Ability to drive multiple IR transmitters independantly from PC

I'd have to guess that Xantech has something that could be put together to setup the necessary zones. Likewise also arrange a PC interface.

Hi,

If I understand the above, you just want to swicth the displays on and off; not control any other parameter. In which case, why not just switch the power?

This would be fairly trivial upto 8 channels by simply using the PC's parallel ports to drive a couple of relays; there are a few utilities that let you do exactly that; control each bit on the port. Beyond that, you could use a PIC with lots of outputs, and connect it to the PC over the serial port. The PC indicates to the PI(C what to do with each i/o bit.

Regards,

Anand

Sorry, intended to include this link the last post:

Regards,

Anand Dhuru

ved snipped-for-privacy@hotmail.com wrote:

What's the distance from PC to displays?

USB has limited distance on the USB cable length. However, you could use an external IR emitter with a long lead. This may require disabling the internal emitter to prevent it from affecting multiple receivers.

The question is whether the PC can distinguish between multiple USB IR modules.

I would ask the designer of USB-UIRT if you can use multiples. If so there is an API for these devices and they are reasonably priced.

Ok, here's another approach; a hybrid of dave's solution and mine.

Use my solution (above) to select the channel, and the particular relay drives the USB IR's IR LED. You would then need only 1 USB IR. You would have to hack it to get to the IR LED output.

On the PC, you'd need two commnads to be sent; channel select and on/off.

Also, you would have 1 transmitter per display, so the concerns that Dave mentioned would come into play unless you shield each LED and leave a very narrow aperture, and then place it in close proximity of the individual displays. I have had excellent results using black heat-shrnkable tubing to achieve this.

Regards,

Anand

Dave Houst>

Hi Alexis

Just a pity it wasnt multiples of 8 devices......

If so you could use my FirM hardware (which was initiailly designed for Homevision HA Controller ,BUT would require a homebrew serial interface) ..You would also require a USBUIRT to learn and generate the ir signal...

You could still use the USBUIRT and Make up a Homebrew serial interface which the computer sends commands to it to tell it which zone the ir signal is going to then send via the USBUIRT.....

Hi Anand,

That's a very good question, and one I should have clarified in the original post - the displays in question are projectors, and as such, cutting the power to them without allowing them to shut down correctly drastically reduces the lifetime of the bulb. When they receive the 'off' IR signal, they enter a rapid cool-down mode lasting about 2 minutes, where the cooling fan runs constantly.

In addition, I believe that they do not default to the 'on' state when power is initially applied.

Thanks,

Alexis.

Ranging from about 5 metres to about 20 metres - I had planned to either use USB repeaters or IR LEDs on a long bit of wire, either of which should be adequate workarounds for the distance, I hope.

My concern with this solution is that it will probably work for a small number of devices, but I have concerns as to whether it will work with the full complement of 20 devices. I am unsure as to how the USB UIRT device interfaces with the PC. If it acts as a virtual serial port, I suspect this may be an issue, as Windows will, as far as I know, only support a maximum of 16 COM ports active at any time. (For the record, using Linux is sadly not an option in this case).

If anyone can clarify whether this would or would not be a problem, I would be interested - at the moment this is only my guesswork, but it's an expensive experiment to find out if I'm right!

Sadly not - they are identical and there is no support for coding of the IR transmitters and receivers.

Thanks!

Alexis.

Thanks Bill - their IR Router seems to do the majority of what I need, although by the look of it I'd need to send it IR commands to switch between channels - but this wouldn't be out of the question.

It is quite an expensive solution though, especially as a single 8 port device wouldn't quite cope with the 10 existing displays, necessitating two. I also need to read up more on how to control two routers independantly. But it's a promising possibility!

Thanks again!

Alexis.

Hi again Anand,

Now that is a very interesting solution, that I hadn't considered at all. It has the slight downside that global device control (i.e. switching on or off multiple devices simultaneously) takes a little longer, but the time taken should be acceptable.

I especially like that it is effectively infinitely expandable, as you would just need additional switching relays. Do you happen to know if there are any schematics detailing how such a switching system might be implemented online? I will have a look myself later tonight.

This isn't too much of a concern due to them being projectors - they have two IR reciever windows to allow them to be controlled from multiple angles, so it's no issue to tape the IR transmitting LED to be in direct contact with the IR receiving window, and block it out from transmitting elsewhere.

Thanks again!

Alexis.

Hi Frank,

I actually came across your system last night after posting, and it did seem to have a number of characteristics that would make it very suitable for this application. Unfortunately, the cost is the main prohibiter - am I correct in estimating the cost of controlling 10 devices as being:

Total cost $1150.00

Unfortunately that's a little more than I'd ideally like to spend, although I appreciate that it's worth the price for the flexibility, and I love the ability to hook up receivers using simple CAT5 cabling. I also appreciate the cost would have been significantly less if there were only 8 devices to control!

Many thanks,

Alexis.

USB repeaters are costly compared to long IRED leads.

Windows supports 256 COM ports so this should not be a problem. However, although they use FTDI USB-serial chips, I don't think USB-UIRT uses virtual serial ports. That's why I suggested you contact them to be sure they can distinguish between 20 devices. I believe FTDI provides for this by giving you a way to assign an ID to each device but its been too long since I looked at the details. (These days, a few hours is too long.:()

Since you were talking about USB repeaters I assumed cost was not a factor.

What are the details on the codes you need to send? Carrier frequency, code? It may be possible to design something quite cheap to accomplish this. Can you program in Basic?

Hi Dave,

That's interesting, thanks. I shall definitely get in touch with them and see if they can clarify the maximum number of devices a single PC can realistically support.

Cheers,

Alexis.

Cost is always a factor! ;)

To be honest, I hadn't really considered the cost of USB repeaters as extending the IR LED wiring was always my first plan - my soldering skills, while not fantastic, are more than up to the challenge of that. Anything involving breadboard and through-hole components I can usually manage, as an indication of my capabilities - but I don't have the kit to do surface-mount soldering.

For the record, I'm not at all adverse to paying for a commercial solution, but it needs to not be *too* expensive. Say a maximum cost in the region of $500-$750 for 10 displays - ideally less, of course!

I have to admit to my ignorance on this unfortunately. The projectors are NEC VT650 models, but unfortunately I'm unable to find any details of the IR specifications on the 'net. Is there anything you can suggest without knowing this information?

Java is my programming language of choice - I've done projects that interface with parallel and serial ports from within Java, so if you have something like that in mind, I should be able to build the code to drive it without too much difficulty. I also have plenty of friends who can code in C/C++, and I'm sure some of them will have Basic skills, so I'll figure something out on the software side if you can give me some hints on the hardware side!

Thanks again,

Alexis.

This woould be fairly simple to do in ZBasic (free) running on a ZX-40 (30 pins could be used to control 30 projectors) which costs $30. You need a transistor and a few resistors in each circuit. You can buy surplus emitters with long cords and wire as needed to extend them. Total is probably under $100 built on vector board.

If you cannot find the codes on RemoteCentral it's a simple matter to capture them with a sound card. See...

Anand can point you to another site that has an alternate method of capturing the codes.

If all else fails, buy one USB-UIRT to capture the codes and carrier frequency.

Since you used meters when referring to the cable length I guess you're not in the USA. You can probably find similar emitters elsewhere.

If I had $70000 worth of projectors I'd probably feel I had enough clout with whatever dealer sold them to get the IR codes. ;-)

I did a little research and here's what I found out so far.

PC serial codes:

POWER ON 02H 00H 00H 00H 00H 02H POWER OFF 02H 01H 00H 00H 00H 03H INPUT SELECT COMPUTER 02H 03H 00H 00H 02H 01H 01H 09H INPUT SELECT VIDEO 02H 03H 00H 00H 02H 01H 06H 0EH INPUT SELECT S-VIDEO 02H 03H 00H 00H 02H 01H 0BH 13H INPUT SELECT DVI (DIGITAL) 02H 03H 00H 00H 02H 01H 1AH 22H PICTURE MUTE ON 02H 10H 00H 00H 00H 12H PICTURE MUTE OFF 02H 11H 00H 00H 00H 13H SOUND MUTE ON 02H 12H 00H 00H 00H 14H SOUND MUTE OFF 02H 13H 00H 00H 00H 15H PROJECTOR INFORMATION REQUEST 00H BFH 00H 00H 01H 02H C2H ERROR STATUS REQUEST 00H 88H 00H 00H 00H 88H INFORMATION REQUEST 03H 8AH 00H 00H 00H 8DH

IR Codes: Power On: F7 Power Off: EB Enter: E8 Cancel: DA Menu: B9 Help: B1

There are more. If you need them, let me know.

Hope that helps.

What program in the computer will do the control? Is the computer deciding when each projector gets tuned on/off? If not, have you considered a box with 20 buttons, one for each projector?

Since you don't need "any and all" commands to be sent to the projectors, you could use a remote (or something that can learn the IR pattern) with a long wire between the LED and the remote, then a signal from whatever the triggers the remote.

If all the projectors respond to the same signal, one remote could be wired to all the LEDs (with appropriate buffering) via a control matrix that would connect the remote to the correct LED(s) and triggers the remote. That could be done without a computer (a small amount of logic and some transistors) or could be done with a simple digital output card.