Tram control - DC Start, Stop, Rev, Limits

Discussion in 'The Projects Forum' started by eshermer, Aug 7, 2010.

  1. eshermer

    Thread Starter New Member

    Aug 7, 2010
    Ok, I've run out of time and need to build a friend a controller for his homemade TRAM as he calls it. It is a trolly that one will sit in to go down a steep hill to the lake.

    He has the following DC Motor

    GE 1HP shunt wound motor.
    Voltage: 90 arm. & 100 field
    Amperage: 10.5 arm. & .76 field

    (Does this motor have brushes?)
    (Would it be easier to get another motor?)

    So the goal is from either the top or bottom of the hill to manually push the FWD (or down) button. The Motor then lets a winch cable out until a limit switch is hit (ie latches ON-then shuts off) or the STOP button is pressed.

    To go up, the motor is reversed and tightens the winch until the limit or until STOP is pressed. There is going to be 4 limit switches - two at each end and a buffer of distance between them. It would be nice that the controller would ignore the limit if the other direction is pressed. That is, if going down and the limit is reached the cart would go back up without having to reset the limit. The 2nd limit on the same end would require one to move the cart and will be used as a safety.

    I explained the liabilities of latching and the lack of control and that your in for the ride until you hit the limit or if somebody else is standing by one of the two button boxes has control over you. Phase two, is I plan on making a wireless interface to this with a garage door phobe.

    I've found several solutions to speed control, but it would be nice if it was in all-in-one solution.

    My question is there a specific DC control device out there that you can recommend for $300 or less? I've searched Fleebay and read a lot on this useful site on general info, but haven't found anything specific.

    I already have the limits and two sets of FWD, REV and STOP.

    This "controller device" obviously would have to be compatible with the motor and have inputs for the FWD, REV, STOP and limits and hopefully speed control. Another obvious requirement is the controller should be able to handle the case where both up and down buttons are pressed at the same time.

    I've dealt a little with PLCs 15 years ago in college, but after reading about ladder logic again it is very fuzzy. I could relearn if needed. Same goes for the PIC chip, and honestly I dunno if I have time.

    I know this maybe a pipe dream, but after farting around so long I'm out of time. Maybe I have to design something, but I didn't want to reinvent the wheel.

    Although I'm a EE, I am sad to say this simple task is starting to kick my but and it's going to get cold in MN soon.

    BTW-I'm just charging him for parts so this is not something that I will make money off of. While reading the forums I saw that some are making money off from others sweat...Grrr, one of my pet peeves.

    Any useful suggestion are appreciated! I thank you for your time.

    Feel free to ask questions and it's 3am now so I gotta go to bed.
  2. John P

    AAC Fanatic!

    Oct 14, 2008
    There are a few issues to be concerned about here. If this gadget operates on a hill, is the load sufficient to run it back down without power? If so, your motor is acting as a brake in the downhill direction. It's possible to do this, but you have to plan for it. Speaking of brakes, have you considered an automatic safety system of the kind elevators use, where if the cable slackens, springs drive bolts out into the rails? I don't think I'd care to ride it otherwise.

    A shunt wound motor of this size sounds like an antique. Nowadays they're more often the permanent magnet type. But yes, it has brushes.

    You shoud be able to find a controller for a 1hp motor for less than $100, though that would just be for a single direction. You'd need a relay to switch directions.
  3. eshermer

    Thread Starter New Member

    Aug 7, 2010
    The cart itself weighs a few hundred pounds. We already know the cart will move down the hill with gravity and the huge old motor is already interfaced to the winch, so that's why he wants to use it. He actually already has a SCR controller that I was starting to interface too, problem is if it broke (or already is) then repair for him would be difficult. I don't want to be married to this thing. Again, the SCR came with the motor/winch that has been sitting for 20 yrs.

    I was unable to find a decent 12VDC latching relay. I started to use a KUP5D15 and found that the stupid thing does not following the data sheet that states it is NO. Instead it is last state. I found others complaining about this on Google too. Grrr

    I was hoping to buy two all-in-one controllers and set one aside for a spare.

    @Anybody-Can you give a URL where one can purchase such a controller and elevator safety device. I don't want to sound demanding, but I'm running out of time. Great input on the safety device by the way John P. I appreciate it.

    I was stuck for about 4 hrs 70' in the air about 15 years ago in a "window washer's chair" (boatswain's chair) while sandblasting a tank due to one of these safety devices. Finally they rescued me by tugging several times hard on the safety cable. I called my relatives a few names that day.

    We plan on using some cement blocks to simulate a riders weight for the maiden voyage(s). I have found an all in one slow winch with no limit inputs and costly at $1500. Anybody know of one with speed control and limit inputs?

    I was hoping others could chime in with some details - like URLs of such devices.

    Any constructive or safety inputs are appreciated. Awesome site. I'll help out on the site when I get some time in the future, but gotta get this done first.