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Help designing resistive wire heating element circuit

Discussion in 'General Electronics Discussion' started by steveh, Mar 7, 2013.

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  1. steveh


    Mar 7, 2013
    I am designing a device that works on the same principal as a soldering gun, but it is much smaller in size and power. I would like it to be powered by a plug-in dc power supply.

    At the business end is a small loop of resitive wire which, when dc voltage is applied will cause the wire to glow red hot. The resistive wire is 29 gauge, 1 inch in length overall, and has a resistance of about 4 ohms. The purpose of the device is to melt holes through thin plastic material.

    I experimented with AA batteries and found that 5 volts is about right to make the loop of wire glow red hot. The voltage on the finished product needs to be adjustable from zero to full power by the user in order to fine tune the temperature of the wire. Also there needs to be a couple of LEDs which are are always at full power, and an on/off switch. So I envision this to be a box with a jack for dc input from the plug in adapter, a dial to adjust the temperature, an output jack for the resistive wire, two LEDs on top and an on/off switch.

    My questions are:
    -What voltage and amperage rating should the wall wart be?
    -What is the best way to provide adjustment of the resistive wire from zero to full power.
    -Will the two LEDs be a problem - can they run on 5 volts?

    Bit of a newbie here... thanks for reading and I greatly appreciate any help.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Sounds like you need just over an amp.

    I would look at a variable constant current source, possibly one of the switchmode ones available for not very much on eBay.

    Power the LEDs from a separate voltage source (lights to illuminate the work area?)
  3. steveh


    Mar 7, 2013
    Thank-you for the help with this. I ended up using an LM2596 DC Buck Module with a 6vdc 2.5 amp supply.Works great.
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