# slowing down speed on garage door opener

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#### diy549

##### New Member
Hello,
I'm new to the forum and I have a question for you all. I am building a bed that slides up into a wall, the bed slides on guided tracks into a vertical position. I am done with the construction side of it and its working perfectly. Now, I need help with the electrical side of it. To make things simple, I figured I would use a garage door opener because the bed basically works like a garage door. The problem is garage door openers travel about 7 inches per second and thats too fast for comfort. I want it travel about 2-3 inches per second and this where I'm stuck. If you guys could tell me what I need to make this happen it would be great. I'm assuming I cant just throw a speed controller in there. I was thinking I should go with a older model because the are a lot less complicated as far as the electronics.

Thanks guys and gals

#### dknguyen

##### Well-Known Member
What type of motor is it using? The electronics are dictated by the kind of motor and AC motors tend to require the most complex electronics for any kind of speed control (or even reduce speed). With most DC motors you can usually just reduce the voltage and the motor runs slower. With most AC motors you have to change the frequency and voltage- neither of which is easy since they both require extensive manipulation of the AC waveform. And with constant speed device where speed accuracy isn't really even important like a garage door opener, I doubt there is any form of speed control electronics at all. THey probably used gearing and knowing what the power supply is (120VAC mains) they know the approximate speed it will run at.

So... you could do what they do and try to gear the motor down (that's what I would try and do first before messing around with electronics). THat's the most effective method since you get to sidestep all the electronics as well as the strange AC motor performance curves and you don't waste any of the motor's power capability. Rather than running it at a lower power (lower speed AND torque), you are taking the excess speed and turning it to torque so the motor is not working as hard and actually runs cooler.

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#### diy549

##### New Member
What type of motor is it using? The electronics are dictated by the kind of motor and AC motors tend to require the most complex electronics for any kind of speed control (or even reduce speed). With most DC motors you can usually just reduce the voltage and the motor runs slower. With most AC motors you have to change the frequency and voltage- neither of which is easy since they both require extensive manipulation of the AC waveform. And with constant speed device where speed accuracy isn't really even important like a garage door opener, I doubt there is any form of speed control electronics at all. THey probably used gearing and knowing what the power supply is (120VAC mains) they know the approximate speed it will run at.

So... you could do what they do and try to gear the motor down (that's what I would try and do first before messing around with electronics). THat's the most effective method since you get to sidestep all the electronics as well as the strange AC motor performance curves and you don't waste any of the motor's power capability. Rather than running it at a lower power (lower speed AND torque), you are taking the excess speed and turning it to torque so the motor is not working as hard and actually runs cooler.
That was my first thought, but the pulley on the motor is specific to the manufacturer, I could go with a chain opener, then it would be a matter of mounting a bigger sprocket on the existing one. But the chain is a lot louder than the belt route. If I go the electrical route with a 24vdc motor do you think the opener would have some kind of safety switch preventing me from droping the voltage. The bed is very light, a lot light than any garage door, so I don't think I would have a problem with power. What would I use to drop the voltage?

#### dknguyen

##### Well-Known Member
I can't say about the safety for dropping of the voltage. It depends on how much of the electronics in the garage door opener are actually involved in moving the motor. If it's just a relay, no.

Of course, you would also have to find a way to get 24VDC, and to power the rest of the garage door opener from that too (or use AC and DC to power it).

#### diy549

##### New Member
Of course, you would also have to find a way to get 24VDC, and to power the rest of the garage door opener from that too (or use AC and DC to power it).
I confused here, I'm not quite sure what you mean. Why would I have to find a way to get 24vdc? If the garage opener operates off a 24vdc motor, isn't the power already there. I just need to drop it, right?

#### birdman0_o

##### Active Member
What I would suggest is buying a wench motor and hooking that up somehow; they have very low RPM and high torque. However you would need to find your own way to regulate that down to 12-24VDC.

I would be scared that with a garage motor that is designed for a heavy garage door, your bed might get overpowered and break.

Yes you would need to drop the mains AC voltage to the 24V needed ( Or it is already included in the box and you just need to plug it in to the wall)

Mike

#### kchriste

##### New Member
Forum Supporter
I don't see why the existing motor would be anything other than a 120VAC one. You could possibly replace the motor with one that turns at a lower RPM but finding a reversing AC motor that would fit/work would be a challenge.
What type of motor does it have? This will determine how it can be speed controlled.

#### diy549

##### New Member
I would be scared that with a garage motor that is designed for a heavy garage door, your bed might get overpowered and break.

Mike
Yeah It does kind of scare me.
I don't see why the existing motor would be anything other than a 120VAC one. You could possibly replace the motor with one that turns at a lower RPM but finding a reversing AC motor that would fit/work would be a challenge.
What type of motor does it have? This will determine how it can be speed controlled.
I haven't bought one yet, but they come in AC and 24vDC, I figured I would ask you guys before I went out to buy one.

Thanks

#### Mike_2545

##### Super Moderator
I still want to see a video...

#### colin55

##### Well-Known Member
1. The first thing to do is find out the type of motor used in garage door openers and find out the cost.
The speed of opening a garage door depends on the diameter of the take-up spool. You need to know the RPM of the output of the opener.

2. Find out the cost of a gate opener. A linear actuator. Some of these are 12v or 24v.

#### diy549

##### New Member
I still want to see a video...
lol, I will once I get this figured out...
1. The first thing to do is find out the type of motor used in garage door openers and find out the cost.
The speed of opening a garage door depends on the diameter of the take-up spool. You need to know the RPM of the output of the opener.

2. Find out the cost of a gate opener. A linear actuator. Some of these are 12v or 24v.

#### 3v0

##### Coop Build Coordinator
Forum Supporter
When I look at this thing I see a human sized trash compactor. (sorry)
Buy a screw drive unit and put a gear reduction on the output shaft.
I should be more clear.

Buy a screw drive garage door opener.

Put a 2:1 or 3:1 speed reducer (surplus) between the motor and the long screw that drives the door.

You now have a garage door opener that moves at 1/2 or 1/3 normal speed and 2 or 3 times the torque.

You are going to need it to move that mattress around a curve.

#### MrAl

##### Well-Known Member
Hi,

Motors vary quite a bit actually, made for dc or ac.

For example, there are at least two types of AC motor: those with brushes
and those without brushes. The important thing here is that those with
brushes can be controlled using a triac while those without brushes can not.

A DC motor can be controlled using PWM.

Another option, as a last resort, is to try pulsing the motor at a very very
low rate...like once every second...so that the object (bed) appears to move
more slowly.

If you do end up with a brush type motor that runs on AC then you might
get away with the triac control by reducing the firing angle (same principle
that lamp dimmers work on). This also reduces the torque so speed/torgue

The best way is to gear it down somehow, but i guess that isnt an option here.
I know it is sure harder to do this because all the parts have to fit just right.

Just curious, did you try connecting a large light bulb in series with the motor
(assuming the one you have now is AC)? If the size is right you will reduce the
motor voltage and the starting torque may still be high because of the nonlinearity
of the bulb. Since it doesnt have to run long this should not bother the motor
too much either. If you can not get say a 100watt light bulb to work with it
then try 2 100 watt light bulbs in parallel, then 3, then 4, etc. Just might work
if everything else seems too expensive. The more light bulbs in parallel the faster
the motor turns.

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#### Mike_2545

##### Super Moderator
You are forgetting the friction of the mattress pushing up in the cavity. Any garage door opener with a gear reduction will have twice the torque, but also has the potential for being dangerous.

You should think about a Murphy bed design

#### dougy83

##### Well-Known Member
When I look at this thing I see a human sized trash compactor. (sorry)
diy549 said:
The problem is garage door openers travel about 7 inches per second and thats too fast for comfort. I want it travel about 2-3 inches per second
Because getting slowly crushed to death is obviously preferrable.

#### diy549

##### New Member
You should think about a Murphy bed design

OUT OF THE QUESTION

Because getting slowly crushed to death is obviously preferrable.
When I look at this thing I see a human sized trash compactor. (sorry)

.
As far as getting crushed, I built this bed with that in mind. the cavity is built so the bed is the only thing thats able to get through. The head board is connected by hinges at the bottom and magnets towards the top. If the the two switches were to fail and the motor came on and I happened to be asleep:1: I cannot be sucked up because of theres no where for me to go. 2: my headboard will release, 3: its moving only 2 inches per second, 4: I'm single, so I don't have to worry about anyone turning it on. I appreciate the help and sarcasm, but I have the safety part covered.

With that in mind, if I build my own system, I will add momentary switches under the mattress.

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#### MrAl

##### Well-Known Member
Did you try the light bulbs yet?

#### diy549

##### New Member
Did you try the light bulbs yet?
no I did not. I don't have the actual opener yet. I wanted to get some input first. I was going to get a belt drive, AC opener yesterday, but after reading through this thread, I think I will get a chain drive DC opener. And thats why I didn't want to just go out and buy one.

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