Is this schematic good? -- DC motor control

Discussion in 'General Electronics Chat' started by xxxyyyba, Jun 8, 2016.

  1. xxxyyyba

    Thread Starter Member

    Aug 7, 2012
    249
    2
    Here is schematic for DC motor control. Using this I can drive motor in both directions and also send short pulses to motor, to move it only a little bit in desired direction.
    Let me explain schematic in detail.

    PWM controller is powered using 12V DC (Vin). Modulated signal (Vout) is input signal of first DPDT relay. Depending on which relay is energized, direction of rotation of motor is changed.

    D1 and D2 are there because of back EMF protection. D3 and D4 are there to enable me to drive motor in opposite direction when it goes to limit in one direction.

    Using left 4PDT (ON-OFF-ON slide type) I choose whether motor will be powered for long time (as long as one of relays is energized) or for short time (one of relays is energized for short time using pulse signal generated using 555 circuit).
    Lets say that we choosed on left 4PDT that voltage which drives motor is "long" (lets call this first ON position of left 4PDT, it is of type ON-OFF-ON).

    Using right 4PDT (ON-OFF-ON, momentary) I choose which relay will be energized. Pay attention that in whatever "ON" position is right 4PDT, it will short one part of 555 circuit (one side of C2 with pin 2). You will see soon reason for this :)

    When left 4PDT goes in second ON position, then 555 circuit gets power supply (12V DC) and it is ready.
    Right 4PDT now has not only function to choose specific relay (thus driving motor in desired direcion), but also to cause process of generation of short pulse using 555 circuit by short connecting one side of C2 with pin 2 (here is where I found this pulse generator http://www.doctronics.co.uk/555.htm#triggering , thanks to AlbertHall). Generated pulse energize specific relay for short time so motor rotates in specific direction only for short.

    Is this ok? :) Is there something what should be changed? I didn't choose values for capacitor and resistor in 555 yet because I still don't know exactly what will be pulse duration. I have normally closed wtiches, DPDT relays and PWM controller.
    Motor is linear actuator (http://www.ebay.com/itm/Linear-Actu...hash=item41998d672c:m:mCviYhnG5aL1LRiI4QsowiA), it should arrive in few days.
    I should buy other components. Motor amperage is 3A max.
    This is PWM controller I have http://www.ebay.com/itm/162002954574?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT
    DPDT relays are http://www.ebay.com/itm/Relay-Omron...969959?hash=item566775f067:g:hmoAAOSwKsRWFmAP .
    Which diodes should I use for D1, D2, D3 and D4?
    Is this power supply (12V DC) good for this application http://www.ebay.com/itm/AC100-240V-...hash=item4d19df1772:m:mmYVpw9kxcePGAlVHiBpCWQ ?

    [​IMG]
     
    Last edited: Jun 8, 2016
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,912
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    It seems horrendously complicated to achieve your objective (as I understand it).
    Consider one relay (call it RL1) to control direction, the other to connect or disconnect the motor (call it RL2).
    Now RL1 can be controlled by an SPST switch to control direction.
    RL2 can be controlled by an DPDT (centre off) switch using one pole to either connect the coil to Supply voltage (continuously on), or to the '555 output for a short pulse of movement. The other pole of this switch triggers the '555.
     
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  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    It further occurs to me that RL1 and the SPST switch could be replaced with a DPDT switch!
     
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  4. xxxyyyba

    Thread Starter Member

    Aug 7, 2012
    249
    2
    Thanks for replies.
    I'm sure my schematic looks very complicated :D However motor is fully controled using only two switches (4PDTs). Is there any chance that you sketch your idea? :)
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,912
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    Here ya go:
    upload_2016-6-9_9-12-15.png
     
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  6. xxxyyyba

    Thread Starter Member

    Aug 7, 2012
    249
    2
    So in this case motor is controlled using two DPDT switches and one "ordinary" switch?
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Two DPDT switches (one a centre off type) and one SPST relay as the '555 can't supply the motor current.
     
  8. xxxyyyba

    Thread Starter Member

    Aug 7, 2012
    249
    2
    I meant user "interacts" with two DPDT switches and one SPST switch.
     
  9. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,912
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    The user interacts via two DPDT switches. The SPST is the relay contact - no user interaction required.
     
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