DMXing LED's For a Big show

[TimG]

Hey All,

I am soon to be starting on panto for this year. I primarily run the sound and projections however, the producer has asked me to do a bit of pre-rigged lighting. The show is Peter Pan, so i am sure you will all know how tech heavy the show will be.

What I need help with is I need to put the LED's into the 1st 2 portals (not including the false pros) in each star. He wants them to twinkle (this can be in 'blocks' rather than individually) and all light up during the flight to Neverland. I have brought 450 ultra bright hard white 5mm LED's, i know i will need at least 8 cable connectors (as the portals are in 5 pieces each) but what else will I need?

Here is the shopping list I have so far:

450 Ultra Bright hard white LEDs

10 cable connectors

100-200 single core 0.5mm Copper cable

LED DMX Driver: (something like this: http://www.ebay.co.uk/itm/15A-XRL-3...ome_Garden_Lighting_Parts&hash=item1c3fd596f7 )

Also how many LEDs (Min/Max) can I put to a channel?

we only have 512 channels as its an old theatre.


Many Thanks

Tim

 

[dbaxter]

The write-up on that controller says 1 amp per channel, so you need to know the draw of one of the LEDs and divide. You may want to back off the result a little for a safety factor. Plus 27*1 is more than the 15 they say total, so the real limit for the board may be more like .55 amp/channel. Can't tell. You may also need more than 27 channels as the write-up talks about effects which could require their own channel in addition. Pretty nifty little controller, however. Tempted to get one myself - just in case. I don't envy you your wiring task ahead.

 

[TimG]

I believe the voltage is 3.2-3.8 V per LED, I will have to work it out sometime. I am planning on having 2 of the controllers, 1 per Portal hopefully. That should hopefully relive the draw on the power per channel. I'm not to worried about them running individually or twinkling properly ect, he is more interested in the surprise wow factor of the set all lighting up without using the normal up/down lighters.

I'm assuming I can have 3 sets of the LED's with one common wire rather than having RGB?

Yeah it will be a week or so of me in the warehouse with a drill, soldering iron and a electric fan and as soon as that task is finished i need to make the logo projection, prologue, all BG projections and possible other specials like pans shadow flying around the stage and Tinkerbell bouncing around the nursery.

So much to do and so little time.

 

[dbaxter]

You want the current draw, not the voltage, of the LEDs. For example, 20 LEDs that use 25 milliamps each at full bright is a total draw of .5 amp.

 

[TimG]

The LED Specs say they draw 20mA min and 30mA max, working from this i can have a maximum of 33 LED's per channel and 27 comfortably safely.

Assuming my calculations are right I can have 81 LEDs on 1 group which is 3 channels with 1 common wire and 729 on the 27 channel controller. This number seems really high to what I expected.

Are my calculations right or should I only use 1 set of 27 LEDs per common wire?

 

[TimG]

Just thought, would I need to get signal boosters as the signal will need to be sent a possible 30-40 ft around the portals.

 

[n1ist]

That controller has a constant voltage output that is PWM'ed for dimming. The output voltage will be whatever the input voltage is (less some rather small drop in the FETs). You will need current limiting on the LEDs or they will burn out.

You will make up series strings of LEDs (up to 5 or 6 if you are running on 24V, up to 3 on 12V) and a current-limiting resistor. Choose a resistor so the string will draw 20mA (Use one of the on-line LED resistor calculators to find the value). Then you can connect up to 25 strings in parallel (actually more, but I like to not push things to the max current) per channel. The number of channels needed depends on the effects you want.

The board doesn't care what color the LEDs are (just pick the right series resistors), so you can use all white instead of RGB.

/mike

 

[TimG]

That controller has a constant voltage output that is PWM'ed for dimming. The output voltage will be whatever the input voltage is (less some rather small drop in the FETs). You will need current limiting on the LEDs or they will burn out.

You will make up series strings of LEDs (up to 5 or 6 if you are running on 24V, up to 3 on 12V) and a current-limiting resistor. Choose a resistor so the string will draw 20mA (Use one of the on-line LED resistor calculators to find the value). Then you can connect up to 25 strings in parallel (actually more, but I like to not push things to the max current) per channel. The number of channels needed depends on the effects you want.

The board doesn't care what color the LEDs are (just pick the right series resistors), so you can use all white instead of RGB.

/mike

Thanks Mike, would I need to put a resistor onto each LED or just a string? how would I work our what resistors I need?

Thanks

Tim

 

[TimG]

I have worked out that the resistors i need are 680 Ohm 2W, as the Voltage per LED is 3.8V, Ampage is 30mA and input power will hopefully be 24V. Is this calculation right?
That calculation is for each individual LED I have just found an array calculator.

Thanks

Tim