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Mike2

Latching Device

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I have a motor that pulls out a car sun shade, however once it is pulled down I need it to latch onto a hook or something to hold it down, and then the motor can shut off saving on power.

The problem is getting the latch/hook to fold down to allow the shade to roll back up, there shouldn't be any manual use so it would be done electronically, any ideas though on how to do it?

Thanks Mike

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I was looking at using something like this: http://auto.howstuffworks.com/power-door-lock3.htm

Though I was unsure on how it works with the motor, how does the motor know when to stop turning, does a current stop going tot he motor?

Could this work?

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The clutch mentioned is only to protect the motor from stalling when the actuator reaches the end of its travel. Typically, the door lock is done by time from an alarm or body control or even your finger. If you kept power on the door lock all the time it would eventually fail. Tell us more on how your shade works.

Do you manually roll it down (like a window)?

Do you use fishing string on a loop that pulls it down with your motor?

Do you have a motor that directly drives the shade?

There are a bunch of different ways to solve the problem do you want a latch is there a way to use a brake on the motor so that when you apply power to the motor the brake turns off and vice versa?

Jeff

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Thanks for your responses.

I will be using a roller shade / blind type device pulling it out horizontally. I want to use a motor to pull the shade out, once pulled out I want the motor to stop, and the shade is held in place. This is done by turning it on. Turning it off, or the switch the other way, the shade is pulled back and rolled up using a or the same motor.

This is an image to show what I mean: scan10001rd6.th.jpg

I want it to be all automatic, all the users does is flick a switch. I was going to use fishing string for it. the motor I am currently using to test is a simple motor which rotates in either direction depending on how the positive and negatives are connected, it doesn't have self-inhibited gear, so it can be rotated with out power manually.

Do I need two motors to make it pull out and roll up? How can I make it switch off when the shade is puled out upto the pulley (The shade can be set to work with different lengths, eg how far it comes out)?

Thanks

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A spring loaded rollershade will probably rotate the motor backwards by pulling the fishing string once it has been pulled out and the power is removed from the motor.
I believe you need some sort of brake to hold the motor while it

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A spring loaded rollershade will probably rotate the motor backwards by pulling the fishing string once it has been pulled out and the power is removed from the motor.
I believe you need some sort of brake to hold the motor while it

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Hmmm Ok, the problem is when the shade is pulled out, a pulley on the motor will be wound up with fishing wire, now then when I want to roll the shade up, the motor will have to pull the shade back, as well as pulling against the force of the other motor to unwind it? Is there another way to do it?

Also whats the best way to shut off power to the motors once the shade has been pulled out as far as needed, or rolled up? I was thinking something like a push to break switch, however once the shade goes back and releases the push to break switch it may cause some problems...?

Sorry for all the questions, but I'm a bit of a novice with electronics and having problems imagining how it would work.

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There is no problem to use one motor to pull another motor backwards and vice versa as long as only one at the time is powered.
One way to set up a circuit is with two latching relays and two micro switches one for each direction.

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Ok, I have worked out how it will work and the simple circuit it will run off, will the Micro Switch be used as the push to break trigger for when the shade has been pulled out?

I have sourced them here, though am unsure if they are the correct ones from the choice, which ones should I have picked?

Latching Relay:  http://www.maplin.co.uk/module.aspx?ModuleNo=37529&doy=5m3#overview
Micro Switch:   http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=6452&doy=5m3

I am looking at running the circuit off 3V, and may incorporate an IR remote. (Ambitious I know)

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I would probably use shades instead which just needs to be tipped not rolled out. This I would then be controlled by an RC servo (PWM).

Edit: should be BLINDS not shades! sorry for the mixup!

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O, well if you know anything about relays, or latching relays, please help me out in this thread

http://www.electronics-lab.com/forum/index.php?topic=10551.msg57939;boardseen#new

Thanks.

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I would suggest using a motor with a worm gear. This way you only have to use one motor and there are no relays to deal with.

worm-gears.jpg

When a motor is geared like this it has a slow rotation, but a large amount of torque. The only way to make the round gear turn is by turning the work gear, the round gear can not turn the worm gear. 

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