DC motor and relay question...need help please

Hey everyone,

Thank you for taking a look at this and helping me out. I need advice on what types of motors I should use for this application. I have put the key items in bold so you can skim through this without having to reading everything.

I am creating a flip-out screen for my car GPS (I am tired of my windshield mount GPS being stolen). It will be hidden in my dash when the car is turned off, when the car is turned on it will flip up and when turned off it will return to a hidden position.

So,

1) 12V DC Current, both need to activate in one direction when the car is turned on and return the other direction when the car is turned off. To do this on a DC motor it would just reverse the current. What kind of switch would this be?

2) I need the one motor to travel 90 degrees in a few seconds (two or three seconds). This will make the screen go from parallel with the ground to a viewing angle.

3) The second motor needs is to travel a few inches in roughly the same amount of time, doesn't have to be exact. Same situation with the car power on and off, but the problem I'm running into is how to set the limits of travel. A friend suggested an infra-red beam that is broken etc. Also, what RPM is suggested for the motor? I was planning on using a belt to move the bottom of the screen from the back of the housing to the front.

4) Some sort of electrical delay. So if I put the ignition in the on (without engine started) and then start the engine a few seconds later, the unit will not flip up, then down suddenly, then up immediately. This is not the biggest issue, but would be nice.

I need help with what kind of motors to use (Step Motors, Brushed vs Brushless Motors, Limited Angle Torque Motor, etc), do I need an encoder, what kind of switch is needed. It will not be moving a lot of weight...two or three pounds max.

I have a few sites that I have been researching below. Thank you for your help!

- Alex

Site 1) [www.firgelliauto.com]
Site 2) [www.firgelliauto.com]
Site 3) [www.h2wtech.com]

You really only need one motor, probably a linear actuator.

By far the easiest would just have the screen on a pivot that turns as the screen comes out of a drawer, or goes back into its drawer.

As for sensing when it has got to the point you want, surely you could just get away with simply micro switches.

A relay in your car that turns on the motor till the actuator hits a switch, folded out and viewable. when the ignition is off, the relay is off, causing current to flow in the other direction in the motor, till it hits another switch.

why are you asking here? this forum is for reprap-related stuff, not miscellaneous robotics design. you'd get a far warmer reception on pololu or similar forums

Grogyan- Thank you for the suggestion, I will research Linear Actuators. As for the drawer, this will be sitting on top of my dash which is almost parallel with the ground. I don't know if that will work out for me in this situation, thank you though for the suggestion.

Triffid_Hunter- I have been researching stuff like this on many sites and saw some DC gear related posts on this site, I though that I could get some suggestions from here. I am about to visit pololu right now, thank you for the suggestion!

If anyone has any suggestion please post! Thank you all!

You might look at damper motors. These are used to actuate smoke dampers in the ventilation systems of large buildings. The ones I've seen are 120 volt, and much to big, but have spring-loaded return, rotate through 90 degrees when power is applied, and use 1/2 the current when "holding" open.

So if you could find a small 12-volt one it would be ideal for your application.

I have no idea if such a beastie exists though.

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I'm building it with Baling Wire