Help controlling a 24V wheelchair motor(1 motor)

Discussion in 'The Projects Forum' started by ju5t_h3r3, Nov 23, 2012.

  1. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
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    Hello all,
    I've found some great write-ups on how to control 2 wheelchair motors for robotic projects, but a lot of what I'm reading is over kill for what I plan to use the motor for, so I need some help for a simple control unit.
    Here is the plan I would like to control a wheelchair motor to operate a stationary archery press. Here is what it looks like
    http://i290.photobucket.com/albums/ll263/iskunkedyou/press001.jpg

    What I would like to is control the press with a foot pedal hopefully a forward and reverse pedal and off when the pedal is not in use. I am interested in having the brake applied when the motor is not in use.

    I'm not concerned with increasing or decreasing the speed each time with the foot pedal but I would like some type of speed controller to adjust the speed to get the right speed set for the first couple of runs so that it is not to fast as this press is normally hand operated. The load on the jack will range from 70 to 300 pounds, I feel the wheelchair motor will have enough torque but I do think circuit will require handling high amps as it will be a load to press the bow. I will be able to make all the couplers for the motor to jack connection and it actually has a place on the back of the jack to do this so that in case manual operation is required I can still use the detachable handle in the front. This is one reason I chose the wheelchair motor I can use the manual release to operate the press manual. I also wanted it to be quiet operation as I have already hooked a black and decker 7amp 1/2 ac drill to the press to see how it would work, it did fine but was loud, not constant on the speed, and had no brake, but worked as a power motor for the press and pressed the bow just hard to use daily.

    I plan to get a AC to DC power supply to run this as it does not need to be battery operated.

    At this point I have wheelchair motors 3 sets that were salvaged from running chairs, but I'm open to suggestions if you know of anything better for my application.

    Key points are forward and reverse foot pedal, the motor stop/brake when the power is removed, speed adjustment so that the rate of pressing can be set to a safe level(full throttle would be uncontrollable) but once adjusted it would be left there, an AC to DC power supply that would handle the amps and supply the volts need.

    All of this can be wired as there is no need for remote operation.

    I have developed a cramp from pressing bows by hand and really need this to make my daily life easier. Yes there are other brand powered bow pressed but the versatility and durability of the xpress is what I need.

    I'm fairly mechanical minded so I can follow instructions and simple schematics I just have not found tons of info on the wheelchair motors and what I have found refer to robot projects so I'm reaching out for some help from you guys to see if this can be done. I'm willing to purchase components so not looking for circuit creation but more or less an off the shelf parts to DIY motorized X-press.

    Any help is greatly appreciated and thanks in advance.
     
    Last edited: Nov 23, 2012
  2. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
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  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Look at the references at the bottom of this post, listed as Tags, esp. wheel chair & down to 22Vdc wheel chair motor. I used a center off SPDT toggle SW for direction & 4 MOSFETs, 60 A in parallel, biggest problem was start-up over current protection.
     
    Last edited: Nov 23, 2012
  4. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
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    Question?
    I looked in the 22VDC thread here is what I think I have come up with:

    If I use 12 volts that will slow the motor some because of less voltage but what does that do to torque?

    To press a bow it does take some force. The motor is from a Jet 3 and I have a pair of Jet 7 motors, from what I have researched these are the same motor for both models.

    Here is the off the shelf items I'm looking at

    http://www.mpja.com/12V-17A-Phihong-Power-Supply/productinfo/18091+PS/

    http://www.mpja.com/24V-125A-Hengfu-Power-Supply/productinfo/16489+PS/

    http://www.electronickits.com/kit/complete/motor/CKMX066.htm

    http://www.mpja.com/DPDT-Foot-Switch-Center-Off-Rocker/productinfo/18153+SW/

    I assume the controller will allow the speed of the motor to be the same no matter which direction the motor is going.

    So which below is the correct connection:

    The circuit would be 120vac input to dc power supply(12 or 24 which ever is recommended) then DC power supply output to foot switch, then foot switch to PWM controller input, then controller output to motor??

    or should it be:

    The circuit would be 120vac input to dc power supply(12 or 24 which ever is recommended) then DC power supply output to PWM controller input, controller output to foot switch, then foot switch to motor??

    Any help is appreciated. and I'm open for suggestions
    thanks in advance
     
  5. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
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  6. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
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  7. Maketronic

    Active Member

    Mar 21, 2009
    49
    0
    Hi there
    Assuming that your wheelchair motor is just a normal DC Motor and assuming that the power supply and speed controllers are capable of delivering sufficent current, your bottom 2 listings would work.
    These are things you swould have to look into, if you have access to a dc clamp meter this would probably be these best way to measure your current.
    With regards to the 'Normal DC Motor' thing all you have to be careful is that the motor is not a brushless motor (in which case it would have either internal or external electronics to supply the required pulses).
    Does the motor have just 2 wires, and does simple connection to a battery result in the motor turning normally. If the answer to these 2 questions is yes chances are the speed control would work.
    With regards to running it on a lower voltage be aware this will compromise torque of the motor (Torque even compromised running at a lower speed through a speed control).
    Hope this is of some help to you.
     
  8. ju5t_h3r3

    Thread Starter New Member

    Nov 23, 2012
    6
    0
    Yes is a regular motor. 2 wires other than the 2 wires for the brake. I have seen the current draw is between 4 amps no load and 8+amps under a load. So I am preparing for a load with high torque. I will go with 24 volt supply, and a high amp output to help with startup Amps. I ordered the controller. No have to find the foot pedal and the right power supply which I think is the one I have last listed.
    Looking for any extra thoughts or better suggestions for the foot pedal and supply.
    thanks again in advance.
     
  9. Maketronic

    Active Member

    Mar 21, 2009
    49
    0
    Hi

    Sounds like you are well on the way.
    Any pedal that has a spdt switch could be used for your fwd, rev.
    See http://www.ebay.com/itm/1pcs-CFS-01...918?pt=LH_DefaultDomain_0&hash=item19d401d796

    Just connect the C terminal of the switch and and the cw and ccw terminals to the NC and NO terminals, if it goes the wrong way swap them over.

    Alternatively if it were me I would use a variable resistor like http://www.ebay.com/itm/NIB-Linemas...559?pt=LH_DefaultDomain_0&hash=item2c6a2341ef to control the speed and a normal toggle switch as a fwd/ rev.

    If you are driving a lead screw under reasonable loads you will probably find that the brake is not neccessary because the friction from the load will quickly cause it to come to a stop.

    Alternatively if you dont have your motor yet a linear actuator off ebay may well suit your purpose as it will have motor, lead screw and limit switches in one package and is designed for high loads.

    Best of Luck
     
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