LED Dimming and Brightening

Alright everyone, I can find no good reason for why this is occurring for me.

As some of you know, I am trying to make a fan speed controller. So far, I am successful, save for the LEDs.
I am using a 25Ohm potentiometer to control the fan speed, and that part works beautifully. The issue is that I want to use an LED indicator that glows bright at max speed, and is very dim at low speed.

I have the set up like this:
12V from PSU connected to the 25Ohm potentiometer (prongs 1 and 2 connected), then the Fan and LED (with 500Ohm resistor) in parallel.

The fan slows and speeds up as intended, but the LED does not change at all...

Can anyone help me out here?

~Lordbob

Lordbob75 said:

Alright everyone, I can find no good reason for why this is occurring for me.

As some of you know, I am trying to make a fan speed controller. So far, I am successful, save for the LEDs.
I am using a 25Ohm potentiometer to control the fan speed, and that part works beautifully. The issue is that I want to use an LED indicator that glows bright at max speed, and is very dim at low speed.

I have the set up like this:
12V from PSU connected to the 25Ohm potentiometer (prongs 1 and 2 connected), then the Fan and LED (with 500Ohm resistor) in parallel.

The fan slows and speeds up as intended, but the LED does not change at all...

Can anyone help me out here?

~Lordbob

Here's the man that can do it.
Attachment 75525

I couldn't help myself.

Try to connect the LED's direct and not through the potentiometer

Can you post a schematic?

I don't think you are going to get the result you want. LEDs typically are on or off they are diodes. Some LEDs can be driven harder to be brighter but making that kind of change would be a huge change for a fan. You will need to use an incandescent bulb to get the effect you are looking for. There are some very cool bulbs now-a-days that even look like a RED LED.

If you are talking about LED back lighting on LCD TVs they don't dim them. They turn some on and some off, the more that are on the brighter the less that are on the dimmer. They look like they are dimming because the light reflects off the backing and other LEDs.

O = on and o = off

OOOOOOO
OOOOOOO
OOOOOOO
OOOOOOO = all on bright

OoOoOoO
oOoOoOo
OoOoOoO
oOoOoOo = half on half off dimmer

ooOooOo
OooOooO
ooOooOo
OooOooO = very dim

It is a red LED, so between 1.8V and 2.2V. I cannot draw a diagram right now, but here is the best I can do:

12V in from PSU to
25Ohm potentiometer to
(500Ohm resistor to red LED) and fan

Does that help? The fan and (resistor and led) are in parallel.

~Lordbob

One wire from PSU to Pot to fan
Another wire from PSU to Resistor to led