LiftMaster Door Operator

[synchro]

Is there anything that could be done to provide a little more kick to the startup? Like adding 1 capacitor in immediate series to each of the Red and Yellow inputs of the motor?

Your motor setup is a reversible permanent split capacitor arrangement like this where the two windings are symmetrical so that the same torque is available in either direction:



It's likely that you can increase the capacitor somewhat to increase both the starting and running torque as kwired mentioned:

“Hotrodding” AC Capacitor Motors and Gearmotors …At your own Risk

You can get higher starting torque from an AC induction motor by replacing factory specified capacitors with larger ones. But pushing the motor too far beyond design specs is risky. Here’s how ca…

gearmotorblog.wordpress.com

If you do this I'd limit the cap increase to 50% and see if that helps. This could be done by adding a capacitor in parallel that has half of the existing capacitance value.

Because adding more capacitance can increase the peak current draw, to avoid stressing the relays on the board it could be wise to add a pair of contactors/relays to drive the motor directly from the line. The coils on them would be driven by the relay outputs that drive the motor now. It's also possible that the existing relays are marginal for the current as it is, and so adding more robust contactors might help and extend the life of the door operator.

 

[synchro]

We are on a fulltime Tesla system and the voltage is pretty constant. I've put a Kill-O-Watt meter on the unit and during normal operation, the unit draws ~4.5 amps, voltage drops from 117 to 112 and slowly climbs up until the gate finishes its operation. When stalled, you can hear the relays click, you can hear the motor hum, the current draw is a ridiculous 8+amps, voltage drops to 103 or so, but the motor does not start turning. A healthy shove in the right direction sometimes gets it to roll. Whatcha think?

To get the amount of voltage drop vs. current that you're observing there'd have to be at least 1 ohm of total resistance. It would take nearly 400 ft of #14 (a 200 ft run) to get that much resistance. I would recommend tracking down where in the chain the voltage drops are occuring.

 

[caribconsult]

Physically in the unit, not certain. On your schematic you posted near bottom right of the page is two boxes representing them, one for open (OP) one for close (CL) each has two "coil" terminals and 9 terminals for power leads, or three sets of COM/NO/NC contacts.

Most commercial operators I have dealt with they are usually easily field replaceable definite purpose contactor style unit. Residential operators it may be more of a PCB relay, probably because the residential ones usually have smaller motors and the commercial ones are big enough the PCB relays won't have heavy enough contact rating.

Adding more capacitance would increase phase shift and give the motor more torque. Too much will smoke it, though on a short duty cycle like this has there is a lot of in between that gives more torque but still will eventually end up with shortening life of motor. But presuming nothing is wrong and you do need more torque then what you have is undersized for the task at hand. before messing with the capacitor I would want to know if both motor windings are drawing current when this thing is not working. If one is but other one is not - I'd still suspect open relay contact that is supposed to be closed. Capacitor isn't that prone to being something that intermittently works relay contact much more likely to be intermittent. I say this because you said the motor hums but won't turn. If nothing happened at all, not even brake release, then the issue probably more likely in the control circuit.

You asked about RPM sensor as well. It doesn't show details of it, just the terminals that interconnect to the control circuit, they are on lower left of the first image in the post with two images.

Good question about whether both windings are receiving power when it stalls. And it's developed a new trick, also very intermittent: it will be fully open, I hit the remote, it starts to roll closed, and after about 6' of movement it stops, dead. No hum from the motor. Pressing the remote will result in clicking noise inside the housing, but no motor action. A firm push and it will reverse itself and return to fully open. Another click on the remote and it closes fully. It has done this several times and I am calling in an authorized factory service tech to see this, and he better have some test equipment with him, because if I can get it to stop midstream again, this should be findable. The motor is not getting power any power and that should be something we can find. I'm starting to suspect a relay. I will keep you up to date, and thanks for your knowledge.

 

[caribconsult]

To get the amount of voltage drop vs. current that you're observing there'd have to be at least 1 ohm of total resistance. It would take nearly 400 ft of #14 (a 200 ft run) to get that much resistance. I would recommend tracking down where in the chain the voltage drops are occuring.

It is a rather long run, probably 150' altogether to the power panel but there was a time when it was connected with the same #14 wire right to the meter box, about a 70' run, and we had the same issues. And the run hasn't changed in over two years, so how does that account for the totally erratic behavior? If there was insufficient power, I'd think we'd see this much more frequently. I'm calling in a factory tech to examine this thing. Thanks for your input.

 

[caribconsult]

Your motor setup is a reversible permanent split capacitor arrangement like this where the two windings are symmetrical so that the same torque is available in either direction:

View attachment 2553059

It's likely that you can increase the capacitor somewhat to increase both the starting and running torque as kwired mentioned:

“Hotrodding” AC Capacitor Motors and Gearmotors …At your own Risk

You can get higher starting torque from an AC induction motor by replacing factory specified capacitors with larger ones. But pushing the motor too far beyond design specs is risky. Here’s how ca…

gearmotorblog.wordpress.com

If you do this I'd limit the cap increase to 50% and see if that helps. This could be done by adding a capacitor in parallel that has half of the existing capacitance value.

Because adding more capacitance can increase the peak current draw, to avoid stressing the relays on the board it could be wise to add a pair of contactors/relays to drive the motor directly from the line. The coils on them would be driven by the relay outputs that drive the motor now. It's also possible that the existing relays are marginal for the current as it is, and so adding more robust contactors might help and extend the life of the door operator.

I've got the concept. The RC circuit induces a phase shift in one coil while the other coil is connected directly and the lag produces rotation of the armature. Switch coils and the motor reverses. That's exactly it. So I don't have to change the 2 ohm resistor? Right now it has 40µf cap, so I could just add another 20µf in parallel to the existing? It's worth a try. I can get these caps at a local electronics supply store. I'm going to have to consider that. Thanks for the tip and let me know about the resistor, please? Thanks mucho.

 

[McLintock]

Y’all are making this too complicated, I have installed many of the liftmaster MT, MJ, M, J models, 95% of the time with enteric/intermittent problems it’s the logic broad, that’s what control them anymore, or you open/close nuts might not be locked in at all and moving freely, seen that a couple of times too. But it is not a electrical problem


“ shoot low boys their riding shetland ponies”

 

[caribconsult]

I must be missing something. I've looked thoroughly through every component in my MJ5011 and I don't see anything resembling a PC board...is that what the logic board is? There are relays, a small transformer, lots of wires, the RC components, and a large terminal block and the assembly that determines the open and closed position with positioning nuts. Nothing appears abnormal. The positioning nuts are not drifting around and gate, when it runs right, goes consistently to the designated close and open positions. Where is this logic board? There is a PC board int the receiver for the remote but I don't think that's what you are talking about. Some more explanation, please? I've been told by LiftMaster TechSupt that I don't have the 'logic' model, it's just an MT. Some clarification would really help. Thanks for contributing.

 

[McLintock]

I must be missing something. I've looked thoroughly through every component in my MJ5011 and I don't see anything resembling a PC board...is that what the logic board is? There are relays, a small transformer, lots of wires, the RC components, and a large terminal block and the assembly that determines the open and closed position with positioning nuts. Nothing appears abnormal. The positioning nuts are not drifting around and gate, when it runs right, goes consistently to the designated close and open positions. Where is this logic board? There is a PC board int the receiver for the remote but I don't think that's what you are talking about. Some more explanation, please? I've been told by LiftMaster TechSupt that I don't have the 'logic' model, it's just an MT. Some clarification would really help. Thanks for contributing.

You must have a older one? How old is it? Can you upload a pic. with the cover off?


“ shoot low boys their riding shetland ponies”

 

[caribconsult]

You must have a older one? How old is it? Can you upload a pic. with the cover off?


“ shoot low boys their riding shetland ponies”

The label on the chassis says date of mfg Feb 18, 2919, its barely a year old. I'll try to get you picture with box lid open

 

[caribconsult]

You must have a older one? How old is it? Can you upload a pic. with the cover off?


“ shoot low boys their riding shetland ponies”

A few pix showing insides and mfg label. As you can see from the shine on the clutch and the lack of wear on the drive belt, as well as the mfg label, this is a fairly recent mfg. Do you see a logic board?

 

[caribconsult]

I think there may be two separate issues going on here. The 'stall' and failure to start turning at the beginning of a cycle is one issue. The motor hums, it is getting power, but won't turn. The situation where it begins to close then stops dead about 1/3 of the way closed is something else entirely....here, the gate is rolling and stops dead, no hum to the motor, receiver responds to remote but no gate movement. No power to motor. Something else has disconnected or some switch has been tripped accidentally. Two different symptoms, I believe. Your thoughts? Always welcome, thanks.

 

[kwired]

A few pix showing insides and mfg label. As you can see from the shine on the clutch and the lack of wear on the drive belt, as well as the mfg label, this is a fairly recent mfg. Do you see a logic board?

That is "old school" design. I suppose they still do make them but never have seen one in a new installation in 10-15 years now that didn't have the PCB main board, remote control receiver is built into the main board on these newer units. Most don't even have the adjustable stop limits anymore they detect how far travel was and stops are electronically set in the board.

 

[McLintock]

Something is fishy here, liftmaster as used logic broads for years, 15 at least, the date and the unit does not add up to me at all. I would have just put a new one in with a broad in it.


“ shoot low boys their riding shetland ponies”

 

[caribconsult]

That is "old school" design. I suppose they still do make them but never have seen one in a new installation in 10-15 years now that didn't have the PCB main board, remote control receiver is built into the main board on these newer units. Most don't even have the adjustable stop limits anymore they detect how far travel was and stops are electronically set in the board.

I hear you. This is local engineering at its finest. This unit, never intended for a rolling gate, is everywhere down here, probably at least half if not more of the rolling gates I've seen, a very common part of a home if you have room for it. It's identical in layout to the one we had installed when we first moved here in 2003, and which lasted about 12-13 years before it began acting up and stalling. The local installers claim it works well, which I suppose it does or they would have found something else in the meantime. I'm going to experiment with adding just a bit (20µF) of capacitance, per the suggestion of another poster here, to see if that cures anything. I will let everyone know the results.

 

[caribconsult]

Something is fishy here, liftmaster as used logic broads for years, 15 at least, the date and the unit does not add up to me at all. I would have just put a new one in with a broad in it.


“ shoot low boys their riding shetland ponies”

I hear you. All I can say is what I replied to KWired - this is local engineering at its finest. This unit, never intended for a rolling gate, is everywhere down here, probably in at least half if not more of the rolling gates I've seen, a very common part of a home if you have room for it. It's identical in layout to the one we had installed when we first moved here in 2003, and which lasted about 12-13 years before it began acting up and stalling. The local installers claim it works well, which I suppose it does or they would have found something else in the meantime. I'm going to experiment with adding just a bit (20µF) of capacitance, per the suggestion of another poster (Synchro) here, to see if that cures anything. I will let everyone know the results. I also have an appointment for a Liftmaster tech to come by on Aug 13, and I asked them to please send their #1 guy with test gear, not some freshman who will look at it and say "Dude, it's not running right." Results will be posted.

 

[kwired]

Something is fishy here, liftmaster as used logic broads for years, 15 at least, the date and the unit does not add up to me at all. I would have just put a new one in with a broad in it.


“ shoot low boys their riding shetland ponies”

I don't know what they offer, and keep in mind this is in Puerto Rico and they may market different product line there, but it wouldn't surprise me if that old style unit is still made, just not sold and/or no retailers or other higher volume purchasers are requesting them so they are rare to non existent in the US. I know I haven't seen a new one of that design for 10-15 years myself.

 

[McLintock]

If you look at the closely and the MFG date the 9 is different than the 9 on the serial number, I bet they “rebuilt” one and sold it


“ shoot low boys their riding shetland ponies”

 

[hillbilly1]

I'm pretty sure thats the same model Home Depot uses on their roll up doors, though I haven't worked on one for them in years, I don't remember a pc board on them. They probably still make that model that is sold in countries with bad utility power because electromechanical holds up so much better than electronics in those cases. I would still say its a brake issue, but since it did it with the old as well as the new one.........If its the brake assembly I'm thinking of, the solenoid when de-energized, pops into a hole on a disc. Perhaps the disc is warped, and/or sometimes the plunger is not fully retracting? Might be something to check.

 

[caribconsult]

I'm pretty sure thats the same model Home Depot uses on their roll up doors, though I haven't worked on one for them in years, I don't remember a pc board on them. They probably still make that model that is sold in countries with bad utility power because electromechanical holds up so much better than electronics in those cases. I would still say its a brake issue, but since it did it with the old as well as the new one.........If its the brake assembly I'm thinking of, the solenoid when de-energized, pops into a hole on a disc. Perhaps the disc is warped, and/or sometimes the plunger is not fully retracting? Might be something to check.

Much of what you say about our electric grid is true, and this unit, being more mechanical than electronic, probably stands up to the vicissitudes of the grid here. We went full Tesla 2 years ago and the problems continue. All the mechanical parts - clutch, brake, solenoid, etc. seem to be functioning. The stalling situation seems to have backed off and now the screw up is that it will just stop dead in the middle of closing. This should be a lot easier to track. I have a Liftmaster tech coming in 10 days and if we can get the unit to stop dead he should be able to find where it went off the rails. Wish us luck, that we can get the gate to do this while he's here.

 

[caribconsult]

I don't know what they offer, and keep in mind this is in Puerto Rico and they may market different product line there, but it wouldn't surprise me if that old style unit is still made, just not sold and/or no retailers or other higher volume purchasers are requesting them so they are rare to non existent in the US. I know I haven't seen a new one of that design for 10-15 years myself.

You're probably right about that. This unit is everywhere down here, and as you point out it might have been re-manufactured a year ago, not entirely new. There's not a whole lot we can do about it, since all the dealers feature this unit.