# TC 421 problem



## Kamilstrom (Oct 18, 2012)

Hey everybody, I have modified TC 421 and need 6 channels(I know TC 421 have only 5)so when I try put my white xm-l2(24 leds in 2 strings -12 leds each thru 2 MW 1200 H with MW SE-350-48 supply)on same channel they'll start flash or not work at all. If I connect one string only, then works fine. Other channels I'll need for colors. It's anything what I can do?


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## jeffkrol (Jun 5, 2013)

Sound like the power supply is going in limp mode for some reason short, or overheating is the usual reason but there are others..
You run LED per series string.all led powered in parallel..

TC-420 is only a 5V PWM (very low current) signal to the LDD PWM circuit..

Can you roughly draw out what you have?
First swap the strings to make sure one isn't shorting somewhere..


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## Kamilstrom (Oct 18, 2012)

Hello Jeff, I forgot to mention about XM-L2 led are solderless and I do feed TC 421 with 12V 2A supply not thru screws(from right side) but from power connector on the left side. I'm using MW SE 350-48 connected to Steve's Ldd driver array(for 8 drivers). I have 2 LDD 1200H a 4 LDD 700H. If I connect those 2 white strings separately, at two different channels they work just fine. If I connect pwm signal from TC 421 on left string and then on right string it's work too, but not together if I split pwm signal. So...i think if Ldd-H take 3.3V and TC 421 put out only 5V it's not enough for 2 drivers(6.6V)? 
I have picture just before I connect XM-L2 together....


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## jeffkrol (Jun 5, 2013)

Humor me.. make sure both sides of Steves board has power input..
Just run another set of parallel wires to it from the power supply..


The PWM output of th tc-420 is on/off.
The Ldd can use any pwm voltage between 2.5 to 6v..
The current drain by the LDD is very small.
The tc-420 should be able to output 20mA-40mA


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## Kamilstrom (Oct 18, 2012)

Yes driver array has power on both sides. The same thing happens if I'll connect two different string of the color ones. I tried today measure V at pwm output with 1 driver connected is 2.49V with 2 driver is 1.99V.


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## jeffkrol (Jun 5, 2013)

Voltage will vary w/ duty cycle.. Need to be at 100%

Anything other than 5V @ 100% (or close) means they may have changed specs..though 3.3V or 5V is really the only normal options
for voltages at the gate pin.

Most meters average so you'd normally see like 2.5V @ 50 % duty cycle but it's really 5v..
you need to measure voltage at 100% on.


For the double channel up the gauge of your wire.. May be getting some voltage drop.
I prob. wouldn't desolder, just lop it off at the tc-420 and splice it in..
going to ruin your nice wiring job though.. 

sorry, It's not making much sense in my book atm..

you could check the current of the gate wire as well should be 40mA or so.
check at the driver board.
OPP's varies by load on the Ldd.. May not help..


> 2.) The current draw for the PWM pin is 5ma @ 100% on average. Because of this, I would not recommend driving more than 6 LDD's per arduino pin. 40ma is the maximum per I/O pin according to the folks at Arduino CC.


Most Aduino like setups like this "should" be able to handle multiple Ldd's w/ ease..

Not sure I'd run the PWM wires under the power supply though...Maybe EMF..

hmm 421....not sure if it's slightly designed different (well besides the wireless) or not..


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## SpringHalo (Oct 13, 2017)

I remember having issues with my own 8x Steve's driver board and a TC420. I believe the issue stemmed from the pull-down resistors being too small for the TC420 signal outputs to handle, so I removed the resistors and all was well.

The resistors are there to keep the lights from turning to 100% brightness when you turn on the LED power without having the controller on, but that only happens for the first ~2 seconds after power-up. Try removing one of the resistors on the LED-DRIVER board's affected channel and see if that makes a difference.


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## Kamilstrom (Oct 18, 2012)

When I measured that the light was on 95%. 
I guess I'll need different pmw controller HurricaneX or Bluefish mini (Storm is out of stock and Coralux is away until mid Aug-who knows what's going on) which is better? 
So I thought, will be any difference if I use instead that 12V 2A supply for TC 421 rather buck converter(48V to 12V)?

Well... I did pull out (can't locate those transistors yet)one driver for the xm-l2 from array and connected pins and everything work just fine "Eureka" look like you got it👍
Where I can find those transistors,please?


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## SpringHalo (Oct 13, 2017)

Kamilstrom said:


> Well... I did pull out (can't locate those transistors yet)one driver for the xm-l2 from array and connected pins and everything work just fine "Eureka" look like you got it👍
> Where I can find those transistors,please?













Assuming they haven't changed the design, the resistors are here. De-solder one or two of them next to the input you're trying to double and it should work dandy.


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## jeffkrol (Jun 5, 2013)

SpringHalo said:


> Assuming they haven't changed the design, the resistors are here. De-solder one or two of them next to the input you're trying to double and it should work dandy.



expect the unexpected....Think I remember this but didn't see the solution.


OR someone else also had Steves board problems.. 

Another reason to push RapidLED jumpered boards.. 

not sure how you figured that one out... 

It was my understanding that they were there for controller failure.. to save reeefers from 100% out..
still were a big PIA when I first started building..


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## Kamilstrom (Oct 18, 2012)

My look like this. So they are on same place like those at your picture, right?


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## SpringHalo (Oct 13, 2017)

Kamilstrom said:


> My look like this. So they are on same place like those at your picture, right?



Looks like they reduced the size of them, but they're still in the right place. Can you measure either side of one resistor with your multimeter in "ohms/resistance/Ω" mode? I'm curious if they changed the value. You can still go ahead and remove one. With stuff that small you can just blob a bunch of solder on it and the whole thing will come off.


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## Kamilstrom (Oct 18, 2012)

I will try measure that and I'll let you know. So far, thank you both very much...👍


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## Kamilstrom (Oct 18, 2012)

I measured resistance for you, when was resistor on the array, resistor value was 10.06Ω after removal was 11.86Ω.
Interesting was that when I removed only one( that one for the white string) another string(colors)stop working, so I removed all resistors, now it should be all right...


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## jeffkrol (Jun 5, 2013)

Normally is 10 Kilo ohms.


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## Kamilstrom (Oct 18, 2012)

Yes, setting was set at 20 Kilo ohms so measuring was 10.06Kilo ohms and 11.86Kilo ohms, sorry my mistake...


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