ILDA Signal Current Requirements

[cfavreau]

Does anyone know or know where to find the maximum current draw for the signals on the ILDA connector? Such as X,Y,I,R,G,B ?

Thanks!

[DZ]

This is straight from the Pangolin Projector Connections article:

The ISP specification allows for voltages up to 25 volts, and currents up to around 160 milliamps to exist on the DB-25 pins. Thus, the projector interlock must be facilitated in such a way that these values are not exceeded. However, I recommend that you try to implement an interlock that uses far less voltage and current – for example 5 volts and 5 milliamps. This could be done using an electronic relay instead of an electro-mechanical relay. The interlock signals may also be implemented using other methods that might provide an increased level of safety – for example, by outputting a small sine-wave signal on pin 4, and comparing it to the voltage received on pin 17.

I don't see anything specified in the ISP document. I would hope most devices out there have around a 10K input impedence, which would put the current per pin at less than 1mA.

[mixedgas]

I have THE ORIGIONAL standard. You need to support a 600 ohm impedance, which is a bit different then a pure 600 ohm load.

I have posted the ILDA specified driver and receiver here many times. I'll see if I can find the PDF and get you a link. Even the cable type and impedance is specified in the thick three binder. I've always wanted to scan the whole thing in, but I fear ILDA enforcing its copyright.

DZ, its not in the ISP standard, its in the three ring binder ILDA handed out for the first five or so years of its existence.

Steve

[mixedgas]

See attached, the smileys let me access my old attachments, its a quirk in the forum software, attach a new file and then and only then can you get at the old attachment. Saved me a horrendous search time. PS, the first specified connector for the ISP was a 36 pin CPC, allowing two independent projectors on one cable. The sudden availability of 24 pin printer switchboxes caused the shift to the Dsub.

I'm on the road, it will be two days before I can post the standard digital line driver schematics and specs. They DO exist.


The 150 Ohm resistors in the output lines exist for a reason, and the TL08x is internally limited to about 20 mA.

Steve

[mixedgas]

DZ's description covers the interlock loop, which was designed to have enough current flowing through it to ensure a working interlock across dirty connections.
Ie "sealing current" as the phone company calls it. The rest of the digital signals are far different.


Steve

[mixedgas]

I have THE ORIGIONAL standard. You need to support a 600 ohm impedance, which is a bit different then a pure 600 ohm load.

I have posted the ILDA specified driver and receiver here many times. I'll see if I can find the PDF and get you a link. Even the cable type and impedance is specified in the thick three ring binder. I've always wanted to scan the whole thing in, but I fear ILDA enforcing its copyright.

DZ, its not in the ISP standard, its in the three ring binder ILDA handed out for the first five or so years of its existence.

I'll post more when I get home in two days, there is a defined current limit.

Steve

[cfavreau]

Thanks for the information so far.

Ok... so I am not really concerned with the interlock....

I found the projector standard fromhttp://www.laserist.org/StandardsDoc...finaldraft.pdf

So what exactly does 600 Ohms impedance mean for a circuit trying to drive that load? Is that 16 mA at 10Vpp?

I am trying to design a dual rail power supply to feed some opamps and need to know how much current to expect when trying to drive a projector.

Thanks very much for the replies. I really appreciate it.

[DZ]

The rest of the digital signals are far different.

Digital?

I have THE ORIGIONAL standard. You need to support a 600 ohm impedance, which is a bit different then a pure 600 ohm load.

I would seriously hope that none of my projectors have an input impedence of 600 ohms. The standard calls for 100 to 150 ohm resistors on the output of each signal. You input impedence needs to be closer to 10K.

So what exactly does 600 Ohms impedance mean for a circuit trying to drive that load? Is that 16 mA at 10Vpp?

If your DAC has 150 ohm output resistors then you will lose 25% of your signal before it gets to the projector.

[mixedgas]

Less then 24 hours to posting the data, all of it. I'm in Ann Arbor, it is a 8 hour day at the clients and a three hour drive home in the morning. At that point in time one Mahoosive PDF is going to be created.

You need the 150 to drive a potential shorted line while protecting the Op-amp. However with care and some testing the feedback can be moved to the other side of the limiting resistor, ensuring full drive into a normal load.

150 into a 1 to 10K image size potentiometer is not going to cost you much signal.

There is/was a optional digital signal section of the ILDA protocol, including high speed serial to the projector.

The standard, as designed, was far more capable then what was implemented when dropping pins to go down to the 25 pin connector. It also used a cabling scheme that would have held up better at Gigs. However everybody wanted to go to a lower cost cable. I have read about countless people who have had trouble because of this drive to cheapness.

Steve


Steve

[cfavreau]

I am just interested in the analog signals..... you know the ones typically hooked up to a DAC or other variable voltage source. I.E. XYRGBI etc.

Digital?



I would seriously hope that none of my projectors have an input impedence of 600 ohms. The standard calls for 100 to 150 ohm resistors on the output of each signal. You input impedence needs to be closer to 10K.



If your DAC has 150 ohm output resistors then you will lose 25% of your signal before it gets to the projector.

Pardon my lack of knowledge... how do you calculate your signal loss?