open (off). Meaning my diagram is wrong. Oh well, I hope it helps get the idea across.

    As a final wrinkle, in order to get accurate display, I will need to PWM the voltage to the pins. So, just a relay wouldn't cut it.

    Any thoughts would be greatly appreciated!

    Thanks,
    P.
     
    Last edited: Jun 14, 2013
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