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I'd like to install a JVC DLA-HD100 projector but I need it to control the drop down screen on turn-on. Most projectors have a 12v trigger output, but as you mentioned in the What Hi-Fi review of the JVC, it doesn't. It only has RS232. So how do I convert the RS232 signal into a 12v trigger signal? What device can I buy to do this?

Wow, a whole bunch of you have read this and not one single piece of advice. Don't any of you at What Hi-Fi ever do installs with this kit and have to tackle problems like this? Please guys, any help at all, much appreciated.

We don't actually do installs, but I can't think of a way of doing this.

Hi Will,

Do you have any info on what the RS232 output does? Presumably, it is intended to communcate with a particular bit of kit? I know nothing about projectors - is there a menu option to tell it to drop the screen when turned on then?

As RS232 is a serial interface, we'd need to know how it talks to other stuff. We could level shift the RS232 to 12V, but what would your screen think to a whole stream of on's and off's? It might go a bit crazy.

Maybe level shift the RS232 data to TTL, shift it into a register and compare it with the drop screen command and if it matches, output a 12v pulse?

Would you also need a command to retract the screen too? Or is the input a toggle?

I might be barking up the wrong tree though and missing the point..

The 12v signal is a really simple deal, it's either on. Or it's off. When it's on, the items programmed to switch on in the presence of a 12v source come on and stay on until the signal switches off. It's that simple.

My electric projector screen can therefore be set to come down on the presence of a 12v trigger signal and when the signal switches off it'll know to retract.

The JVC doesn't output a 12v signal. It only has an RS232 port. So what are my options? Please, someone who actually knows the answer reply.

Most grateful!

And thanks Andrew. I know you guys aren't install experts, it's just that's it's such a big part of making a system work these days, that I was hoping some expertise might reside in WHFSV Towers ;-)

I'm not an expert in this field but after a very quick look at the manual on line, it looks like there are only 3 pins connected on the RS232 port of the JVC;  One to receive data, one to transmit data and signal ground.  I would hazard a guess that this means you can't do what you want to do using the RS232 port.  You might be better off looking at some solution which uses a relay to simultaneously switch on the projector and drop the screen but again, I'm not in my area exactly here so take my thoughts with a pinch of salt.

Mate I'll look into it. I was hoping someone might tell me of the existance of a little box, into which you plug the RS232 lead and power, and out of the other end a 12v signal can be connected. That's what I'm hoping for!

There is a little box for any projector without a 12v output. But it connects in line to the power not to RS232. When the projector is on, the power is sensed by the box, the box outputs 12v from it's own trigger output. Projector off and the box shuts the 12v back down again. Easy when you know how ;)

Will Harris:

Please, someone who actually knows the answer reply.

Erm, OK - first of all you moan that no-one has replied. I then try and help by finding out some info from you - then I could have knocked something up. Then your quote above.

Some people, eh?!

Actually, Liam has experience of doing this kind of install with JVC products and suggested a real solution.

I am not going to respond to you, Bloney, because basically you're a nice bloke trying to be helpful, but really you took my comment and saw the worst in it. It wasn't meant as a criticism of you, more a sort of hold your hand to the sky and beg the heavens for someone really knowledgeable to step forwards, which they did.

So please don't get so upset.

And thank you to Liam. That was just the solution I needed. I'll give you a call and maybe I can design a system with a few components bought from you that will do the job, marvellously. Now THAT is what forums are for.

Will Harris:

I am not going to respond to you, Bloney, because basically you're a nice bloke trying to be helpful, but really you took my comment and saw the worst in it. It wasn't meant as a criticism of you, more a sort of hold your hand to the sky and beg the heavens for someone really knowledgeable to step forwards, which they did.

So please don't get so upset.

Hey Will, don't worry yourself, I'm not upset. I'll be ok, no need to worry.

I just read your comment:

"Wow, a whole bunch of you have read this and not one single piece of advice. "

and thought I'd take the time to try and help. I'll be the first to admit I'm not the best to help, but thought I'd make the effort to try. Then we get:

"Please, someone who actually knows the answer reply."

and thought that was a bit rude. Probably not the sort of thing you would normally say to someone without getting some grief!

Now - forums for me are about like minded people TRYING to help out. That, for me, is what forums are all about.

And wipe that smirk off your face :)