# pulse width modulation

#### 016chris

Joined Oct 30, 2007
5
i am trying to make a dimmer switch circuits using pulse width modulation to dim a 5 volt lamp. The circuit needs to be powed by AAA bateries and power a 5 volt lamp. Can any one recommend any good sights to look for one or email me a good circuit

#### iONic

Joined Nov 16, 2007
1,654
Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance. For a supply voltage V,

* Light output is approximately proportional to V
* Power consumption is approximately proportional to V
* Lifetime is approximately inversely proportional to V 16
* Color temperature is approximately proportional to V 0.42

Not that you need all this info. There are a gazillion sites dealing with PWM and lighting.

You might want to study the data sheet for the LM555 Timer. http://cache.national.com/ds/LM/LM555.pdf in particular the monostable mode.

#### GS3

Joined Sep 21, 2007
408
* Light output is approximately proportional to V
* Power consumption is approximately proportional to V
* Lifetime is approximately inversely proportional to V 16
* Color temperature is approximately proportional to V 0.42
The first one is notoriously false. I went to Wikipedia to check and saw you copied from there but left out the exponents.
http://en.wikipedia.org/wiki/Light_bulb

Light output is approximately proportional to V^3.4
Power consumption is approximately proportional to V^1.6
Lifetime is approximately inversely proportional to V^16
Color temperature is approximately proportional to V^0.42

#### beenthere

Joined Apr 20, 2004
15,819
With a five volt lamp, a pot changing base current into a transistor should be all the control necessary.

#### GS3

Joined Sep 21, 2007
408
With a five volt lamp, a pot changing base current into a transistor should be all the control necessary.
Except that the OP explicitly asks about doing it with PWM and also there is a question of using AAA batteries anda 5 V lamp which I am not quite clear about.

And then there is a question about "good sights" which I am not sure how to interpret.

#### beenthere

Joined Apr 20, 2004
15,819
I believe that might be "good sites".