Sooooooo been doing a little bit of electronics for a while. Never made my own devices just kits and repairing things.

Sorry if this has been posted 5 million times already but i'm sick of searching for an answer. I'm modding a laptop case and wanted to put pulsing leds in the keyboard and around the case 8 in total. I've got a pulsing circut going using a 555 but it will only power 1-2 LEDs i need to work out how to get it running 8 but the catch is it has to be small as possible! I'm using a smd components to save on space. Ive made a quick example for you to oogle. Any help would be awesome!

 

With 9V supply you should be able to power three or four LEDs connected in series.
Create three or two such strings of LEDs, each string driven by its own transistor.

 

Awesome that worked thanks for the fast response! now my next question... is it possible to run something like this off 3v? for a wireless keyboard?

 

Now with 3V that is a different story. Without a voltage converter to boost the supply voltage you will be limited to one LED per string.

 

8 LEDs will also very quickly drain the batteries. What you could do was to use an microcontroller and only lit one LED at any given time. If you do the switching fast enough. It want be visible to the eye. However the LEDs will lose some in brightness

 

There is no free lunch. Why not reduce the current to all LEDs in the first place?

 

MrChips is spot on with all said.
Have a look at http://www.evilmadscientist.com/2007/weekend-projects-with-bre-pettis-make-a-joule-thief/

Extra goodies to throw your way on top of MrChips' input...

The joule thief is something worth looking at.
Has a quirky cult following on the WWW with heaps of small circuits and DIY ideas.
Combine a quality LED with low power consumption transistor and you can squeeze water from a stone like this guy did...

<SNIP>

 

Hello,

A joule thief is a circuit that can raise the voltage to light a led.

In the video was something like a fraud.
No more HHO, overunity, or Meyer

Bertus

 

High brightness type LEDs can be operated at a very low current and still achieve adequate brightness as an indicator light.

 

High brightness type LEDs can be operated at a very low current and still achieve adequate brightness as an indicator light.

Yes but even so the video removed claimed that 200 LEDs in a chain made for mains voltage. Could be powered by a almost worn out 1.5 volt battery in continuous mode. They just hooked the flimsy joule thief to the mains connector. And then it was light

 

Re. the circuit you posted:
33k is a very large value for a base resistor - for 8 LEDs something like 470 ohms would be more suitable
Putting the current limiting resistor and LED on the other side of the transistor is better. At the moment it is not fully turned on so will get warmer than necessary and also there is a voltage across it so your calculation of LED current is probably messed up.

 

if your modding a laptop then you can have access to many power lines already built into the system. one of the easier ones is the 5v lines to the usb. lose a usb, gain a constant supply?

 

Hello,

A joule thief is a circuit that can raise the voltage to light a led.

In the video was something like a fraud.
No more HHO, overunity, or Meyer

Bertus

lol....I failed to mention, use the joule thief BUT don't think "FREE ENERGY"
....gawd some people.
The vid was posted to provoke thought...looks like I did that

 

wow i should have joined this forum along time ago! Thankyou everyone!

 

Generally only one thread per subject is permitted. Since there are two for this one that are well developed I would suggest any further discussions pick up over here.

Another LED pulse