Total newb here, so please excuse my misguidance but I am stumped as to what I am doing wrong here. My end goal with this project is to have multple LED panels flash in sequence (which i've written the code for already). Today I am wiring and soldering everything together and I am running into problems in regards to getting my arduino to switch my TIP 120 so that my LED panel flashes.
The power supply for the LED panel is 12V, 1A. I know the transistor works because I have tested them with simple transistor LED circuits that you see in most TIP 120 tutorial videos. I have connected the Collector past the load (LED panel) and the emitter past that down the circuit. I am using a 1KOhm resistor between the base and the arduino pin 8. In the picture I am posting the grounds were seperate.
A weird quirk I noticed (If I reverse the collector and emitter pins *Opposite of the picture) the LED panel turns on, but is not affected by the base pin and remains on continuously, What is causing this?
So you are saying that I should have a wire running from the emitter pin to arduino ground? Should I still have the LED Panel wire running to the LED power supply ground?
There can't be any base>emitter current without a return/ground to the Arduino.
There can't be any LED panel current without a return/ground to the LED panel supply.
Leo..
So, either it's not wired like the schematic, or you've got a bad or wrong component. Are you sure it's a 1K resistor?
Or, maybe your software isn't turning-on Pin-8?
Are you sure it's a TIP120? The TIP120 is a Darlington pair, and a regular transistor may not saturate with a 1K base resistor.
Have you tried it again with a regular-little LED (with the required current-limiting resistor)?
If you disconnect the LED panel from the transistor and ground that pin, does it turn-on?
Usually, a "blown" transistor will short-out and so the LED panel would be on all of the time, so if it won't turn-on it's probably not a fried transistor.
(Disregard the blue yellow and red LEDS, as they are part of another test circuit and not part of the circuit I am dealing with.)
Oh fantastic, what a way to ask for help. You still haven't got a common ground in that circuit.
So stop jerking us around, come clean. Post a picture of the circuit you are having trouble with, and only that. Until then you are a poster who is not to be trusted.
And stop posting pictures off site read the rules we stick to here.
Please read this:- How to use this forum
Also
Image guide image guide
So, either it's not wired like the schematic, or you've got a bad or wrong component. Are you sure it's a 1K resistor?
Or, maybe your software isn't turning-on Pin-8?
Are you sure it's a TIP120? The TIP120 is a Darlington pair, and a regular transistor may not saturate with a 1K base resistor.
Have you tried it again with a regular-little LED (with the required current-limiting resistor)?
If you disconnect the LED panel from the transistor and ground that pin, does it turn-on?
Usually, a "blown" transistor will short-out and so the LED panel would be on all of the time, so if it won't turn-on it's probably not a fried transistor.
I rewired everything based on my schematic and it worked! I went directly to the ground pin on my arduino instead of using the rail. Something definately got jumbled in my wiring! Thanks so much for the help!
Now here is the thing, I am not out of the water yet. The real LED panels I will be using are Metalux 2'x4' panels which run 120V, 40W, at .35A. Will my darlington TIP120 transistor still work with this? Also, another variable has been added to the equation.
The Light panel has three wires (Hot, Neutral and Ground), Which wire do I splice into and attach my transistor circuit? Don't neutral and ground pretty much do the same thing? How would I update my schematic to achieve this?
Grumpy_Mike:
Oh fantastic, what a way to ask for help. You still haven't got a common ground in that circuit.
So stop jerking us around, come clean. Post a picture of the circuit you are having trouble with, and only that. Until then you are a poster who is not to be trusted.
And stop posting pictures off site read the rules we stick to here.
Please read this:- How to use this forum
Also
Image guide image guide
That sounds like 120V AC. Do not connect any of those wire to the TIP120. Controlling 120V AC calls for an entirely different device. Perhaps a Solid State Relay (SSR).
digradom:
The Light panel has three wires (Hot, Neutral and Ground), Which wire do I splice into and attach my transistor circuit? Don't neutral and ground pretty much do the same thing? How would I update my schematic to achieve this?
Please post the spec/data sheet , link to where you purchased the panel.
I did a quick google and suspect your panel has a driver unit and it is AC.
groundFungus:
That sounds like 120V AC. Do not connect any of those wire to the TIP120. Controlling 120V AC calls for an entirely different device. Perhaps a Solid State Relay (SSR).
How would I go about controlling this panel? Surely there must be a driver inside of it much like a standard LED strip that turns the AC into DC (Since it uses LEDS). Maybe I would splice into there? If not, how would I go about controlling this panel with my arduino?
So I opened up the panel and Voila, there is a DC power supply attached. Here are the specs
Vout: 30-42VDC
Iout: 900mADC
That is well under the max voltage of the TIP120 which is 60V, and the curent is under the 1amp used in the previous.
So, stop me if i'm wrong, but I think I can just splice into the negative wire with my schematic from above and it should work fine? Am I missing something here?
Wawa:
Bad idea to use a TIP120 in the power line of the LED driver.
These LED drivers can be PWM-dimmed with the PWM pins of the LED driver.
Try an opto coupler, with collector to DIM(+) and emitter to DIM(-)
Drive the opto LED (with 1k current limiting resistor) from an Arduino pin.
Leo..
This sounds like a good solution. Another tidbit of information, is that the PWM+ and - are not connected to anything, which means the circuit and light can function without any power going through those circuits.
I don't have any optocouplers on hand and I need this done by tommorow, so I went ahead and connected my current TIP120 configuration to the negative rail of the DC power supply. It worked, but I understand your concern about current jumping to the micro controller and potentially frying it. For my purpose, an optocoupler will work just as well as a switch, correct?
Grumpy_Mike:
I would connect the PWM - to ground and feed a 10V PWM to the PWM+
What exactly is the control you are after, on / off or variable brightness?
My goal is to make these flash on and off in sequence with a couple other of these panels I plan on rigging up. There will be no dimming needed, so I am not sure if its neccesary to mess with the PWM pins? The panels say that the max dimming is 10%, so I am not sure if its worth hooking into the PWM.
digradom:
Another tidbit of information, is that the PWM+ and - are not connected to anything, which means the circuit and light can function without any power going through those circuits.
I know.
This type of driver pops up on the forum every now and then.
There probably is ~10volt between the two DIM wires of that LED driver (measure it).
You probably also can dim this LED driver with a >= 100k pot (as variable resistor), connected to those wires.
As well as switch off the driver by shorting the two wires.
Try connecting the two wires through a 10k resistor. You probably have a dim light.
Not sure how well isolated these DIM wires are from mains power,
therefore I recommend an opto instead of a galvanic connection.
Leo..
