reverse polarity automatically

Discussion in 'The Projects Forum' started by rhhince57, Oct 25, 2009.

  1. rhhince57

    Thread Starter New Member

    Oct 25, 2009
    I have a 4-30 current controlled setup. At 6VDC, I am able to maintain 5mA constant. I switch polarity by means of simple switch. The switch is made after the constant current. I would like to switch polarity automatically. What is the simplest circuit to do that? I would like to see a switch made about every 5 minutes or have the ability to increase or decrease the timer, but 5 to 10 minutes would be ok. As I am not an electronics expert I need the simplest solution. I managed the constant current with a few resistors, a diode, and some other 3 connector thing of which I do not the name. Any help would be greatly appreciated. Thanks!
  2. russ_hensel

    Distinguished Member

    Jan 11, 2009
    a 2 pole relay or an H bridge could do the switching. For timing a 555 circuit or a microcontroller would be good. If you are calling transistors a "3 connector thing" this may be a bit advanced for you. A 555 with a booster transistor connected to a relay may be the simplest. 5 minutes is a bit on the long side for a reliable, simple, 555 circuit. See what others say.
  3. SgtWookie


    Jul 17, 2007
    See the attached; it should do the trick for you.

    The R1/C1 combination gives a minimum total cycle time of about 5 minutes when R2 is at minimum resistance.
    When R2 is at maximum resistance, total cycle time is roughly 10 minutes.

    If you really want to go up to 10 minutes on/10 minutes off, replace C1 with a 1000uF electrolytic capacitor. Voltage rating should be 60V or more so that capacitor leakage current will be low.
  4. rhhince57

    Thread Starter New Member

    Oct 25, 2009
    I may just go ahead and order the parts and give it a shot. Thanks!