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[General] How does a garage door opener sense the open/close force with a microcontroller?

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userx2

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Hi
I found this interesting and wonder if anyone knows the answer?

I have here a garage door controller that uses a PIC 16 series microcontroller.

The board has inputs for upper and lower endstops (switches).
In addition, there is an optical sensor that has a spinning disc going through it which sits on the motor shaft.

The motor control is a simple relay control. No speed control, no current sensing, nothing else.

That's it.

There are potentiometers for adjusting the opening and closing force thresholds.

Basically the motor stops when the set force is exceeded.

My question is: Given that there is only a speed sensor (disc), how on earth does the controller figure out the force?

Regards
X
 

Perhaps it senses current draw. Suppose the door stops as it hits an obstruction. The stalled motor draws greater current. (It is typical behavior of motors).

I would imagine a clutch is in there somewhere, to absorb some of the abrupt action between motor and door.
 

BradtheRad said:
Perhaps it senses current draw. Suppose the door stops as it hits an obstruction. The stalled motor draws greater current. (It is typical behavior of motors).

I would imagine a clutch is in there somewhere, to absorb some of the abrupt action between motor and door.
Click to expand...

As mentioned, there is no method for measuring any current. If there was, I would not be wondering...

Regards
X
 

What makes you think the microcontroller can sense the open close force.
 

Although it is natural to think the spinning disk provides a means of measuring, I was not ready to suggest it indicates force. Force is not directly measured by the spin rate.

However the writer of the instructions may have wanted to make it easy on himself and the homeowner. So he described the function so it 'sounds plausible'. It may not be technically correct, but it is easy to grasp.
 

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    userx2

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rangermad said:
"Motor deceleration is also monitored for obstruction detection"

https://www.google.com/patents/US5278480
Click to expand...

That patent is very interesting and I think that what I have here operates very much as described.

One requirement for this is that the motor is weak enough to decelerate quickly upon contacting an obstacle.

The kW motors and controls I typically deal with would not notice this before destruction.

I still think it is clever.

Regards
X
 

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