Hello - I’m having an issue I was hoping someone could help me with. I’m attempting to setup five LED’s (https://www.sparkfun.com/products/13104) in series to be driven by the femtobuck LED driver (https://www.sparkfun.com/products/12937). Pretty much the same setup as the last “Ask Pete” episode.
Anyhow, when I wire them in series (positive in to the first LED and then the negative from the first LED into the positive of the second and so on) and plug a power supply in that supplies 12V 3A; the LED’s barely come on. I’ve tested the LED’s separately using a bench-top power supply and I’ve verified conductivity between each LED using a multi-meter, but can’t figure it out. The only thing I can think of is that the gauge of my wire is to big. I was just re-purposing what I had around the house so I used some wire left over from wiring trailer lights.
Any help would be appreciated. I don’t want to scrap the project just cause I hit a wall. Please let me know if there is more information required.
Your supply is not providing enough current. For 5 LEDs @ 750mA, that’s 3.5A… What supply are you using? It may be rated at 3A but it’s not putting out that much… What’s your bench top rated for? If it’s rated for more, than use the bench top to supply power to the LEDs… This way you could see exactly what the LEDs need to operate correctly.
How are you connecting the buck? What is the signal you are sending them for the brightness?
Those LEDs should become bright long before they reach 750mA. And your wire shouldn’t be too big. But what size are we talking about? If you’re using <4 gauge, then yea it’s probably too big…
Also the voltage drop on those LEDs are at least 3.2V, which means 12V isn’t enough either. Try just putting 3 LEDs in series.
Ok, thank you. I guess I need to read up on voltage and wiring in series. I guess I’m a little foggy on the issue.
I took a 19.5V power supply from a laptop and it powers them without issue.
I appreciate the response and the kick in the right direction.