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Windows 7: LED Dimming and Brightening

28 May 2010   #1
Lordbob75

Windows 7 Ultimate x64, Mint 9
 
 
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


My System SpecsSystem Spec
.

28 May 2010   #2
The Howling Wolves

Windows 7 Home Premium 64bit
 
 

Quote   Quote: Originally Posted by Lordbob75 View Post
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.
My System SpecsSystem Spec
28 May 2010   #3
kodi

Windows 8.1 Pro x64
 
 

Try to connect the LED's direct and not through the potentiometer
My System SpecsSystem Spec
.


28 May 2010   #4
mpcrsc562

Windows 7 Ultimate x64
 
 

Can you post a schematic?
My System SpecsSystem Spec
28 May 2010   #5
WindowsStar

Windows 7 Enterprise (x64); Windows Server 2008 R2 (x64)
 
 

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.
My System SpecsSystem Spec
28 May 2010   #6
A Guy

Microsoft Community Contributor Award Recipient

Windows 7 Home Premium x64 SP1
 
 

What is the voltage rating of the LED? What are the high and low range voltages when changing the fan speed pot? It may be they are indeed dimming, but it is a relatively small change. It may also be that the range is already near the brightest setting of the LED and therefore they are already almost fully bright even when the fan is turned all the way down. Just a thought. A Guy
My System SpecsSystem Spec
28 May 2010   #7
A Guy

Microsoft Community Contributor Award Recipient

Windows 7 Home Premium x64 SP1
 
 

Quote   Quote: Originally Posted by WindowsStar View Post
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.
LEDS can be dimmed, but I'm not sure this is true of ALL LEDS. The LED's intensity can be determined by the level of voltage being supplied. Or the LED's intensity could be controlled using pulse-width modulation (PWM). That is beyond me though.

A Guy

P.S. I'm a TV Tech BTW, mostly boards these days, lol. Newer LED lit LCD TV's have local dimming, very complex though.
My System SpecsSystem Spec
28 May 2010   #8
WindowsStar

Windows 7 Enterprise (x64); Windows Server 2008 R2 (x64)
 
 

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
My System SpecsSystem Spec
28 May 2010   #9
Lordbob75

Windows 7 Ultimate x64, Mint 9
 
 

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
My System SpecsSystem Spec
29 May 2010   #10
kodi

Windows 8.1 Pro x64
 
 

One wire from PSU to Pot to fan
Another wire from PSU to Resistor to led
My System SpecsSystem Spec
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 LED Dimming and Brightening




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