Is this a good/stupid idea ? LED in //

[Jouellet]

Hi Folks,

I want to build a seven segment display, about 6" high. each segment will have approx. 8-10 LEDs.

LED that I'll be using are rated 3.2-3.4 volts, 30 mA. Supply voltage is going to be around 12 V

Normally, one should do the math, put a couple of LED in serial, calculate the limiting resistor.

What if, I use a 3.3V regulator, and put all the LED of a segment in parallel ? That way, I would not need any resistor. Beside, 8-10 LED in // would be at worst 300mA: regulator I found (AMS1117-3.3) is good for 1 Amp (with good heatsink, I suppose). also, if incoming voltage fluctuate, let's say 10-12 volts, the actual brightness (using LED in serial) would normally vary, but being rectified to 3.3 V. I assume the brightness would be constant !

Thanks for advise !

 

[Gryd3]

Hi Folks,

I want to build a seven segment display, about 6" high. each segment will have approx. 8-10 LEDs.

LED that I'll be using are rated 3.2-3.4 volts, 30 mA. Supply voltage is going to be around 12 V

Normally, one should do the math, put a couple of LED in serial, calculate the limiting resistor.

What if, I use a 3.3V regulator, and put all the LED of a segment in parallel ? That way, I would not need any resistor. Beside, 8-10 LED in // would be at worst 300mA: regulator I found (AMS1117-3.3) is good for 1 Amp (with good heatsink, I suppose). also, if incoming voltage fluctuate, let's say 10-12 volts, the actual brightness (using LED in serial) would normally vary, but being rectified to 3.3 V. I assume the brightness would be constant !

Thanks for advise !

Each segment would be 300mA... 7 segment display would be 2.1A + the current for anything else you wish to add...
Additionally, LED's are not all equal, so there is a possibility that one of the leds in the segment will burn out. Use a current limiting resistor.

 

[hevans1944]

It is NOT a good idea. There is a resource here in this forum on how to drive LEDs. Do not connect the LEDs in parallel and attempt to drive them with a constant-voltage source!