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Thread: Dc motor reversing with my computer and relays.

  1. #1
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    Dc motor reversing with my computer and relays.

    I found another forum in here talking about dc motor reversing but lost it. I am working on a small project. Running a 90vdc motor with controller off a computer using control relays. I have the operation functioning with a DPDT switch. I want to be able to start my computer energizing a 3.3v or 12v control relay. Which will send my lift up til it hits a switch. When that switch is mated it signals another relay to complete the down motion of the lift when the computer is turned off. In the last operation I was wanting to put a digital timer for about 1 minute to verify that I have not just reset computer. I have drawn a drawing of my setup I would like but just dont know how to wire relays and switches to make this happen. Any help would be awesome. The drawing was done in word. Might have to zoom in on picture document. Thanks for everything , hopefully some one can help me.
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  2. #2
    Fusion Brain Creator 2k1Toaster's Avatar
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    So you need microswitch contacts for start and stop of the track or you can do it more fancy using current sensors on the motor. Current sensors are usually preferred if this is going to be around humans or if the motors have any power at all. If you stick your hand in the track, the current sensor will sense that resistance and stop versus just using a contact switch the motor will just carry on potentially doing harm.

    Add in a PC based IO controller, and the mechanics along with some code and you are done.

    So what do you have so far? I am unclear what your actually asking. I get the concept and the plan. But do you have, don't have, and don't know?
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  3. #3
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    What I have

    I have the rack and pinon set up and motor mounted and it is all operational by manual DPDT switch. I also have my twolimit switches that are mounted at top and bottom. They do stop operation in both directions. I would need to get relays or micro to make automated. I was asking how to wire relays to have a latching circuit make it go up when power suplly on computer is energized. When it powers off and after a time delay make it go down. Hitting limit switch at bottom. I needed direction to what is the best way to take. Relays? PIC controller? Motor bee? ect. I want it to be safe but I want it to be function without a crazy amount of wiring. Any help would be great. I was thining about a relay board but I need to run the control relay side isolated from dc motor control I think? Thans again in advance.

  4. #4
    Fusion Brain Creator 2k1Toaster's Avatar
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    Relays are by nature isolated. So if you use a relay, it is isolated on the coil side. This would be pretty simple with a micro, but could be done with discrete logic as well. You know what a Karnaugh map is? A couple flip flops and basic logic chips for the control, and then a couple transistors to drive the relay coils and you are done.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  5. #5
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    Karnaugh Map

    I have seen some stuff on K-maps but have not done anything with it. seems complicated but willing to try if it will work for my application. I know what flip flops are( Nand gates really) but again have not worked with them either. I found a website that has some info on this. Ill look into it. Seems like K-map is just a bunch 1 ansd 0's. What do you think I should do? Im up for the challenge. Thanks. where do I start!

  6. #6
    Fusion Brain Creator 2k1Toaster's Avatar
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    Well I'm trying to judge your background. The discrete logic will be substantially more complex and less flexible than a micro solution. But it is always good to use them as building blocks so you can learn more.

    If you want the best solution right now, I would buy a PIC. The PIC10F200 is $0.30 in large quantities, and has 6 I/O pins.

    One input for PC power, one for the top switch, one for the bottom, and that leaves 3 outputs to drive a motor controller. Internal oscillator, and the program memory should be big enough for a few lines of code.
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

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