- #1
Meseria
- 16
- 0
Hello everybody,
I tried to make a special LED I <3 you gift for my girlfriend and it seems that I failed to take into account the battery discharge curve. I was using 50 red LEDs that I originally measured with my voltmeters LED function at 1.7v.
With measuring LED voltage, is it better to create a small circuit with say, 9v battery, 1 LED and a 1k ohm resistor. Then measure the voltage on the anode and cathode of the LED? I did it this way and it seems like they were running between 2.0 and 2.2 volts at a pretty good brightness. The voltage should be constant and it is the mA value that determines how bright or dim it is, right? So, is this the best way to figure out typ forward voltage for an LED?
Anyways, i setup my light array with 10 parallel series of 5. I had a 22 ohm resistor. The whole ohms = 9v - 1.7(5) over .020 shot back 25 ohms. So I wire it all together and it isn't bright at all, its very dim! Now, this was using my voltmeters LED return of 1.7v, which I think is incorrect.
So did I mess up in that I need to measure the typical voltage of the LED at a load? That gave me a bit higher in the volts dept.
My Energizer 9v's discharge curve seems to go from 9v to about 8.5 quickly, and then lowers to about 7.5 for quite a while before it is very close to dying. This is an alkaline battery. I have some NiMH rechargeable AA's and AAA's and they seem to start about 1.3, drop to 1.2 after a little bit and then stay at 1.2 until they are almost out. LEDs seem to have a very strict need for a constant source of voltage, so do I need to use batteries that have a discharge curve that is quite horizontal, like the NiMH?
I tried to make a special LED I <3 you gift for my girlfriend and it seems that I failed to take into account the battery discharge curve. I was using 50 red LEDs that I originally measured with my voltmeters LED function at 1.7v.
With measuring LED voltage, is it better to create a small circuit with say, 9v battery, 1 LED and a 1k ohm resistor. Then measure the voltage on the anode and cathode of the LED? I did it this way and it seems like they were running between 2.0 and 2.2 volts at a pretty good brightness. The voltage should be constant and it is the mA value that determines how bright or dim it is, right? So, is this the best way to figure out typ forward voltage for an LED?
Anyways, i setup my light array with 10 parallel series of 5. I had a 22 ohm resistor. The whole ohms = 9v - 1.7(5) over .020 shot back 25 ohms. So I wire it all together and it isn't bright at all, its very dim! Now, this was using my voltmeters LED return of 1.7v, which I think is incorrect.
So did I mess up in that I need to measure the typical voltage of the LED at a load? That gave me a bit higher in the volts dept.
My Energizer 9v's discharge curve seems to go from 9v to about 8.5 quickly, and then lowers to about 7.5 for quite a while before it is very close to dying. This is an alkaline battery. I have some NiMH rechargeable AA's and AAA's and they seem to start about 1.3, drop to 1.2 after a little bit and then stay at 1.2 until they are almost out. LEDs seem to have a very strict need for a constant source of voltage, so do I need to use batteries that have a discharge curve that is quite horizontal, like the NiMH?