Question regarding diodes in a reversing linear actuator circuit.

Discussion in 'General Electronics Chat' started by nosliw, Sep 7, 2012.

  1. nosliw

    Thread Starter New Member

    Aug 28, 2012
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    I followed the following diagram I found on this site (http://forum.allaboutcircuits.com/showthread.php?t=23249&highlight=automatic+reverse) from SgtWookie for my project. I have a round hay baler that uses a 6" travel linear actuator to move the twine across the bale as it spins.

    I ordered a general purpose DPDT 12v 30A relay (part number PB349-ND) and some 1N4004 diodes from digikey and installed it on my baler. During testing, it worked fine.

    Testing was done with a multmeter turned on to monitor DC voltage before I hooked up the actuator. Both limit switches worked as well as the switch to start the cycle.

    I believe I may have burned out a diode. The system is now "stuck" in one position. The limit switch at s2 works, as it stops the actuator. But linear actuator will not reverse and coil is energized as soon as power connector is plugged in.

    Am I using the right size diodes for a 12V system with an actuator that could draw up to 20 amps under full load? (if i remember correctly when I bought the actuator) it may be 30 amps.

    Thanks.

    Conn
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Oops, the 1N4004 diode and all 1N4000 series diodes are rated at 1A continuous.
     
    nosliw likes this.
  3. nosliw

    Thread Starter New Member

    Aug 28, 2012
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    what would be the correct diode for me to use?
     
  4. MrChips

    Moderator

    Oct 2, 2009
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  5. nosliw

    Thread Starter New Member

    Aug 28, 2012
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    Much thanks!
     
  6. mlog

    Member

    Feb 11, 2012
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    36
    Isn't the diode just a free wheeling (spike suppression) diode that only momentarily conducts? The 1N4000 series are rated at 30A surge. How much current could the coil draw?
     
  7. crutschow

    Expert

    Mar 14, 2008
    13,028
    3,237
    But that surge is typically only for a short time (such as a half the mains sine-wave period). If the motor applies its transient longer than that it can zap the diode with a lower current.
     
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