On the windscreen wiper motor.

Is it generally a simple case of polarity changing to switch direction? Or is it a little more complicated?

Depends on the motor (generally: permanent magnets, no. electromagnets, yes), but probably easier just to use a linkage to reverse direction. That way for half the time the door is opening and half the time it's closing, but the motor runs constantly in the same direction.

The motor will fail, and you will be trapped up there, your muffled shouts drowned out by the tv and traffic.

After a week of missing posters on shop windows and telephone poles, and cops scouring the neighborhood, it will be assumed you ran off, or just got offed.

Years later, your dried husk will be found with broken fingernails and deep scratches in the hatch, after your family moves away.

Or, you can stop right now.

I still don't understand :((

So let's say I was to apply a voltage to the relevant wires it wouldn't turn 360 deg continuously? It would go, say, 180 deg and back again?

I just want a simple motor I can turn 360 for a set amount of time, then -360 deg.

Also, my hall effect sensors arrived, but I forgot to order magnets. I've had so much stuff from China arrive in less than 2 weeks recently. One item in 7 days too.

I think I'll fit an emergency axe in the attic.

https://youtu.be/D_KIOr_TpcM

Thank you :$

It's done like that because rapidly switching the direction on a motor (like windscreen wipers would have to) is really not nice for the motor, especially when there's a biggish load on the motor.

Makes total sense, and I quite like that video. I could probably get one for a fiver at the scrap yard or 7 quid buy it now on ebay. I think I'll buy one and have a play.

Worst case scenario you have a relatively small, relatively high torque motor. That'll definitely find itself another use if it's not suitable for the door thing.

Discovered you can make a H Bridge using two relays. I happen to have a 2xRelay module which is now working as a H Bridge. Really really simple to use. If the relays are the same (high/low) the motor would be off. Set one relay high to turn the motor, swap which is high to change direction.

Eg
L/L & H/H - Off
L/H - Forward
H/L - Backwards

Super dull video

Arduino, 433 MHz receiver, relay module and hall effect sensor.

The idea is to have the motor running for x seconds, but if the hall effect sensor is triggered it stops. A bit of a fail safe to stop the motor in case it is already fully open.

Erm, I shouldn't have bought a rear wiper motor. Back to ebay (or hack this apart).

That's better. Ford Focus front wiper motor.

It's got quite a kick to it.

Your vid is private :(

Should work now.

Haha - they've got some real torque haven't they!

Bloody hell, it actually works.

Need to add the magnets/hall sensors - edit: added one for opening, works well.
Change the open/shut duration,
Support the upright better,
Possibly switch the side of the motor because it is slower in one direction compared to the other. I'd rather the closing direction be slower and more controlled.
Add some flyback diodes.

Used the an Arduino app on Android for the first time the other day "ArduinoDroid". Not the best app but still really useful. Saves disconnecting everything or bringing a laptop into the attic to tweak the sketch.

Current progress. Not finished, still waiting for magnets to arrive so I can finish off and paint, but working nicely.