reversable motor for monitor?

more mods · 09-09-2004, 11:04 PM

Can anyone help me with a schematic to make a DC motor move my monitor out when the ign. is on and back when the ign. is off. I think that this could be done with relays and micro switches, however I'm not sure about how to reverse the polarity to make the motor run in reverse. I would also need a way to override the position, if someone was with me I could close it so that they would have a good view angle, or if I wanted to use it with the ign. off and monitor open.

Help on any part of this would be great!

Here's what it looks like closed.

And this is open.

Quattro · 09-09-2004, 11:28 PM

Very nice idea, let me know how things turn out. I too need schematic for a similar thing I'm doing with my screen.

more mods · 09-10-2004, 01:53 AM

This looks like it might get me a little closer to what I want to do.
It will reverse the polarity, However I cant find a U.S. supplier.

Found here http://www.distel.co.uk/asps/details1.asp?ID=LE11

mushin · 09-10-2004, 03:43 AM

That looks like a straightforward DPDT (dual position dual terminal) relay. You can find those just about anywhere. Try radioshack, mouser, digikey, etc.

I'm still learning alot about electronics myself, so I'm afraid I'm not going to be able to whip out a schematic that does what you want, but here's some thoughts to consider:

You're either going to want a timer circuit or some shutoff switch so that the motors stop after the requisite amount of motion. The really schmancy way of doing it would be to detect the current spike when the motor stalls and shut it off then. That's how window auto-downs generally work, I believe. I have no idea how involved this would be. A timer would simply be set up to juice the motors for x amount of time. This can be done pretty easily with a 555 timer chip, which is probably the way I'd go (if only because I know how.)

Now you want it to change polarity depending on whether your ign went high or low. That relay would do it for you, but that alone is not an ideal solution because the relay would consume some power all the while you're driving. A solution here might be to use a transistor to only allow the ign current through during the duration of the motor movement, covered above.

Then there's actually telling the whole thing to go. You want a circuit that goes high when the ign makes a low->high or high->low transition. I think a flip-flop chip might do that for you.

Lastly, you want a manual override. That'll probably be the least complicated part. Get yourself a (on)-off-(on) toggle or rocker switch. Make one side juice the relay and the other side not.

Check this site out for all sorts of different circuits - you can probably find all of the components to put the whole thing together. http://www.discovercircuits.com/

Hope that helped some. Like I said, I'm not a EE guy (software is my trade) so let that be a disclaimer. And maybe some more knowledgable guys around here will correct/improve upon my ideas.

more mods · 09-10-2004, 04:09 AM

Quote: Originally Posted by mushin

You're either going to want a timer circuit or some shutoff switch so that the motors stop after the requisite amount of motion.

I was thinking about a micro switch that would trip at the end of the travel, but i'm not an expert on this matters either.

more mods · 09-10-2004, 07:49 AM

Now i'm really getting stoked, check out these motors.
Hey, dont forget to come back to tell me how to wire this thing!

mp3oplecarrier · 09-10-2004, 08:41 AM

I built a sliding metal cover for the ignition keyhole and radio slot on an open kit car. I used double pole relays wired to 'hold' on when tripped by a momentary pushbutton, one each for open and close, and then a microswitch at the end of each direction of travel to break the circuit... The first time I tested it the microswitch cut the power, but the inertia of the motor and all the various gears turning, meant half as pound of sheet metal mashed its way through my switches! I eventually managed to get it working with house alarm style reed switches and magnets. No pics I'm afraid, this was before the days of digital cameras!

Carter · 09-10-2004, 09:19 AM

I am also doing a reverse polarity motor idea. Mine is just to lower and raise the screen to hide and show my a/c controls. I was thinking of doing a motor with a sprog wheel and a sprog belt attached to the screen via a axle of some sort with a sprog wheel on it. This way it would pull the screen open and close it.

Microswitches would be a great help here. Anyone know where I can get some at?

more mods · 09-10-2004, 09:24 AM

Quote: Originally Posted by mp3oplecarrier

I built a sliding metal cover for the ignition keyhole and radio slot on an open kit car. I used double pole relays wired to 'hold' on when tripped by a momentary pushbutton, one each for open and close, and then a microswitch at the end of each direction of travel to break the circuit... The first time I tested it the microswitch cut the power, but the inertia of the motor and all the various gears turning, meant half as pound of sheet metal mashed its way through my switches! I eventually managed to get it working with house alarm style reed switches and magnets. No pics I'm afraid, this was before the days of digital cameras!

This is the motor I was looking at. I dont think it's strong enough to break anything and its so tiny, it should fit easily into the space I have. I just have to find a way to step 12v down to 5v for it. Any ideas on the best way to do that?

Miniature Metal Gear Motor - 62 RPM

This small 1.14" (29mm) by 0.47" (12mm) by 0.39" (10mm) motor features a high quality, all-metal 196.6:1 gear train for smooth, quiet operation and a long operating life even under harsh conditions.

The motor delivers 62 RPM with 46 in-oz torque (3300 cm-gm) while drawing an efficent 120ma at 5v DC. It weighs 0.29 oz (8.2 gram). It has a 3mm diameter "D" shaped output shaft. The shaft can be mated with most 1/8" hole output devices including 1.25" Rubber Wheels. The faceplate contains two mounting holes threaded for M1.7 machine screws such as M1.7 x 4mm Machine Screw. Mfr. # NA4S

Ninety8NeonACR · 09-10-2004, 09:32 AM

I don't know anything about how to do what you want, but the first thing that came to my mind for doing what you are trying to do would be to use a servo for a remote control car or a linear actuator.
Chris

Carter · 09-10-2004, 09:34 AM

I've looked at linear actuators before...expensive...I was going to use actuators for my project but I can't find any that are small enough to do wha t I want to do.

more mods · 09-10-2004, 09:40 AM

Quote: Originally Posted by Ninety8NeonACR

I don't know anything about how to do what you want, but the first thing that came to my mind for doing what you are trying to do would be to use a servo for a remote control car or a linear actuator.
Chris

I thought about a servo or stepper also, but then I have to have a controller, because they need PWM. I'm not sure how to set all that up, it would also add a good bit of cost to my project.

Carter · 09-10-2004, 09:44 AM

If we could find a linear actuator that was say 3 or 4 inches long. an actually moved 2 or 3 or 4 inces. It would work perfectly for both of our projects. I would need 2 though. Then you could control it through a regular dpdt relay.
The volts it ran on woulnd't really matter because you could get a zener diode to reduce the voltage.

more mods · 09-10-2004, 09:54 AM

Quote: Originally Posted by Carter

If we could find a linear actuator that was say 3 or 4 inches long. an actually moved 2 or 3 or 4 inces. It would work perfectly for both of our projects. I would need 2 though. Then you could control it through a regular dpdt relay.
The volts it ran on woulnd't really matter because you could get a zener diode to reduce the voltage.

I don't have that much space, plus I have not seen any linear actuators that small. A screw drive might do the trick if you could find one small enough. I plan to mount something like a servo horn on the motor then attach a rod to the end of it, the the other end will attach the monitor (the way the brace works on a folding table).

MikeH · 09-10-2004, 10:14 AM

More Mods,

Just for my Atlanta brother!! Here's an idea that might work. The "in" and "out" are microswitches that detect when the screen has reached it's final position and shut off the supply to the motor. The DPDT switch should have a "center off" detent so that you can stop the screen in mid position and manually jog it in or out. I used +12V in this example. I would suggest you keep looking for a +12V motor so that you won't have to find +5V some where. Although, you could get a cheapie Radio Shack adapter that puts our 4.5v or 7v...

Let me know if you have any questions!!