There is a space where I was thinking of putting the pj that is in a cabinet. I could take the door off the front but then it would look weird-like seeing someone smile to reveal a missing tooth. I would like to have a little motor swing the cabinet door open and shut it when the pj goes on and off respectively. The closest thing i can find are the electric gate openers made by Bulldog but that is overkill. Those devices are for moving things that weigh hundreds of pounds.

I was contemplating an IR controlled device or even something that is controlled by a contact switch. I dont want a garage door opener. just something small. Trouble is, i dont know how to go about searching for such a thing. Has anyone here done this? I sounds like it's something i should be able to make with lego mindstorms but i'd rather keep it simple. If it's already been done, I'd rather not reinvent the wheel.

Tnx.

Depending on the size and weight of the door you could utilize a RC servo to open it.
Search around robotics websites. Youll find what you want there :)

thing about servos is that one needs a complicated system to control them. I just need 2 states-open and closed. I do not need digital proportional control or even intermediate positions. the simplest thing i could imagine is a small hobby motor whose axle is fixed to a long threaded rod. A nut on the rod is then attached to a lever arm that is attached to the cabinet door. As the motor spins one way, the threaded rod is basically a worm gear that moves the nut and therefore the atached door. Trouble is, I dont really know how to wire contact switches to limit the excusion. If a contact is made, how then is that used to INTERRUPT a circuit?

The simple control I have imagined is two pair of switches - of the kind used to control a 'three way light switch'. one switch is activated by a relay from the controller(preamp trigger?). the motor runs and when the limit of the excursion is reached, the second three way switch is flipped, shutting off the circuit. Another pair of three way switches would be used for the opposite direction. But can you imagine mounting bulky three way switches just to control a little motor. there has to be an easier way.

Do a search on “electric linear actuator” in Google etc.

They are common machine design devices that do just what you described above. They come AC or DC and can be controlled with a couple limit switches and a couple push buttons etc.

You might find something here.

http://www.surpluscenter.com/sort.asp?UID=2007041015090085&catname=electric&keyword=EALA

tnx . linear actuator - never would have guessed that's what i was looking for. this is why google will never replace humanity.

Perhaps this easy for everyone else but so how do you do it? How do you take the Line Actuator and incorporate that into a door to make open and close automatically? Would anyone be willing share their instructions.

Karos-
If you want to PM me with your requirements, I may have a cost-effective solution for you.

Don

tnx for your help. I have sent for that actuator from surplus center. should be here any day now. I've built a control box with 2 outlets controlled by a relay. When a switch is thrown, the relay is closed and turns on one outlet. When the switch is turned the other way, the relay is open and turns on the other outlet. The actuator specs call for 2 120v ac sources-one is for 'open' and the other is for 'close'. This way I can wire the actuator with 2 plugs that run to the control box in a closet.

I assume the actuator knows when to stop. The specs refer to a 'hall effect' sensor. I hope I dont have to use that to sense when to stop the motor-it would complicate things.

I don’t know what actuator you bought but most need a stop signal. In most cases you wouldn’t use all the stroke they provide. Some do have overload clutching at the hard end of stroke. But that is more of a safety feature.

The common way they are used is with a forward and reverse pushbutton or rocker switch that is momentary contact. Pushing the button picks up a relay that locks itself up and also turns the motor on in the right direction. The motion is stopped ether when you hit a stop button or the travel trips a limit switch that opens the coil of the holding relay.

There are a 100 high tech ways to do this but this is the old way and the simplest with parts you could find at radio shack.

As to the above request as to how to rig something like this maybe karos will post some pictures when he gets it going.

If you need any more help on how a circuit like I just described works just ask. I can post something or find link showing something similar.

Hello,

I am hoping someone could help me figure this out. I'd like to use an actuator to open and close a small grill (weighing less than 2lbs). I'd like to hook this up to a projector that i have inside a wall. The purpose is to hide the projector when it is not in use. When the projector turns on i'd like the flap to open..then close when the projector is off. I have no idea where to start. I've attached a diagram of what i have currently. I need to know what to purchase and how to make it work with the projector. The projector is in the wall and is not easily reachable. I use a logitech harmony remote to control it. I'm not sure how to wire whatever mechanism i get to make it open when the projector is on. Any guidance is appreciated. THanks.

-Ross
ross@lawnranger.net

Hi RossLwn,

If you projector has a 12v trigger out, probably the easiest way would be to build a relay driver circuit that would operate a double pole double throw relay ( or 2 single pole double throw relays ). You would connect the common poles of the relay(s) to the actuator, and wire the power supply for actuator one way on the normally open side, and the other way on the normally closed side of the relay(s).

If you don't have electronics experience, a kit like this would probably work for you.

http://www.electronickits.com/kit/complete/elec/ck1619.htm

If your projector doesn't have trigger out, there are also IR controlled relay kits available. You could learn the IR codes into your Harmony.

Jonathan