Hi there! Built simple circuit (arduino powering 12v .25 mA leds using uln2003 transistor arrays) that works with short wire from led to circuit board. But when I extend wire length I get fair amount of noise - LED never fully off.

Im using 18awg 2 conductor stranded hookup wiring with rca connectors at microcontroller.

How can I alleviate noise? I was reading about placing a capacitor at my DC power supply (12v, 5A). Would that help, and if so what kind?

Also thinking about using shielded wire, but then I would have to ditch rca connectors (would now need three terminals for drain, +12v, and collector pin) correct?

Thank you for your help ! For show coming up in a week

 

At what connection are you extending the wire?

 

using uln2003 transistor arrays

how - the datasheet shows a limit for simultaneous parallel ON for your LED current assuming it's 250mA not the barely visible 250µA for low voltage leds
the I/O delay for these transistors is up to 10µs e.g about 25kHz speed limit (with short connections)
. . .
if your connection cable is lengthy you may need to protect your LEDs with diodes against reverse voltage spikes there (in 1 random configuration i used 10nF capacitors . . . not sure if they suit everywhere)

 

At what connection are you extending the wire?

Hi there, Im extending wire from ends of LED to circuit board....

 

Hi there,

how - the datasheet shows a limit for simultaneous parallel ON for your LED current assuming it's 250mA not the barely visible 250µA for low voltage leds
the I/O delay for these transistors is up to 10µs e.g about 25kHz speed limit (with short connections)
. . .
if your connection cable is lengthy you may need to protect your LEDs with diodes against reverse voltage spikes there (in 1 random configuration i used 10nF capacitors . . . not sure if they suit everywhere)

Hi there,
I dont fully understand your first paragraph. If it helps to clarify, the LEDS are not fully on when at rest, but dimly lit - the full 250 mA is not being passed through.

 

Hi there, Im extending wire from ends of LED to circuit board....

That normally shouldn't cause a problem.
Try connecting a 0.1μF from the LED lead to common.

 

I may try the diodes. How do I wire them to the LED?

 

I should add, there are 4 huge radio towers right outside my windows. Could this be a situational issue???

 

That normally shouldn't cause a problem.
Try connecting a 0.1μF from the LED lead to common.

So, to be sure that mean a capacitor from negative of led to ground, not collector right?

 

So, to be sure that mean a capacitor from negative of led to ground, not collector right?

You'll have to post a circuit schematic before I can answer that.

 

You'll have to post a circuit schematic before I can answer that.

Okay, Ill try to get somethin up. An update: the noise disapears when I lift the cable off the ground. Maybe some power strips or AC cords are bugging it. Either way, its gonna be off the ground for the show...

 

http://www.wayjun.com/Datasheet/Led/1W%20High%20Power%20LED.pdf
Wayjun Technology Co.,Ltd www.wayjun.com Design and Application

1. in the ratings to be used within the operating LED current limit function of the resistor. How much resistance will have to refer to the specific product specifications required to calculate the rated current plus that.
2. LED to be used in parallel mode, each LED channel by adding resistors are required, must not be led directly to multiple parallel.
3. circuits shall be designed to note: When the LED goes out to prohibit reverse voltage.
4. circuitry required to design note: the lights, turn off the lights when you prevent the instantaneous voltage. 1W High Power LED
5. solder direction (electrode direction) to be orthogonal with the direction of PCB.
6. high temperature will reduce its performance and reliability, please stay away from heat sources.

i'm not sure i fully decode 3. 4.
as for 3. the reverse voltage is cancelled by same direction series (a high reverse blocking voltage) diode AND/OR reverse parallel diode

 

http://www.wayjun.com/Datasheet/Led/1W%20High%20Power%20LED.pdf
Wayjun Technology Co.,Ltd www.wayjun.com Design and Application

1. in the ratings to be used within the operating LED current limit function of the resistor. How much resistance will have to refer to the specific product specifications required to calculate the rated current plus that.
2. LED to be used in parallel mode, each LED channel by adding resistors are required, must not be led directly to multiple parallel.
3. circuits shall be designed to note: When the LED goes out to prohibit reverse voltage.
4. circuitry required to design note: the lights, turn off the lights when you prevent the instantaneous voltage. 1W High Power LED
5. solder direction (electrode direction) to be orthogonal with the direction of PCB.
6. high temperature will reduce its performance and reliability, please stay away from heat sources.

i'm not sure i fully decode 3. 4.
as for 3. the reverse voltage is cancelled by same direction series (a high reverse blocking voltage) diode AND/OR reverse parallel diode

http://www.wayjun.com/Datasheet/Led/1W%20High%20Power%20LED.pdf
Wayjun Technology Co.,Ltd www.wayjun.com Design and Application

1. in the ratings to be used within the operating LED current limit function of the resistor. How much resistance will have to refer to the specific product specifications required to calculate the rated current plus that.
2. LED to be used in parallel mode, each LED channel by adding resistors are required, must not be led directly to multiple parallel.
3. circuits shall be designed to note: When the LED goes out to prohibit reverse voltage.
4. circuitry required to design note: the lights, turn off the lights when you prevent the instantaneous voltage. 1W High Power LED
5. solder direction (electrode direction) to be orthogonal with the direction of PCB.
6. high temperature will reduce its performance and reliability, please stay away from heat sources.

i'm not sure i fully decode 3. 4.
as for 3. the reverse voltage is cancelled by same direction series (a high reverse blocking voltage) diode AND/OR reverse parallel diode

Hi there, thanks for this.
I maybe see the confusion...Im not wiring multiple LEDs to each collector pin of the uln2003 (the bold font talks of wiring leds in parallel). I have one 250mA led per collector, that is all. The uln2003 is rated at 500mA per collector so its good.

As stated, when led cable is lifted off the floor my problem disappears. Im guessing its to close to other strong AC power sources ?

 

For anyone curious, yes - it was the radio towers near my studio that caused so much extra noise. In the gallery space, all was well.
Thanks for the help as always!
here is some documentation: https://www.instagram.com/p/BL30wvSBRdp/?tagged=maxabeles&hl=en

Best,
-M