External Limit Switches for Firgelli Linear Actuator

Discussion in 'General Electronics Chat' started by mrstair, Sep 21, 2013.

  1. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    I am setting up a Firgelli Actuator to drop down a large flat screen TV. Because the ceilings are higher than average, I am using a 60" stroke actuator.
    As the TV weighs 125# and the lift hardware another 25# to total 150#, The internal limit switches malfunction at the (internal switch) limits.

    So, I have duplicated the internal limit switches, diodes, and wiring externally. So far so good, the external limit switches work, BUT

    My concern is that the new external limit switches run by the actuation point by 1/2".

    I also have hooked up a Firgelli supplemental lower only limit switch that comes with their remote control package. This added limit switch also runs by the limit switches 1" or so. With the 150# load added, this added external limit switch "ran by" as much as 3". The remote control controls stop the linear actuator IMMEDIATELY. Is there an expensive Train Wreck pending?

    Does anybody know why the stopping action is different?

    After extensive online research and Firgelli "support" the only feedback is that a relay might be helpful on the new external limit switches.

    This actuator is the same as the subject actuator in an extensive post SgtWookie was helpful in titled "Limit switch for actuator help".

    I have attached a wiring diagram and specs for the external limit switches.
     
    Last edited: Sep 21, 2013
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I going to make a wild guess that however your internal limits worked, they would short the motor to achieve the instant stop. Your setup doesn't do that, so it coasts to a stop.

    Your drawing says your p/s is .50 VA. Are you sure that's right? Seems way too small. What's the part # of your suppy?
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,534
    2,369
    Sounds like the application could use a DC brake on the motor, if the motor has a rear shaft, one could be fitted.
    Dynamic braking would be of little use in the application I think.
    Max.
     
  4. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    THANKS very much for the replies. I have very limited aptitude in this area. Based on my limited research understanding on this very helpful site, both replies may be on the right track .... coasting stop vs braked stop.

    To give as much info as possible to help solve this problem:
    1 There is a small circuit board inside above the motor housing (see attachment1) that the small red and black leads go to. The separate motor leads are also off of this board. These (small R&B) leads are visible going into the top of the track. Ignore the (larger R&W) leads - these go to an unused power supply for a manual up/down control. I cut these (small R&B) leads and connected a duplicated external wiring of the internal limit switches wiring. However, there is a tiny IC board that the M7 diode is soldered to (see attachment2). Could this IC board account for the braked stop when using the internal limit switches?
    2 (see attachment3) label on the remote receiver/power supply. The power label could be interpreted max.(space)50va.

    Another thought: After the basic (brake stop) problem is solved, should there be an additional "fail safe" limit switch just in case the first fails/malfunctions? There could be a very expensive "Train Wreck" if this 125# TV somehow falls "off the track". :-(

    THANKS in advance for your assistance.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,534
    2,369
    There may be a possibility for the worm drive to be extended and a brake fitted?
    It would appear to me that for this application, an electrical O.T. detection may not be suitable, It would need some kind of physical stop, even if this means that motor was at stall, suitable fusing could be used in this instance to prevent damage to the motor.
    Max.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Rereading the OP, I'm a little confused. The way I read it, there are some circumstances under which the actuator DOES stop properly with the 150# load attached. Is this correct? If so, that indicates to me that it should be possible to stop the load without the added effort and cost of fitting a brake to it. I think that before you go that route, you should experiment with control schemes that short the motor leads when no directional command is given. You can play around with this without buying anything. with a 150# load attached, Hold the motor leads to a power supply until its going down, full steam ahead, then remove the leads and immediately short them together and see if it stops on a dime. Then report your findings and we will have a better idea how to proceed.
     
  7. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    Hi Strantor ....
    "Rereading the OP, I'm a little confused. The way I read it, there are some circumstances under which the actuator DOES stop properly with the 150# load attached. Is this correct? If so, that indicates to me that it should be possible to stop the load without the added effort and cost of fitting a brake to it."

    The motor "Brakes" in 2 cases, both of which are impractical:
    1 With the internal limit switches. The problem in this case is that the suspended load torques the suspension bar forward at the lower limit, distorting the bar and misaligning the internal limit switch with the internal tongue that actuates the limit switch. Result, the motor continues (off and on) to try and (over) run until an overload circuit kicks in and stops the motor. Solution would be to have a beefier suspension bar that would not distort (not an option). Hence, I decided to locate the switches externally so the suspension bar and the internal tongue is not in play. External switches also provide for limit switch adjustment.
    Although Firgelli rates the lift at 200# and I only have 150#, the internal limit switches are not reliable or adjustable due to the above. The Firgelli rating apparently is for the worm gear / drive rod combo and not for the suspension system.
    2 When using the RF remote. I am guessing that there is a circuit inside the remote receiver/power supply that does this. It is not realistic to use the remote to start / stop the load at the upper and lower limits as the push buttons do not always actuate. Also, I need to achieve as near as possible to full travel due to physical room limitations.
    and "Coasts" in this case:
    3 With the new external limit switches. This wiring, limit switches, and diodes are identical specs to the internal wiring, except for a small IC board (see attachment picture of limit switch in prior post). Is there something in that little board that shorts and therefore brakes the motor?

    "I think that before you go that route, you should experiment with control schemes that short the motor leads when no directional command is given. You can play around with this without buying anything. with a 150# load attached, Hold the motor leads to a power supply until its going down, full steam ahead, then remove the leads and immediately short them together and see if it stops on a dime. Then report your findings and we will have a better idea how to proceed."

    Unfortunately, that is not possible as the motor, worm drive, and motor wiring are all contained inside a motor housing shell. If this is disassembled, the worm drive will not connect to the spiral lifting rod. As to an external brake, there is not shaft area available at either end.

    I certainly willing to spend a few bucks to experiment for an alternate wiring design that would short the motor and cause braking. Is there a way to modify the external limit switch circuit I submitted to short the leads and reverse polarity?
     
  8. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    All your mechanical jargon is lost on me. a picture is worth a thousand words. A video is worth a thousand pictures. If a video is too much, then If you have a diagram that shows what all these parts are, that would be helpful. Or a labeled picture. If you have a manual for this thing, now would be the time to upload it.
     
  9. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    Strantor ....

    I have sent all the pictures and diagrams I have.
    The product is a Firgelli 60" Linear actuator. This link is for a 50" TV lift:
    http://www.firgelliauto.com/product_info.php?cPath=95&products_id=289
    The only manual Firgelli publishes is lift/actuator assembly instructions.
    The 60" actuator is the same as the 50" except 10" longer. The 60" linear actuator only is here:
    http://www.firgelliauto.com/product_info.php?cPath=123&products_id=291

    Frustrating I know - I am too. Very limited/nonexistant "support" from Firgelli.

    Bottom Line: The only option that will work is an external limit switch setup. That I have completed, except it coasts to a stop - and I need it to brake to a stop.

    Thanks for looking at the problem.
    I am still hoping somebody can help with a circuit that will do both.
     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    I'm having trouble understanding how things are wired up in each of the 3 scenarios. are your original limit switches wired in series with the motor? Are your new limit switches wired in series with the motor? Are there relays anywhere in the system? I'm a little confused by the plug on the gearbox case; it seems your wires from the limit switches could possibly go back to the power supply and perform some logic function there, instead of being in series with the motor.

    Rereading post #7, it sounds almost like an instant braked stop is too violent on the apparatus, even with external limit switches. Do you agree? Do you think that maybe the coast-to-stop option is actually better? Could you just move the external limits up by 3"?
     
  11. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    Strantor ....
    Thanks for your ongoing interest ....

    I'm having trouble understanding how things are wired up in each of the 3 scenarios. are your original limit switches wired in series with the motor? Are your new limit switches wired in series with the motor?
    Yes, all 3 conditions are wired the exactly the same, with the limit switches in series and factory orientation of the diodes. One concern is that "switch function" of the external SPDT microswitch I installed is "On,Mom". I would have thought it would be "On,Off" but it does seem to work. Any thought on that?

    Are there relays anywhere in the system?
    Not that I am aware of, however, I have not taken apart the remote control power supply - some may be there. The small R&B wires that have the limit switches wired in series go to a small circuit board in the motor head. Also possibly some there but not the 3/4" sq type as the board is basically flat on the device side. Wish I had taken a picture of that, but it would take 1 1/2 hours to take the actuator down and another 1 1/2 to put it back up.

    I'm a little confused by the plug on the gearbox case; it seems your wires from the limit switches could possibly go back to the power supply and perform some logic function there, instead of being in series with the motor.
    Yes likely, because the remote receiver is also in the power supply block and when the remote is used for stop/start the motor brakes. Problem is, I am not sure I could pull that off.

    Rereading post #7, it sounds almost like an instant braked stop is too violent on the apparatus, even with external limit switches. Do you agree? Do you think that maybe the coast-to-stop option is actually better? Could you just move the external limits up by 3"?
    I am slowly coming to that point of view. Not only easier on the motor, but also the motor worm/gear drive and the ball/screw drive. One of my friends suggested a physical stop (~3" below the limit switch) with moderate to firm resistance, such as medium density rubber/foam. Could that be the failsafe I need?

    A new development is that Firgelli sell a motor controller that - IF it fits my actuator - would slow the travel, and therefore the momentum, to 33% (.2 in/sec) of current travel speed of .6 in/sec. After looking online today, there apparently are also aftermarket controllers to consider, some with soft and/or brake stop in addition to speed control.

    THANKS AGAIN.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,534
    2,369
    That method of L.S. in series with the motor itself is a common down and dirty method of uni-direction control, once a limit switch is made, the diode only allows the motion in the opposite polarity/direction.
    I think as post #5 the cushioned physical O.T. stop would be advisable.
    You must have some way of removing power to the motor at this point as the current will be very high, either a fuse or a resettable breaker.
    The motor mentions 29vdc, is this an on/off controller?
    If you fit a controller that goes into slow, there would have to be an input of some kind to indicate the slow position reached?
    Max.
     
  13. mrstair

    Thread Starter New Member

    Sep 21, 2013
    6
    0
    Hi MaxHeadRoom ....
    That method of L.S. in series with the motor itself is a common down and dirty method of uni-direction control, once a limit switch is made, the diode only allows the motion in the opposite direction.
    Understand, do you think a "Momentary On" sufficient, or do I need a "Off, On" Limit switch.
    I think as post #5 the cushioned physical O.T. stop would be advisable.
    Agreed - I do need some form of failsafe - and a slower travel also seems a good idea.
    You must have some way of removing power to the motor at this point as the current will be very high, either a fuse or a resettable breaker.
    Where would the current read high (at the motor? 110 supply? and where would it be best to install a fuse/breaker? There is some kind of power supply overlimit kickout now, but it takes as much as 15sec to kick in (motor stops trying to run).
    The motor mentions 29vdc, is this an on/off controller?
    More like a up/down from the remote. The remote control receiver and the power supply are in one block.
    If you fit a controller that goes into slow, there would have to be an input of some kind to indicate the slow position reached?
    Not sure what you mean here .... Most of the controllers seem to have a rotary rheostat way to set speed, so once set, the speed would always be the same.

    THANKS for your ongoing interest ....
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,534
    2,369
    Most limit switches are Momentary, seldom maintained used in this context.
    I am just wondering what the nature and voltage is of the motor controller, is this a simple diode bridge type across the 120v?
    If this is this type, there are controllers on ebay etc that are made by KB and Baldor that have a SCR controlled bridge and can offer some kind of control other than the simple on/off, and also offer current limiting or shut down on a high preset current .
    A stalled DC motor with full voltage applied represents a virtual dead short on the supply unless the supply is reduced or removed, if O.L. or fuse, the protection would be best in series with the motor.
    Max.
     
Loading...