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Topic # 201621 26-Aug-2016 22:41
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I guess this could go here or in the workshop space, but... I'm building a DIY super accurate projector lift to stealth my HT projector... I'm modelling it on this...

 

 

 

 

So far I have ordered the linear actuator, 12v relay to emulate a DPDT switch based on 0 or +12v (which will come from projector), pillow bearings, shaft and shaft mounts.

 

I have to decide if I will draw up the metal frame and get it lasercut, or just make it out of right angle and flat aluminium. Shouldn't be too hard either way.

 

I've never been confident in the repeatability of drops with any of the ones that come down on a scissor drop but this one could be super accurate. I will have self locating spike and receptacle stops at the bottom of travel so it's effectively hard mounted every time it drops.

 

Now just have to hurry up and wait for Aliexpress vendors to send me all the bits.

 

 

 

Cheers - N

 

 


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  Reply # 1618156 27-Aug-2016 00:53
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Just make sure you don't accidentally retract it whilst the bulb is still warm.

 

 




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  Reply # 1618357 27-Aug-2016 16:15
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I thought about this myself but for a few reasons I am going to go ahead and basically ignore the issue...

 

- Several professionals at high end shops said not to worry, both to the explicit question, and also to a question about whether the lifts they had supported a delay.

 

- The practicalities of adding a delay circuit, while I am sure are simple, and could possibly be solved by a $5 part from Aliexpress, are something I don't care to worry about.

 

- I am building in a soft start and soft finish to the up/down. (Down has springs to compress on the locating pins for when it rests into position and the actuator won't be hard mounted - it will have an elastic component)

 

- I'll have a counterweight to reduce the stress on the actuator and make a much smoother movement

 

- I have a spare BNIB bulb on a shelf :-)

 

 

 

All that said, I have seen simple delay circuits that I might look into. If someone had an example of an Aliexpress sourced way to do a latching configurable delay of the 12v signal to keep it high for a set time after the projector goes off, I'd probably consider it :-)

 

Using the 12v trigger from the projector to switch the lift means I can't build a delay into the startup so I an relying on building a super smooth lift for that part of it.

 

 

 

Cheers - N


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  Reply # 1618454 27-Aug-2016 20:18
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Check the manual of your projector for the trigger options. Some not only allow for on or off but also delayed operation. However check for limitations of only on switching or off switching.

If you haven't used relay servo controls before, it would be wise to plan out a logic flow path(diagram). Sometimes these things can seem simple as a switch on/off but often you really need a logic controller activating the relay(s).

I'd note you will need power for the projector up there and probably a 12v PSU to drive the motor, so you can take advantage of the PSU to drive logic, relays, wireless.

One of the concerns about the lamp cool down is actually because you need to create an enclosure for the unit to reside in, so you don't want to try and cool projector in an enclosed space.




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  Reply # 1618480 27-Aug-2016 20:39
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All good thoughts but I checked (and tested) and my projector can only delay the 12v turn-on (2 - 30 seconds), not the turn off. It explicitly states "12 V cannot be output from the trigger terminal when the projector is in standby mode" so that won't work.

 

The projector is a Panasonic AE7000, and has 2 trigger outs which is nice (one for screen and one for lift) so I don't have to split the signal.

 

The particular relay I have ordered is, it seems perfect for the job, it operates as a DPDT switch based on 0 or 12V so when the projector is off it will be supplying power to the linear actuator but the actuator has it's own limit switch so no issue there. Ditto for the down direction - when it's getting +12 it will always be pushing the down button, but again a limit switch will sort that out.

 

Power is being handled properly - the projector location will need power for the projector, for the actuator, and USB power for an IR repeater, and perhaps for a wireless relay as well. This is for a new build so having power wired into the ceiling space there.

 

I'm not concerned about heat buildup in the enclosure there - worst case scenario the projector cools down slower than it would in free air... With the lift being driven by the 12v trigger it won't be able to be stuck on up there while fully powered on. (It might spend more time in cooldown mode with the fan on after poweroff)

 

 

 

I was going to replicate my DIY for the screen as well but I have decided to treat myself and get a proper ceiling concealed dropdown screen with all the nice fascia etc.

 

 

 

I may look for a circuit to hold the 12v trigger up for a few minutes - I am sure there's a $5 part available to do that easily - it's just reverse engineering the terrible descriptions on Aliexpress that is taking the time.

 

 

 

Cheers - N

 

 


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  Reply # 1619341 29-Aug-2016 21:20
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I advise you look at a simple logic controller, 2~4 inputs similar outputs.

A logic controller is a relay bank that you can program. Remember relays are more or less dumb, add some logic and you can make decisions about time, even trigger your screen.

I purchased spare remotes for my screen and roller blinds so as to hot wire the buttons with relays triggered off the projector for a start. I'm eventually going to use a logic controller.




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  Reply # 1619343 29-Aug-2016 21:27
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Or just add a cheap low speed 12v PC fan as an 'extractor' for the enclosure. At a measly 0.3A/12V it's about 3w of power and could easily be left on continuously, or wired with a short timer, and wouldlikely suck cool air through the sides of the drop down platform to happpily cool the projector and provide a good source of fresh (low dust) air there too.



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  Reply # 1619917 30-Aug-2016 21:06
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Situation... I am confident that this device:

 

 

 

 

Will drive a linear actuator from the 12v trigger on the projector... BUT I'd also like a remote switch, and whatever way I do it in my mind, I am going to have effectively 2 DPDT switches connected to the actuator simultaneously.

 

 

 

I was thinking this for a remote controlled relay for it. (220VAC, 10A, configurable momentary or latched)

 

 

 

 

But this leaves me with the possibility that the projector and the remote could be actuated at the same time, either in concert or against each other. I haven't sat down to draw it all out yet, but is this likely to burn my house down or just cancel each other out at worst?

 

I guess the more general question is, how do I have automatic triggered operation from the 12V trigger and a manual switch? (I don't want to learn/use an arduino or something stupidly overkill in there)

 

Cheers - N

 

 

 

 

 

 

 

 




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  Reply # 1619931 30-Aug-2016 21:29
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Bah - I'm an idiot... Combine on the input side...

 

use the 12v trigger DPDT relay just as a switch to drive this..

 

 

 

 

 

 

replace the up and down switch on the fixed unit with wires to the 12v trigger relay outputs and use the remote as my manual switch.

 

Nothing to see here, just needed to write stuff down to see my original plan was idiotic.

 

Cheers - N

 

 




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  Reply # 1621713 2-Sep-2016 23:09
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So a few minutes with some 50% mockups is a LOT easier than trying to draw it. All parts on the way... Just have to get some aluminium RHS and MDF to make the mounting frame and articulated section. The sides (in white) will probably just be flat ally bolted together to start with and upgrade to ornate lasercut panels when it's ready to go in the ceiling. Not shown here is an adjustable panel on the bottom to cover the hatch when closed.

 


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