FAQFAQ   GalleryGallery   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in   Forum RSS Feed   Hacked Gadgets Main Site 

Lighting for keyboard

 
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> LED Projects
View previous topic :: View next topic  
Author Message
Lock-Os
HG Junior


Joined: 15 Oct 2008
Posts: 11
Location: Pittsburgh, PA

PostPosted: Wed Oct 22, 2008 8:58 pm    Post subject: Lighting for keyboard Reply with quote

I have been thinking of creating a small lighting unit from some LED's for my laptop's keyboard that I use, it's separate from the laptop, so it doesn't get any light on it. I figured it would be a good place to start.

I'm going to be using two 9V's and some blue LED's along with a capacitor to do the electronics part, I got some wood I can use as the base, so it all looks good.
_________________
Mechanic + Engineer = Mechaneer
Back to top
View user's profile Send private message Send e-mail AIM Address

Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Thu Oct 23, 2008 8:43 am    Post subject: Re: Lighting for keyboard Reply with quote

Lock-Os wrote:
I have been thinking of creating a small lighting unit from some LED's for my laptop's keyboard that I use, it's separate from the laptop, so it doesn't get any light on it. I figured it would be a good place to start.

I'm going to be using two 9V's and some blue LED's along with a capacitor to do the electronics part, I got some wood I can use as the base, so it all looks good.


Sounds like a fun project. There should be no need for a capacitor, but you will need a current limiting resistor.

We can help you out with LED. Smile
http://alan-parekh.vstore.ca/index.php/cPath/4_6

You can also look into pulling the power from the keyboard power. There is usually 5 volts there and it should be able to handle 20 or 30 mA.
Back to top
View user's profile Send private message Send e-mail
Lock-Os
HG Junior


Joined: 15 Oct 2008
Posts: 11
Location: Pittsburgh, PA

PostPosted: Thu Oct 23, 2008 2:52 pm    Post subject: Reply with quote

Oh... I meant to say resistor. Oddly enough, I was using a resistor to start out with but it seemingly turned out that I didn't need one.

I also ran into some odd problems in that I ended up using 3 9V cells to power 3 5V blue LED's without a resistor. I'm worried that I'm going to blow out the bulbs early if I do that, but yet it doesn't seem like anything happens if I don't have the resistor in there. Are blue LED's more 'accepting' in their range of amps compared to, say, a green LED?

Also, while I was using 2 9V cells to power the 3 5V LED's, they were significantly underpowered and not giving off any light. Therefore: 2 x 9= 18 volts, and 3 x 5 = 15 volts. so that leaves a 'surplus' of 3 volts. That seems plenty enough to overcome any resistance in the system.

I'm not sure about it, but it might be because I was using screws and nuts to hold the wires into place while testing the whole set up and incurring some loss there when the current goes though the steel screw. The more likely other reason is that I've noticed that some of the wires I've used apparently don't use copper cores. I don't think it was silver, as it was from an old electronics lab I had as a kid, so lead comes to mind.
_________________
Mechanic + Engineer = Mechaneer
Back to top
View user's profile Send private message Send e-mail AIM Address
Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Fri Oct 24, 2008 12:27 am    Post subject: Reply with quote

Lock-Os wrote:
Oh... I meant to say resistor. Oddly enough, I was using a resistor to start out with but it seemingly turned out that I didn't need one.

I also ran into some odd problems in that I ended up using 3 9V cells to power 3 5V blue LED's without a resistor. I'm worried that I'm going to blow out the bulbs early if I do that, but yet it doesn't seem like anything happens if I don't have the resistor in there. Are blue LED's more 'accepting' in their range of amps compared to, say, a green LED?

Also, while I was using 2 9V cells to power the 3 5V LED's, they were significantly underpowered and not giving off any light. Therefore: 2 x 9= 18 volts, and 3 x 5 = 15 volts. so that leaves a 'surplus' of 3 volts. That seems plenty enough to overcome any resistance in the system.

I'm not sure about it, but it might be because I was using screws and nuts to hold the wires into place while testing the whole set up and incurring some loss there when the current goes though the steel screw. The more likely other reason is that I've noticed that some of the wires I've used apparently don't use copper cores. I don't think it was silver, as it was from an old electronics lab I had as a kid, so lead comes to mind.


You should stick a meter in the circuit to see if you are giving it too much current. I would always suggest using a current limiting resistor since unlike a light bulb a LED will not accept a wide range in voltage.

With the low voltage it did not turn on since an LED is a diode as the name implies (Light Emitting Diode). A diode has a forward turn on voltage that must be reached for the device to start conducting. Again this is very different compared to a bulb that will work dimmly at 1/2 or 1/4 of it's rated voltage.

I am not sure what the 2*9 math is about? Could you clarify please.

The wire is most likely copper but it may be tinned, scrape some of the wire with a utility knife to see if there is copper inside. Lead was never used as a conductor since it is too easy to break. Aluminum was used quite a but but usually for larger gauge wire.

Hope this clears a few things up. Smile
Back to top
View user's profile Send private message Send e-mail
Lock-Os
HG Junior


Joined: 15 Oct 2008
Posts: 11
Location: Pittsburgh, PA

PostPosted: Fri Oct 24, 2008 1:33 am    Post subject: Reply with quote

Well, regarding the math, I was trying to figure out the minimum power needed to run the system. 3 5volt LED's should drain 15 total volts from the system. Now, I had 2 9volt batteries powering that system giving a total 18 volts supply, but it seemed that the LED's were very week.

I was wondering what was going on since the I was giving more power than what they needed, but they were barely lighting up. Now the math said I had a 3 volt surplus, from taking the (volts supplied) - (volts used), hence: (2 * 9Volts) - (3 * 5volts) = 3volts left over.

I guess the real question I had in mind is what is a normal drop in voltage in a simple, small circuit? 3 volts seems a bit much for me, but I'm starting so I really don't know what's normal.
_________________
Mechanic + Engineer = Mechaneer
Back to top
View user's profile Send private message Send e-mail AIM Address
Tekwiz
HG Contributor


Joined: 20 Oct 2008
Posts: 36
Location: Vancouver Island

PostPosted: Fri Oct 24, 2008 1:50 pm    Post subject: Reply with quote

9 volt batteries, have fairly high internal resistances, & this is likely what is limiting your LED current & producing a lower voltage reading. A good thing, too, otherwise you would have fried your LEDs. With a decent current source, 1/2 volt is enough to go from barely lit to totally fried.
Back to top
View user's profile Send private message
Lock-Os
HG Junior


Joined: 15 Oct 2008
Posts: 11
Location: Pittsburgh, PA

PostPosted: Fri Oct 24, 2008 4:53 pm    Post subject: Reply with quote

Thanks guys for the help, I really appreciate it all.
_________________
Mechanic + Engineer = Mechaneer
Back to top
View user's profile Send private message Send e-mail AIM Address
Display posts from previous:   
Post new topic   Reply to topic    Hacked Gadgets Forum Index -> LED Projects All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



Powered by phpBB © 2001, 2005 phpBB Group