[SOLVED] LED Strip not lighting up

I've a single colored led strip and I am trying to run them with arduino with a TIP-122 transistor.

I am not sure why they're not lighting up when connected with transistor and arduino, if I connect them directly with power supply, they do light up successfully.

I've attached the connections with a fritzing diagram I made.

The power supply used outputs 12 V - 1.5A (It converts from AC voltage)
Led strip is 2.5 meters rated 12 V, 4.8 W/m.
So they draw 1 Amps

Resistor across Base and PWM pin is of 220 ohms.

I am using Fade code in Arduino IDE.

Are you wired up like this? Can't tell from your diagram.

First pin (Base) should be connected the the Arduino Digital Pin. That is used to turn on/off the transistor.
Second pin (Collector) connected to the power source positive side.
Third pin (Emitter) should be connected the to to the pin that you would like to turn on/off.

In your schematic the third pin (emitter) should be connected to the LED strip, not the second one.

Fredx:
First pin (Base) should be connected the the Arduino Digital Pin. That is used to turn on/off the transistor.
Second pin (Collector) connected to the power source positive side.
Third pin (Emitter) should be connected the to to the pin that you would like to turn on/off.

In your schematic the third pin (emitter) should be connected to the LED strip, not the second one.

Completely, totally wrong! You are describing a Darlington emitter follower or common collector configuration. In such a case, the output voltage will be approximately 1.4V less than the base voltage. The maximum base voltage is 5V when the Arduino output is set high. So the LED load will be driven with 3.6V. Hardly useful for a 12V strip.

You can test/verify your transistor circuit by taking that wire that's running to D9 and connecting it to 5V instead (5V, open circuit, 5V, open circuit, . . .).

[The Arduino has to be powered to have that 5V available of course.]

Fredx:
First pin (Base) should be connected the the Arduino Digital Pin. That is used to turn on/off the transistor.
Second pin (Collector) connected to the power source positive side.
Third pin (Emitter) should be connected the to to the pin that you would like to turn on/off.

In your schematic the third pin (emitter) should be connected to the LED strip, not the second one.

My, but you aren't scoring any goals here! :cold_sweat:

CrossRoads:
Are you wired up like this? Can't tell from your diagram.

Yes, that's how it's connected.

runaway_pancake:
You can test/verify your transistor circuit by taking that wire that's running to D9 and connecting it to 5V instead (5V, open circuit, 5V, open circuit, . . .).

[The Arduino has to be powered to have that 5V available of course.]

Okay so I should connect the base of transistor with 5V Pin in Arduino with the 220 ohms resistor and leave the rest of the circuit as is?

I will power on both the supply and the arduino and the LEDs should light up very dim, as far as I understand, to check the circuit. Is that correct?

Hi,
Can you please post the code you are using please?

Do you have your project on protoboard?
Can you post a picture of your project?

Thanks.. Tom.... :slight_smile:

The TIP 120, 121 and 122 are a family of NPN type darlington transistors. Any of them will work for your application while not the best choice as a switch they will work. You want things wired as shown below with the exception that in your case the load is your LED strip rather than the lamp shown in the below image.

Adjust your base resistor and Arduino DIO pin accordingly, the pin acording to your code.

A TIP 120, 121 or 122 should have a TO220 case like shown in the image. Your original image looks to have something with a TO92 case maybe?

Ron

TomGeorge:
Can you please post the code you are using please?

Do you have your project on protoboard?
Can you post a picture of your project?

Thanks, Yes, here's the code (this time I used a simple ON instead of fade)

void setup()
 {
  pinMode(9, OUTPUT);
}

void loop() 
{
  digitalWrite(9, HIGH); 
  delay(1000);                       
}

It's on a breadboard.

I've attached the connections photo here, though it's not clear, but it's connected the same way as in the fritzing diagram in post 1.

Ron_Blain:
The TIP 120, 121 and 122 are a family of NPN type darlington transistors. Any of them will work for your application while not the best choice as a switch they will work. You want things wired as shown below with the exception that in your case the load is your LED strip rather than the lamp shown in the below image.

Adjust your base resistor and Arduino DIO pin accordingly, the pin acording to your code.

A TIP 120, 121 or 122 should have a TO220 case like shown in the image. Your original image looks to have something with a TO92 case maybe?

Ron

I am not sure which package is my transistor, how should I find it out? And yes my wires are connected exactly as that image shows.

Your image looks to be a TO220 case and if you have it like the drawing I posted it should work. That assumes your polarities are correct. In my image, as drawn, left to right the transistor pins are Base, Collector and Emitter. Your LED strip should have 12 volts (+) applied and you are switching the (-) side using the transistor.

You can move the base resistor to +5 volts and see if the LED strip turns on. That's the idea of driving pin 9 high.

Ron

Or you can always go with the relay , although making the LEDs fade would then be problematic.

Look here

Hi,
Thanks for the pics and the closeup of the transistor connections.
With that code running the LEds should be ON all the time.
Do you have a DMM?

If not do you have an LED and say a 1K or 470R resistor?

Did you try moving the pin9 end of the jumper off pin9 and connect it to 5V, so that the base has current flowing from 5V through the 220R?

Thanks.. Tom.. :slight_smile:

Ron_Blain:
Your image looks to be a TO220 case and if you have it like the drawing I posted it should work. That assumes your polarities are correct. In my image, as drawn, left to right the transistor pins are Base, Collector and Emitter. Your LED strip should have 12 volts (+) applied and you are switching the (-) side using the transistor.

You can move the base resistor to +5 volts and see if the LED strip turns on. That's the idea of driving pin 9 high.

Ron

Understood, thanks, I tried connected the base with resistor accross 5V pin and still no luck. By the way, if they do not light up in 10 seconds I turn off my power supply. Does the circuit need time to get saturated or something?

Fredx:
Or you can always go with the relay , although making the LEDs fade would then be problematic.

Look here

Thanks, I can't use a relay because eventually I am going to make these LEDs sound reactive so only this cricut can do that.

TomGeorge:
Hi,
Thanks for the pics and the closeup of the transistor connections.
With that code running the LEds should be ON all the time.
Do you have a DMM?

If not do you have an LED and say a 1K or 470R resistor?

Did you try moving the pin9 end of the jumper off pin9 and connect it to 5V, so that the base has current flowing from 5V through the 220R?

Thanks.. Tom.. :slight_smile:

Thanks, Yes I have a digital multimeter, LED, and yes I do have a 470 ohms resistor also. Are we going to test our circuit with a smaller led?

Yes I did try to move the jumper from pin 9 to the 5V pin, and still no luck. By the way, I turn off the power supply in 10 seconds if the lights don't light up, do I need to give them some time to saturate or something?

UPDATE - Please see next page.

UPDATE - Thanks Tom for giving me the idea of multimeter, I used it's connectivity feature to check my wires and turns out one male to male wire was not working.
This was my first time using a transistor and external power supply so I thought I am doing something wrong hence I posted here, sorry.
And my sound reactive LED strip project through realtime android mic values with HC-05 is finally complete, thank you everyone.

Glad it all worked out and came together for you.

Ron