Automated DC Motor Forward/Reverse/Brake

Discussion in 'The Projects Forum' started by BiomedEngineer, Nov 14, 2012.

  1. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    Hello all!

    I am fairly new to circuit design, I have some background but not too much. What I need is a pretty simple circuit to control a DC motor. The motor needs to go in clockwise position to screw in a screw shaped device. Once the screw is in it will need to stop automatically (proximity sensor?). After an adjustable amount of time (around 30 seconds) the motor will reverse and unscrew and stop automatically. This will repeat for a series of about 5-7 days to give you an idea of how robust it must be.

    I am not really sure the best way to achieve this. I have looked into 555 timers, DPDT relays, and H-bridges. I am not against off-the-shelf products and price isn't too big of a concern.

    Any help would be appreciated!

    Thanks. :D
     
  2. MrChips

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    Oct 2, 2009
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    Does it have to be a DC motor?
    What is the current, voltage, power and torque rating of the motor?
    Can you replace the DC motor with a stepping motor?
     
  3. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    It does not have to be a DC motor. I do not actually have a motor yet because I can get one to suit the circuit design.

    Forgot to mention that sorry!
     
  4. MrChips

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    You have to provide us with some information on the kind of load the motor has to move.
    Also distance of travel, speed, resolution, etc.
    I stepping motor might be a better choice if we were given more info.
     
  5. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    The screw will be pushing a rod by screwing in. This will be a very small amount of load (max 2 lbs, probably a lot less). The screw will travel about 1 in. The screw has not been designed yet either so threads can match design. This will have manual stops so there would not be a risk of screwing too far, but I wouldnt want the motor to burn up. Speed is not really set in stone, pretty flexible there. If I had to guess... around 1-3 seconds for it to screw in the 1 inch.
     
  6. MrChips

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    A load of 2lbs might be considered moderate to high for a small stepper motor.
    You did not give step resolution.
    Perhaps a photo of the physical setup would be helpful.
     
  7. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    5 degrees per step would be more than enough. 2 lbs might actually be a bit of a stretch. Most likely 1 lb would be sufficient. This is still a prototyping phase so there is no physical setup yet. The idea is to move this rod in and out by the automated rotation of this screw in and out.
     
  8. MrChips

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    Find an old computer with a 5.25-inch floppy drive and you will find a stepper motor that moves the disk heads in and out by more than an inch.
     
  9. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    Haha ok, that takes care of the motor.

    But, I am really more interested in the circuit design itself. How would I be able to control this motor so that it automatically spins one direction, stops for x seconds then reverses and stops for x seconds. and repeats this indefinitely or until power is switched off?
     
  10. MrChips

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    That part is coming up and it is not difficult.
    What resources do you have? How do you want to control the motor, from a PC, laptop or a dedicated black box?

    How do you want to input the x seconds?
     
  11. shortbus

    AAC Fanatic!

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  12. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    That is perfect!

    As far as controlling it, I would need a dedicated black box. This needs to be stand alone besides power supply. Ideally it would have a dial that would turn that would have set times for the delay between the screw in and screw out. And in a perfect world you would be able to independently control the delay after screw in and screw out (ie screws in waits x seconds, screws out and waits y seconds. As opposed to x=y).
     
  13. MrChips

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    The electronics world is a perfect world (almost). You give us the specifications, we deliver.

    State the actual range of settings for x and y, for example:

    x = 0 to 180 seconds, ± 1 second, typical usage 5 to 25 seconds, ± 1 second.
     
  14. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    Thats actually right on.
     
  15. John P

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    Oct 14, 2008
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    I think if you haven't got much background in electronics, but you're willing to get into a project that does require some technical skills, then the Picaxe is a good way to start. It's a microcontroller (single chip processor) designed for very easy programming in terms of both software and the hardware connections needed to make it work. Compared with other processors it can't do much, but if what you want is to do sequencing and timing, it sounds just right.

    http://picaxe.hobbizine.com/
     
  16. BiomedEngineer

    Thread Starter New Member

    Nov 14, 2012
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    That looks very interesting, I will look into it!
    Thanks.
     
  17. Bernard

    AAC Fanatic!

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    Here is an outline of a simple relay system. Motor gear reduced DC, about 1:4. If driving 1/4, 20 all-thread ,output shaft is 1200 RPM for 1 in travel in 1 sec. SW 1 &2 are NC limit switches. Going UP SW1 opens, triggering U1 for 1-100 sec, @ time out relay driver U2 closes Ry which in then latched by contacts via SW2 to +. Going down, SW2 opens triggering U3 which keeps Ry closed for 1-100 sec. At time out motor srarts Up.
     
  18. Bernard

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    Similar project: For Hemo-iridation, 60 ml of blood is extracted ther re injected, 5 min each way; this device uses a motor to replace tech.
     
  19. Bernard

    AAC Fanatic!

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    Screwed up again, lost top view. now need 10 words.
     
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