DMX Testers

[Brian]

Orange (colour flicker) : All Ok (You should still get the red / green colour bias for all up / all down)

Solid Red : Pin 2 disconnected

Solid Green : Pin 3 disconnected

Off : Pin 0 disconnected

Maybe I'm missing something but if a pin is disconnected then how would you get a solid LED indication? I think you mean that you'd get a red or green flicker instead of an amber one.

[ben.suffolk]

Maybe I'm missing something but if a pin is disconnected then how would you get a solid LED indication? I think you mean that you'd get a red or green flicker instead of an amber one.

<{POST_SNAPBACK}>

 

Ok, what I meant was the colour would be pure Red, or pure Green, and not a colour mix (i.e. Orange / Amber as you said). However I suspect that the data rate is high enough to look like it wasn't flickering (although the brightness would depend on the channel levels).

 

Ben

[Brian]

OK, whilst waiting for UPS to deliver I've built a circuit of Ben's design.

 

http://www.aux99.co.uk/blue-room/dmx_tester.jpg

 

If pin 1 is disconnected then neither LED lights.

 

If pin 2 is disconnected then (in my case) the red led goes out and I'm left with a solid green which doesn't change much with different data values.

 

If pin 3 is disconnected then (in my case) the green led goes out and I'm left with a red which is solid when transmitting all '0' but flickers quite a lot when transmitting all 'FF'.

 

The tests above are for a full 512 channel frame but it doesn't seem to vary much with different frame sizes.

 

With all connected it works fine with low channel values but in the all 'FF' condition it's hard to decide it it's OK or if pin 2 is disconnected, with so little red being generated it's swamped by the green.

 

Also if the two DMX lines are shorted together then in my case I get a solid red

 

When it's working OK the 'amberness' of the LEDs is not very convincing - too green. By adding a series resistor in the green LED I improved things a bit.

 

It certainly works OK if the rig is 'black'.

[ben.suffolk]

That was speedy work Brian, I'm impressed:-)

With all connected it works fine with low channel values but in the all 'FF' condition it's hard to decide it it's OK or if pin 2 is disconnected, with so little red being generated it's swamped by the green.

<{POST_SNAPBACK}>

I Guess this isn't a problem, because you can toggle blackout and see the difference in colour, that way you know its not a disconnected pin, and that the channel values are being transmitted (well are having some effect on the signal at least)

[Ekij]

I don't think you want to be drawing current to the screen reference in normal operation. It may be OK for a tester but it violates the RS485 specification (could degrade signal reliability). I much prefer the LEDs between the hot pins and no screen/ground reference as per the original.

 

EDIT: Potentially coupling noise from the screen back onto the signal wires.

[TomLyall]

Brian, could the problems of differentiating between the colours of the LED be solved by using two separate LEDs. Then would you not be able to see fairly well?

[Brian]

Brian, could the problems of differentiating between the colours of the LED be solved by using two separate LEDs. Then would you not be able to see fairly well?

<{POST_SNAPBACK}>

It would be much clearer. The general idea with using one LED is that it'll fit into the cable gland of an XLR.

[Lamplighter]

Brian, could the problems of differentiating between the colours of the LED be solved by using two separate LEDs. Then would you not be able to see fairly well?

<{POST_SNAPBACK}>

It would be much clearer. The general idea with using one LED is that it'll fit into the cable gland of an XLR.

<{POST_SNAPBACK}>

 

 

Brian

 

You could use 3mm LEDs, I have a very useful little phantom power tester made that way.

 

Brian

 

( sounds like too many Brians- might spoil the broth)

[ben.suffolk]

Brian, could the problems of differentiating between the colours of the LED be solved by using two separate LEDs. Then would you not be able to see fairly well?

<{POST_SNAPBACK}>

It would be much clearer. The general idea with using one LED is that it'll fit into the cable gland of an XLR.

<{POST_SNAPBACK}>

 

I got round to building one today, as I had a bit of spare time on my hands. Following on from your comments about differentiating between the colours, I made it with 2 LEDs instead. I found that if I removed the cable gland I could 2 x 5mm LEDs to fit ok. I set them in hot glue to make sure they didn't move around. I guess expoy resin would be better, but I didn't have any to hand.

 

http://dmxprojects.com/images/dmx_tester.gif

 

I have not tested it as I'm at home, and my Desk is not. So I shall go and test it later, but since Brian tested the circuit design I see no reason why it won't work.

 

Steve if you have not yet got a tester sorted out, PM or email me with your address, and since I don't actually need it, I'll stick this one in the post to you.

 

Ben

 

Edit: Change the img url as I moved the server

[ziggyP]

The best and most robust is the Goddard Design DMXster, but also a bit bulky.

 

2nd best is the Chamtech X buster the same size as a Fluke DVM and cheaper than Goddard and Artistic, does every thing the others do plus a neat moving light test function with large library.

 

Ziggy

[sebew]

Does anyone have any idea what spec LED's to use? Am I right in thinking is +12 to -7v protocol?

[Tomo]

Does anyone have any idea what spec LED's to use? Am I right in thinking is +12 to -7v protocol?

<{POST_SNAPBACK}>

The spec of the LEDs is essentially irrelevant - any 'normal' LED will work fine.

 

The driving voltage only determines what current-limiting series resistor to use (except in the case of LED-modules which already have the resistor).

 

If you want something ultra-hyper-megabright like a Luxeon or the ones Osram were demoing at the AC Lighting show, then forget it as the desk won't be able to source the current!

[five_pin_xlr]

how can you tell where to put which colour LED??

 

I have red and green LEDS, 1 5pin connector and 2 270OHM resistor.

 

Help would be very much appreciated.

 

best regards

 

alex

[paulears]

I don't understand? Where to put the leds? - oh and why 2 x 270 ohm resistors. with just three components, I don't quite understand where the snag is, can you explain?

[five_pin_xlr]

I found on a website, that 2 x 270OHMS resistors and 2 leds for the tester, I am making a 5pin one. If this is totally wrong, then please advise. All I want is to make a tester that goes red for error in DMX green for good DMX signal.

 

Best Regards

alex