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Thread: DIY motorized lcd/pda = 1 actuator + 1 wire + 1 spring?

  1. #1
    Constant Bitrate CA 3000GT's Avatar
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    DIY motorized lcd/pda = 1 actuator + 1 wire + 1 spring?

    Been trying to think up a fairly simple, fairly easy to make, design for motorizing a lcd or pda. (having it motorize out of the dash, *and* fold up)
    Dont know if I'll get to actually making this sucker, but figured I would post the plans I have thus far.

    [key:
    1) The case is not drawn, but assumes the case is a standard head unit case, with a door in front for the LCD/pda to enter/exit.
    2) The spring is in green, the wire is in red.


    The first picture is of the mechanism "at rest" the lcd/pda is retracted.

    In the second picture, the actuator has started to push the pda forward, and the restraining cable has become taught. Since this cable cannot be stretched, and the actuator will continue to push forward.... further stretching the spring... and pushing the pda mount up (3'rd picture)

    Finally, the actuator has pushed as far as its going to go, and the pda is in a vertical position.... it's been pushed out, and pushed up!

    Now for the retraction, in many ways the most difficult part.

    The actuator starts to pull backwards, the spring, fully strained, pulls the top of the pda mount downwards (back to pic 3) and as the actuator further retracts, back to stage 2. eventually brings it completely horizontal again, and ready to be pulled in to the case.

    My actuator should arrive on Monday... but... don't know if I'll actually implement it.... thought it was an interesting design though... Might be useful to someone.
    The actuator will cost ~$100, other misc parts will cost $10-20.. If your just pushing a LCD.. Digitalww's motorized lcds are prolly the best bet. However, if you have a pda for which there are no motorized mounts, or you have an lcd that wont work in the digitalww mount, this may be an alternative worth looking into.

    In practice
    1) one would want to run a wire through the spring so if it snapped, it wouldn't whip around
    2) its necessary to have a spring with sufficient "springiness" you want enough tension bring the lcd into position, but don't want to stress the springs, or the rest of the assembly beyond what is necessary.
    3) make sure to anchor and angle the actuator exactly. I recommend using a machined mount bolted onto the car frame, or metal attached to the frame. A misaligned actuator could punch through your dash.
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    1995 SL stock
    Working On: GMAT
    Given Up On: Custom motorized lcd

  2. #2
    MySQL Error Scouse Monkey's Avatar
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    as you have already seen, actuators are expensive.

    Have you considered using an old CD rom drive mechanism? For somethign the size of a PDA they could be fine (travel is an issue for a 7" screen) and you can strengthen the mechanism and add some guides to stop it wobbling.

  3. #3
    Constant Bitrate CA 3000GT's Avatar
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    CDrom doesnt quiiite extend far enough, and wont provide the force to extend the spring.. However if yer motivated and good with a soldering iron, theres no reason why a person couldnt use a modified cdrom or a "aftermarket power window slider" (pic included)... or maybe 2 power antennas... or build their own. I am quite suprised no one sells actuator kits...

    Sure, a very motivated someone could make this for $10. However, while conceptually simple, the actual fabrication of an actuator is quite painstaking. all the gears and such have to mesh, move without play, bold&clevis must rotate w/o friction, limiters have to be soldered up, the piston part must be guided.. etc. etc. etc.. Torque has to be sufficient, and the actuator assembly has to stand up to that torque.. and a good assembly has to be able to repeat its task hundreds of times w/o maintainance.

    ShotguneFx done this this, pretty damn cool.

    In my opinion, a $100 actuator is not bad at all considering the pricing of alternitves(for lcd from digialww nearly $200, and for pda.. well... there are no alternitves) , and the significant effort involved w/ DIY actuators.. so, it was worth it for me.

    So... Ive kinda left out actuator alternitives in this design just focused just on the "out, up, down & retract" assembly.

    I mean, I havent seen any plans for an affordable, easy to implement DIY motorization, so... figured I would take a shot at it.
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    1995 SL stock
    Working On: GMAT
    Given Up On: Custom motorized lcd

  4. #4
    Constant Bitrate
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    add the dash face to the diagrams - I suspect you have interference.
    pivoting this way means it has to stick way out to clear?
    D

  5. #5
    Constant Bitrate CA 3000GT's Avatar
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    It should clear the dash face just fine if the actuator is of sufficient length.
    Im thinking 1" longer then the item your moving. So, if the pda is 5" high, a 6" actuator. How far the piston extends before hitting the limiter should be entirely a function of the length of your actuator and how the mount is configured...
    1995 SL stock
    Working On: GMAT
    Given Up On: Custom motorized lcd

  6. #6
    Newbie
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    Why dont you just use a usb controlled servo to move the screen.
    Place the servo on the back of the screen and control it with a usb device

    easy and inexpensive

  7. #7
    Constant Bitrate CA 3000GT's Avatar
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    Hmmm.. usb servos... might be good if I was designing an actuator... but... I think that would only complicate things here...
    A servo to angle on the screen would
    1. Add a 2'nd motor (in addition to the actuator to push the screen out)... If there is a design that works with 1 motor vs. 2... the simpler 1 motor approach has got to be my first bet
    2. require either mounting the servo on the screen.. where.. it would be very hard to fit it.... or.. require it to be mounted in back, in which case some cable assembly would be required...
    3. if it is a usb servo, though usb servos are cool, it would require the pda/computer to be on and booted up before I could deploy/angle the device... I suppose I could have a button for the actuator, and have the pda/computer automatically run the servo program whenever it boots... but say I have to reboot?... I would have to close & open the screen or the thing would angle twice.... or have sensors that signal the servo program as to whether the device is deployed.... seems somewhat complicated....

    In the end.. unless there is a deal breaker on the cable assembly, I think it's the simplest approach, and thus the route that in the end has the best chance of being fabricated successfully...
    I donno about you guys, but I have found the fabrication of anything with moving parts to be 10x times harder then I expected.. and things with motorized parts.. 10x harder then that... so, anyhow... the actuator was delayed.. should get it on Friday.. and soon after.. we will know if this sucker will work!!
    1995 SL stock
    Working On: GMAT
    Given Up On: Custom motorized lcd

  8. #8
    Raw Wave shotgunefx's Avatar
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    I would think you would run into problems with the limiting wire getting tangled up. If it's for a pda, maybe you could make it so the pda "wants" to be up. Meaning, have the pda on mount that allows it to swivel. With a spring going from the back of the pda to the rear of the mount tray. (You'd need bumpstops to make it stop too).

    That way, when the actuator opens, it will popup. When it retracts, the pda will be pushed forward and down.

    Something like the crude diagram attached.
    Attached Images Attached Images  

  9. #9
    MySQL Error Scouse Monkey's Avatar
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    You can use 555 circuits to set servo positions using pots. If you make a netwrok of pots that are activated by limit switches then you can control the in and out procedure and also have a small dial to adjust the tilt setting which the PDA will be set to every time it opens. The servo will also be self correcting and will not allow the PDA to move from the desired tilt angle when you press it. The onyl way to tilt it will be via the control pot.

  10. #10
    Constant Bitrate CA 3000GT's Avatar
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    Update: well, it totally works...heck, worked on the first try believe it or not... but its totally too wide to fit in a din.... and if I put the actuator behind the pda (vs underneath it) the assembly is too long... so... Im gonna take another shot at having the pda above the actuator... and then take a run at putting it next to the actuator piston.

    Thanks folks, for having a look & the suggestions.

    Scouse Monkey: that sounds awesome... but... right now my biggest concern is fitting everything... someplace in the dash... Im gonna have to wait a little before I can work on the angle... Im not sure where there would be space for the servo.. heck.. Im not sure where there is going to be space for the actuator

    shotgunefx: its a great suggestion, but in order to do that, I think I would have to put the actuator behind the PDA... and the kicker here is... the assembly ends up being like (10.4" actuator + 5.1" pda) about 16.4" which I cant quiiite find space for... I have about a foot of space.. maybe 14"...
    1995 SL stock
    Working On: GMAT
    Given Up On: Custom motorized lcd

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