How to control the brightness of a LED using PWM?

Status
Not open for further replies.
R

Rooftop

Full Member level 2
Joined
Oct 28, 2004
Messages
134
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,298
Activity points
1,241
Designing led with PWM

Hi all,

i have 8*8 led and with that i want to display an alphabet(with scanning) so how to control the brightness using PWM?
Someone have idea?
 

Re: Designing led with PWM

In standard application you select a row and then a column and LED located at the row/column address will be on.
Now, if you modulate one of these signals with PWM (the PWM frequency has to be higer then the scanning frequecy, say 10:1) you will be able to control brightnes of the LED array.
 

Re: Designing led with PWM

Thanks for the reply.
I using db25(paralel port to access the led) Do you have some idea how to use pwm(It's like sampling a square signal right?)
I use control signal (C0,C1,C2) for the scanning.
Thanks
 

Re: Designing led with PWM

Rooftop said:
Thanks for the reply.
I using db25(paralel port to access the led) Do you have some idea how to use pwm(It's like sampling a square signal right?)
I use control signal (C0,C1,C2) for the scanning.
Thanks
Click to expand...

That is right. The faster the switching the more brighter the LED become.
The slower the less brighter it becomes. But if to slow then youre LED will show a flash.

For access turn the port line on and off. |_|-----|_| long |_|-|_| short.
The short should be the less brightess. Just remember to make the off period not to long.
This will show a flash.

:sm35:
 

Re: Designing led with PWM

Yay... thanks for the repply,now i will try it
 

Designing led with PWM

use a sine wave to control the light,I think like this.
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…