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Say watt??

CMB-24D channel config/settings

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Say watt??    5

Can the CMB-24D be used as 24 independent DC channels? If so, can I mix independent channels and RGB on the same controller? From what I have read here and on LOR's website it looks to be as simple as a channel setting in SE, but was hoping someone can confirm. Thanks - Gary

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mpageler    55

I'm running several cmb24d's with a combinination of dumb (1 channel) and rgb channels. 

To connect dump lights to separate channels, connect each negative light wire to one of the connectoirs labelled 1 through 24.  The positive light wires can go into any of the cmb24d outlets labelled as positive...doesn't matter which one.  You can also put several positive light wires into a single cmb24d positive output.

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Say watt??    5

Perfect! So I assume an independent DC channel on one of these controllers will look and sequence the same as a channel on an AC controller. I'm mainly concerned about being able to set the max intensity for the single channels. Ducks, this might be what you were referring to. 

I plan to run 12 VDC to each bank on the boards and would like to reduce the intensity to roughly 20%, to obtain an output of around 2.5 volts per channel. 

Sound reasonable? 

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TheDucks    28
16 hours ago, Say watt?? said:

Perfect! So I assume an independent DC channel on one of these controllers will look and sequence the same as a channel on an AC controller. I'm mainly concerned about being able to set the max intensity for the single channels. Ducks, this might be what you were referring to. 

I plan to run 12 VDC to each bank on the boards and would like to reduce the intensity to roughly 20%, to obtain an output of around 2.5 volts per channel. 

Sound reasonable? 

Huh? 2.5V.  12V LED strings usually group a few (typ 3) LED chips in series. Are you using 5V LEDS and trying to 'fake it'? Don't! Stray Voltage spikes will kill them in the end.

And I will differ from mpageler and say USE the Plus for that (RGB) bank as it is fused to protect the 3 drivers that it serves

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k6ccc    499
16 hours ago, Say watt?? said:

Perfect! So I assume an independent DC channel on one of these controllers will look and sequence the same as a channel on an AC controller. I'm mainly concerned about being able to set the max intensity for the single channels. Ducks, this might be what you were referring to.

The DC controllers from a sequencing point of view are identical to the AC controllers. 

16 hours ago, Say watt?? said:

I plan to run 12 VDC to each bank on the boards and would like to reduce the intensity to roughly 20%, to obtain an output of around 2.5 volts per channel. 

Sound reasonable? 

You want 20%, you set to 20% in your sequence - just like an AC controller.  HOWEVER!, your statement about an output of 2.5 volts raises the hair on the back of my neck.  Not how it works.  The lighting dimmers (both AC and DC (although they do it differently)) all operate with pulse width modulation.  What that means is that when you set a channel to 20%, the voltage is still whatever your source is (12 V in your case), but it's turned on only 20% of the time.  The power is switched on an off hundreds or thousands of times per second (I don't remember the switching frequency of a CMB-24D).  If you are thinking that you can drive a 2.5 volt light by setting the channel to only 20%, you will likely cause the bulbs to fail very quickly.

 

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Say watt??    5

I'm actually using arrays of 3.5mm red LEDs. Their operating voltage is around 2.6. The issue is that I need to use a specific number of them per array. If I can get an output around 2.6 vdc, I can connect them in parallel and be able to add or subtract any number of LEDs without consequence. 

My experience with PWM is that the output will be proportional to the duty cycle as long as the TOTAL period is relatively short. So if the PWM frequency is high (kHz), an input voltage of 12vdc and a duty cycle of 50%, will result in an output of around 6 volts. The key here is the switching frequency, especially when driving an LED.

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k6ccc    499
4 minutes ago, Say watt?? said:

My experience with PWM is that the output will be proportional to the duty cycle as long as the TOTAL period is relatively short. So if the PWM frequency is high (kHz), an input voltage of 12vdc and a duty cycle of 50%, will result in an output of around 6 volts. The key here is the switching frequency, especially when driving an LED.

That may appear to be true if you are measuring it with an analog voltmeter - which can't keep up the pulse rate.  A digital volt meter will come up with radically different measurements depending on the PWM frequency, duty cycle, and the meter itself.  Put an O'Scope on it and you will see how that is NOT the case.

The normal way of driving LEDs for consumer level applications is to use a voltage dropping resistor.  By selecting the value of the resistor, you can make the current anything that you want with any drive voltage that you have available.  For example if you have a 12 volt source and a LED that has a voltage of 2 volts at the desired current of 10mA, the resistor needs to drop 10 volts with 10mA through it so you would want a 1,000 ohm resistor (R in ohms = volts / current in amps).  Note that doing it this way allows for the source voltage to move a bit without having a large effect on the current through the LED.

In our lighting world, MOST (not all) 12 volt strips have three LEDs in series with a resistor in order to use up more of the voltage resulting in less of the power turning to heat in the resistor.  Whereas 5 volt strips have a single LED in series with a resistor.

In our smart pixels, each LED or group of three (for 12 volt stuff) has an integrated circuit that intelligently drives the LED.

 

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TheDucks    28

The resistor or SERIES a set of identical arrays  (quantity 6 is about 13V @ 10ma) if you PARALLEL 10ma arrays, you Multiply the current (60ma)

 

BTW PWM of 12V, still puts 12V on the array (no resistor), just for a short period

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Say watt??    5

I agree that an oscope will indicate a pulse amplitude of 12 volts. That is what oscilloscopes are designed to do. However, a PWM output at a 50% duty cycle will be a stable 6 volts if the frequency is high enough (100+ Hz). This is the essence of how PWM works. Anything connected to the output will have an effective 6 volts applied to it, whether it's a motor, analog meter or an LED.

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