I built this simple color organ and swapped out the standard LEDs with 3.2-3.4v, 100-120ma LEDs. It worked pretty good, but then I decided to remove the resistors between the LEDs and they got a little brighter.

http://www.instructables.com/files/orig/FKQ/ZKWQ/GQ5PYWHF/FKQZKWQGQ5PYWHF.pdf

The weird thing is that the LEDs at the end get way brighter than the rest. I even tried removing the 2.2k resistor and swapping them out with 1k resistors.

http://www.instructables.com/file/FIEOAVUGQ5PWB21

I have made all the LEDs the same color, and definitely the ones to the right of the board light up quite a bit brighter than the rest.

Any ideas on how I can fix this to make them all equally as bright? I am using 12v.

Thanks!

Bryan

 

Increase the resistance of the resistor that is presently marked as 270R.

 

I am not looking to dim the ones on the right, but make the ones on the left brighter. There is a significant brightness difference.

Any other ideas?

 

The resistors that set the LED current (aka brightness) are the
100 ohm for the high channel
180 ohm for the mid channel
270 ohm for the low channel

To increase brightness you use a lower resistance value.

AND if they are all the same LED's and the same number of LED's in each channel then all 3 resistors should be the same rating to achieve the same brightness across all 3 channels.

 

I completely removed those resistors and put jumpers in their place, they definitely got brighter, but the far left ones are WAY dimmer than the others and definitely appear to be underpowered for some reason.

 

PUT THE RESISTORS BACK.. LED's MUST have current limiting resistors.

 

I understand this, but why would the LEDs be getting different amounts of current and how can this be fixed? Thanks for all your help in this, I really appreciate it.

 

You fix it by putting the resistors back into the circuit.

Without current limiting resistors each string will/can draw different currents based on slight differences in forward voltages/wire resistance,etc... thus causing 1 string to draw more current than the others. The resistors "set" the current to the value you want.

 

I see. So if I fiddle around with those, I should be able to get them equally bright?

 

I see. So if I fiddle around with those, I should be able to get them equally bright?

Yes those resistors set the current for each channel. Adjust them and brightness will adjust accordingly. BUT they must be there.. No "jumpers"

 

I see. So if I fiddle around with those, I should be able to get them equally bright?

I'm no expert witness, but check each/every, LED and resistor separately, then combine them to get the closest in equal brightness.

 

This is a frequency controlled circuit. The brightness of the high frequency section is controlled by how much high frequency energy is being put into the input. If you want all the LEDs to be the same brightness, play music that has the same amount of high frequency sounds as it has low frequency sounds.