power door locks for my screen border

hello.  i have a 135" diagonal front projection screen i made myself and only need to finish my border to complete the project.  for my border i need the top and bottom borders to move at least 1/2" upward and back downward to compensate for different movie aspect ratios. 

i've already started my project by using magnetic cabinet door latches, the kind you'd use on your entertainment center glass doors and what not.  these sort of work, but there is lots of slop in their implimentation.  and they are manual so i have to get out of my seat and manually depress them to move them up or down.  my newest idea is to use 4 power door lock motors in the place of the magnetic latches.

so my question is, are power door lock actuators "latching" mechanisms?  for instance, my top border is 131" X 3.25" X .063" thick aluminum.  it weighs i'd guess about 6-8 lbs.  so if i used 4 door lock actuators to keep things from binding up, would gravity allow the top border to fall down in the "unlocked" positions of the 4 motors?  and does anyone know the average travel from locked to unlocked postions of most power door lock actuators?  i see many claim to have about 3/4"-7/8" travel/plunge.

also, to power this i'd need an ac to 12 volt power converter.  i don't want my house to burn down.  do you think a cheap "cigarette lighter" to in-wall ac adapter could be soldered into to power the control box of 4 motor door lock kits?  ebay has inexpensive $30 4 actuator kits complete with 2 remote/keyfobs.  this would be so friggin' sweet to sit on my lazy bottom and use the remote to move my top and bottom borders to compensate for different aspect ratio movies instead of having to get up and manually depress both top and bottom borders by hand. 

any guidance would be greatly appreciated!  this place has helped me in the past when i installed my very first alarm with no prior experience.  a 5902 into a 2001 chevy silverado.   i love this place.

Bill.

Seems like a lot of work just to move the border less then an inch. (However I do hate the black bars too myself) From how I understand door lock actuators, they "float" in a neutral position and when you apply voltage in one direction, they "pull" and when you switch polarity they "push" making the movement of the push/pull of the lock plunger. How about a linear actuator? A quick search will find some lower power short stroke ones in the $75 range. If your top molding is slotted or allows for up/down movement and doesn't weigh much this would be a more solid approach. Setup a limit switch one both ends and you can adjust your travel stops. Relay section here on the site has the wiring info to control direction. Actuator Wiring Need to implement the limit stops though. There are some affordable wireless controls out there too with small remotes to control this sort of a setup. 2ch Remote Never used these myself but some people on a different forum were using them as remote shut downs on their kids modified power wheels. Given your screen size not sure what the total distance required is for resizing the different aspect ratios however I think a "fluid movement" of your border via the linear actuator would be way cooler then the bang/bang movement using door lock actuators.

thanks for the advice.  thing is, i HAVE to use 4 or more actuators per top/bottom.  this is because the 16ga aluminum is much flimsier than i had originally planned.  i got it cut on our laser at work.  so the $75 per linear actuater would cost far too much.  i've already thrown away $37 on 8 magnetic latches, so that stings a little.  i really don't have too much money to go all out these days so i have to think cheap and inexpensive. 

but if those actuators "float", i'm not sure if they'll work for me.  not like a motor that used some sort of lockout of some type.  but being that the strips themselves weigh less than 10 lbs and those 10 lbs would be evenly distributed between the 4 actuators, they'd only need to hold up 2.5 lbs each in the up positions against gravity. 

i'm using the zoom method on the panasonic pt-ae4000u projector.  my idea works with the push/magnetic latches, but it's not as user friendly as a remote control with motors would be.  if i don't get one of the 4 latches to catch the internal stop, then i gotta find out which one and try to force that one open or closed.  the 16ga is sorta flimsy and this happens from time to time.  if it were rigid like a piece of carbon fiber, maybe.  and yes, those 1/2" slivers don't bring a smile to my face.  my projector throws good blacks for sure, but there's just enough ambient light in the room to make the slivers visible.  even after i've painted my walls black.  so the work i've already done is worth it and i'm willing to do a little bit more to automate it. 

i should have gone the 4 door lock kit from the get-go and there are sets of 4 for only $30 shipped.  though you do get what you pay for and i have no idea how much travel they have.  if it's more than 1/2" i can make stops for them.  but if they "float" as you say, even with only 2.5 lbs needing to be held by each actuator....the SVS subwoofer may shake these enough to allow gravity to foil my plan.

I would think the actuators are nothing more then a cylinder inside a coil. So when you energize one direction it pushes, and reverse it pulls. I don't have any experience with them myself, I'm sure somebody else can confirm/deny my thoughts. If you are stuck with using or attempting to use the door actuators, then another option is a latch/magnet at both positions so you can push it one direction and latch it, then pull it the other direction and latch it... Eliminate the whole floating aspect, however I don't imagine they would have enough travel for you... If it has +/- 0.5" travel and you latch it at one extension, in theory you would have 1" travel but I don't know how it would react to energizing it while its not "floating".

that's just it. guess i won't truely know unless i try. either it'll kick ass or it'll be a waste of $30. what to do...what to do....

I'm sitting with an actuator in front of me and measuring the plunge i'm gettin around 2cm push or pull, would this suffice?  An actuator would remain in the position it last shifted to once it's attached to something fairly rigid, however with this setup you will onle be able to move it a to a certain distance i any direction namely 2cm, since actuators as mentioned before move bang in either direction there's no smooth flow that allows you to stop movement at a desired point.

The lock actuator will not be accurate like you think. It will extend out but not stay in place afterwards like a linear actuator(which is very accurate). Can't you renforce the aluminum to accept a single acuator?

A thought, leave the magnets in place to hold the screen where you want. The lock actuaors should break it free from the magnets...

Mike M2

Tech Manager

CS Dealer Services