Monitoring shade poistion with "dumb" motor

I've got a patio shade (big) that I'm powering with a power window motor. I'm trying to figure out ways to automate it, but because it's just a "dumb" motor, I need to come up with a system of letting arduino know the shades relative position.

The basics. Currently there is no Arduino. The motor is powered by two relays and two NO pushbutton switches. Push one button, the shade goes up. Push the other, current is reversed and shade goes down. I like this circuit, because I can power the motor "manually" with a 3 cell lipo and the voltage is isolated from the future Arduino circuit (I may use a UBEC to power the Adruino from the same battery). My plan is to tie the Arduino to two relays that can momentarily close the pushbutton switches (up/down).

Again, the problem is the Arduino has no idea what the position of the shade is, so I'm just looking for some ideas. Here are mine so far...

micro switch positioned either on top or bottom where shade base passes.

IR transmitter/receiver positioned either on top or bottom where shade passes.

Ultrasonic sensor (I like this cause I have one, although it seems overkill).

and was also wondering if it was possible for Arduino to monitor current to shade motor - as shade get's heavier (moving up), current/resistance of motor must increase, so this could also be a way to determine shade position.

Obviously a stepper motor would be better, but the power window motor, which is geared works great.

Anyhow, any other thoughts would be great.

Thanks in advance!

I like the simplicity of microswitches.

Will the shade always be either fully in or fully out - which is the simplest situation?

...R

I like the micro switch, but would have to attach something to the shade to trigger it, which I dislike. I'm also worried about the possibility of the shade getting snagged on something and the micro not triggering, say if someone puts something near the shade without knowing that it's automated.

My plan before moving the shade to a specific position is to "calibrate." In other words, once I can determine when the shade is either full up, or full down, I'll just run motor for "x" seconds in either direction to put it where I want (ultimately tied to a temperature sensor).

Hi,

Look up magnetic reed switches like the one used in security systems for window switches.
They are weather proof and non contact.

Hope this helps… Tom… :slight_smile:

Depending on the motor you have and the shade system you can passably monitor motor current only.

This is done on some radio towers I have worked on. The motors will draw X during normal operation and if draw exceeds a set limit the operation will stop and ask for human input. This is done since cables can get snagged, or in nasty weather ice loading can also become a problem. Limit switches will not catch either problem. The tower also has limit switches (proximity sensors, no moving parts) but in theory would be able to run without them since it will stall at the end of each cycle.

If your motor has a very high gear ratio the set points are harder since you will have more force applied with a smaller relative rise in current.

Post a photo or diagram so we can see how the shade works.

...R

It seems that if switches only are used a potential situation encountered would be if no switches are activated. Where is the shade? I suppose in that situation the motor could be driven until a switch is activated, giving the system a known position. The desired requirements of this system seem analogous to the system used in automotive power windows. You may want to look into that to see if you may be able to adapt components and logic used there for your project. - Scotty

The push button circuit I'm using comes from a power window schematic. With power windows though, you have something that stops the window when you are full up or down - the window frame. My shade has no such restriction - so I think I'm leaning away monitoring the current as a limit.

I like the reed switch option - one would be light enough to attach to the shade but shade moves a bit with ceiling fan on, so again, I'm worried about that rare moment when contact isn't made.

So, I'm going with ultrasonic range finder for now. Doesn't require any additional hardware and I've got one.

Since it was asked - because I it is possible to use pushbutton switches between automated events, I'll plan on calibrating (moving to full down) before any event. Not exactly high tech, but hey, a shade moving on it's own is kinda cool anyhow.

Thanks for the inputs!

btw: I took some photos, but can't seem to input them - user error/ignorance I'm sure.