LED driver question

newleduser

Joined Feb 21, 2021
3
New user question. Using a 64 LED grid [homemade] as a simple signal light {all leds to light up at once, from an existing controller} I'm using a separate power source [the controller does not supply enough power] My question is what driver would handle this?

SamR

Joined Mar 19, 2019
3,392
Welcome to AAC! Since it is homemade, how about posting a circuit schematic so we can have something to work from?

MisterBill2

Joined Jan 23, 2018
8,711
The driver will depend on the load voltage and current. 64 LEDs in series might draw half an amp or less at about 180 volts, if they are the super bright white ones that I have worked with. So we need to know the voltage and the current to provide an answer any better than a guess.

Audioguru again

Joined Oct 21, 2019
3,171
I would guess that the 64 LEDs are all in parallel and might even have different colors. Maybe the LEDs are connected with backwards polarity.
Maybe the unknown power controller and unknown power source are burned out.

MisterBill2

Joined Jan 23, 2018
8,711
No matter what, we still need to know the connection arrangement of the LEDs and what voltage and current the grid array is intended to use. We also need to know the voltage from that "separate power source" and what sort of output the controller is able to provide. And also, are all of the LEDs the same kind? So there are still a lot of important things for us to know. I would not need any circuit drawing if those answers are available.

newleduser

Joined Feb 21, 2021
3
No matter what, we still need to know the connection arrangement of the LEDs and what voltage and current the grid array is intended to use. We also need to know the voltage from that "separate power source" and what sort of output the controller is able to provide. And also, are all of the LEDs the same kind? So there are still a lot of important things for us to know. I would not need any circuit drawing if those answers are available.
Series wired. 16v power (but this could be changed) two arrays are all white, a second is all green and a third is all red. No more than two can come on at the same time. No array lights for more than 2 seconds, +or - (controlled by the device that has the controller chip. which has a power output of 5v "on" and zero volts "off". This device really just sends the signal and provides a mini DIN 6 position female jack to connect the arrays) The DIN only uses 5 of the 6 pos. ,one is a ground and the others go to to the "mystery" driver"

MisterBill2

Joined Jan 23, 2018
8,711
If the power source is 16 volts, since white LEDs that I am familiar with take just a bit over 3 volts, that says 4 white LEDs in each series string, along with a current limiting resistor to set the current as desired. Green LEDs take a lower forward voltage so there could be six or possibly seven of them in each series string, again with a suitable series resistor to set the current. Red LEDs with less than 2 folts forward voltage can be 8 in each series string, plus a resistor for each string, similar to the others.
The control transistor for each array will be an NPN type with the emitter tied to power common negative and the collector tied to the negative side of each array. Each base connection will be fed by one output from the mystery controller, with a series base resistor sized to keep the base current well within saturation at the anticipated collector current. So there will be a bit of math required in calculating all of those resistors, but since the voltage drop needed and the current are known it will not be hard to do.

Audioguru again

Joined Oct 21, 2019
3,171
Dim old green LEDs were about 2.2V each.
Very bright modern green LEDs are made with the same chemistry as blue and white LEDs so they are about 3V to 3.6V each.

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Papabravo

Joined Feb 24, 2006
16,086
Series wired. 16v power (but this could be changed) two arrays are all white, a second is all green and a third is all red. No more than two can come on at the same time. No array lights for more than 2 seconds, +or - (controlled by the device that has the controller chip. which has a power output of 5v "on" and zero volts "off". This device really just sends the signal and provides a mini DIN 6 position female jack to connect the arrays) The DIN only uses 5 of the 6 pos. ,one is a ground and the others go to to the "mystery" driver"
Is there some reason you think a verbal description is some kind of adequate substitute for a SCHEMATIC diagram?

MisterBill2

Joined Jan 23, 2018
8,711
Is there some reason you think a verbal description is some kind of adequate substitute for a SCHEMATIC diagram?
YES! I don't have the setup to deliver a nice schematic any more, a direct lightning hit took care of that. And many folks have adequate visualization abilities to understand a circuit description. Besides that there are folks often present here who are quite able and willing to produce an accurate circuit drawing from a verbal description. And one more thing is that a verbal description works for those who lack excellent vision.
That recently delivered description was a bit ooff because I was not familiar with the forward drop of the much higher output green LEDs. So they would use the same arrangement as the white ones.
SORRY ABOUT NOT BEING TOTALLY CORRECT, Folks.

newleduser

Joined Feb 21, 2021
3
To all who have thoughtfully and helpfully made suggestions, on my original post: Thank you and I have solved my problem, by reducing the number of LEDs to 48; making the arrays myself. I am handy with much of the processes, but pretty ignorant of the foundations many of you already have...but I'm learning rapidly. Next project. I will provide much more detail, before asking advice.
thanks again

MisterBill2

Joined Jan 23, 2018
8,711
Often times, the effort to completely define the requirements and problems of a project helps a lot towards finding the solutions.