Help making a controller for 12v actuators

Discussion in 'The Projects Forum' started by sandmanio, Mar 21, 2010.

  1. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    I have a project that has 2X 12V actuators http://www.firgelliauto.com/product...d=130&osCsid=6ee4e14916cdaba0ff2178f50a1eb9b7

    I need to make something that automatically moves both of them at the same time to fully extended position and holds it for 30 minutes and then retracts completely for 30 minutes and cycles this pattern.

    The actuators are very simple just 2 wires. They have built in limit switches too.

    Can anyone offer any suggestions? I dont know much about building electronics but Im sure I can put together a breadboard or something. Hoping to be able to get all the parts I need from Radio Shack or Frys electronics. Thanks for any help you may offer me.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Can you explain your application a bit more?

    The reversing of the current direction to the motors isn't a big deal using relay(s).

    However, since the limit switches are internal to the actuators, that means leaving at least one relay coil activated for 30 minutes at a time (wasting power and heating the relay), or using expensive latching relays.

    Unless, of course, you would care to wire in external limit switches for both ends of both actuators. Then it could be accomplished with a pair of SPDT automotive-type relays that you can get just about anywhere.

    And a timer circuit, of course.
     
  3. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    Its for moving a 2 light bulbs up and down that are attached to the actuators via a wire and pulley, LOL.

    OK so limit switches....What part number from grainger would I need? Is there anyway you could put together a diagram and parts list or possibly link me to somewhere that I could read more? I really dont know much about timer circuits and relays and how to make em do what I want em to hah. I appreciate your time!
     
  4. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    Well after just googling limit switches I am concerned that they may be extremely expensive which would make them a no go for this use. Surely there must be some way of utilizing the internal limit switches although I am half retard. I am hoping to keep the entire cost of the ....uhhh controller?....under $100 for sure.

    I guess it is simply a matter of supplying 12V for about 15-20 seconds (the amount of time it would take to fully travel one direction with a load) and then waiting 30 minutes and supply 12V in reverse polarity for 15-20 seconds and repeat?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    I suppose it could be done that way too.

    The basic reversing circuit can be done by creating an H-bridge using SPDT automotive-type relays (cheap and available everywhere).

    The timing can be done using 555 timers with a few extra parts (resistors, caps, available at Frys or any Radio Shack).

    If you need the timing to be precise, you will need something else besides 555 timers.

    You tell us.

    Attached is a very basic schematic for reversing the current flow through a motor. Don't worry about the voltage or the fact that you have two motors. It's important that you understand how this simple circuit works before you can understand the more complex circuit.

    The 2nd attachment is the same as the 1st circuit, but it has reverse-EMF protection diodes installed. This helps to prevent burning/pitting of the switch contacts. It is also important that you understand that concept before things get more complex.
     
    Last edited: Mar 21, 2010
  6. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    not precise at all really. Approx. 30 minutes give or take 5 minutes should be fine,, or is that considered precise heh.

    Im going to go ahead and google "H bridge" real quick

    SO help me visualize this a bit if you will:

    From the wall plug single 12V power adapter -> somehow connect to a breadboard with the timer circuitry and spdt relays -> both actuators
     
  7. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    thanks I can see how that simple circuit works
     
  8. SgtWookie

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    Jul 17, 2007
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    Here you go:

    [​IMG]

    U1A and U1B are two halves of a 556 dual timer.

    U1A sets the time interval to approximately 30 minutes due to the RC time constant of R2, C1 and C2. R1 is so small in comparison to R2 that it has little consequence on the time. However, it must not be omitted from the circuit.

    Normally, a single timing capacitor is connected between pins 2 & 6 and ground. However, splitting up the capacitance to roughly 2/3 to ground and 1/3 to Vcc eliminates the usual long delay for the 1st cycle upon power-up, as the circuit will start with the timer at 1/3 Vcc instead of ground.

    U1b is used as a (roughly) 20-second timer. The discharge path for C3 is via R4 through Q1. The charge path for C3 is via R5, R4.

    When U1A's output toggles, U1B's output follows roughly 20 seconds later.
    The SPDT relays have diodes in their conduction path, so that RLY1's coil only gets energized when U1A's output (pin 3) is high and U1B is low, and RLY2's coil only gets energized when U1A's output is low and U1B's output is high.

    RLY1 and RLY2 must have coils with a resistance of 150 Ohms or higher. The relays may have internal diodes across the coils; if so, make certain that you connect them so that the internal diodes are connected cathode-to-cathode or anode-to-anode with D5 and D6.

    D1 through D4 are 15v Zener diodes, used back-to-back to "snub" the reverse-EMF caused when current through the relay coil is stopped. You could actually use standard 1N400x series diodes instead, but positioned as D2 and D3; D1 and D4 replaced by wire.
     
  9. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    woah ok let me let this sink in hah
     
  10. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    btw thanks a whole bunch for your time
     
  11. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    alright I just got back from Radio Shack but I am empty handed as they didnt have some parts on the list and I also realized I dont know enough about what I was going to buy anyway haha.

    Couple of questions for ya:

    What watt resistors should I get? i noticed they had 1, 1/2 1/4 and even 1/8.

    Is the 556CN timer the same as a uA556? It looked like it had 7 terminals and it looks like the one in your diagram has 8 but maybe i mistook something. Also I cant find any uA556 for sale on google or anything.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    That happens :)

    In the circuit I posted, you can use very low-wattage resistors. Even 1/20 W resistors would be more than adequate.
    They carry the LM556 dual timer. There may be other letters after the basic part number. It is a 14 pin IC.
    http://www.radioshack.com/product/index.jsp?productId=2062597&filterName=Type&filterValue=IC-Analog

    They also carry the LM555 single timer:
    http://www.radioshack.com/product/index.jsp?productId=2062596&filterName=Type&filterValue=IC-Analog

    Either of the above can be used.

    They also carry the TLC555 single timer:
    http://www.radioshack.com/product/index.jsp?productId=2062595&filterName=Type&filterValue=IC-Analog
    Do NOT buy one of those with the intent of using it in this project, as it will not work. It is a CMOS version, and it will not be able to output enough current.
     
  13. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    oops i didnt see the above post
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    Did you read what I wrote?

    Did you look at the links I posted?

    I don't know how much better that I can explain it.
     
  15. sandmanio

    Thread Starter New Member

    Mar 21, 2010
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    hah no i didnt see the second page and thought my original post didnt make it thats why i edited it
     
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