I have a small clock thing, its digital. All i want to do is add 1 or 2 LEDs so that it is lit, as its display is a small LCD type screen. It runs off two AAA batteries, 1.5V each. I am not up on electronics that much, but would it be possible to power two LEDs from this battery source aswel as the rest of the unit? I will add pic of the clock thing (really dont know how to describe it) when my friend gets up in the mornin cos he hosts stuff for me. Thanx -cLoWn
You should be able to power hte LEDs, not sure about the clock though. Do this: Take some extra wire (a CD audio cord, with one end removed works GREAT for testing LEDs.), plug the LED(s) in the end with the connector, and then wire the + and - onto the batt terminals. Then you can test them b4 you ahve to crack it open and solder, ect. I'll post a pic later if you dont get it....
I have already "cracked" it open, it is a very simple design, everything just goes into one main chip, and the LCD bit. I could easily hook up to the batteries, but they only give out 3V, wanted to knwo if 3V will enough to power say 2 3mm LEDs (blue ) for a reasonable amount of time (talking months here) and the LCD, but I think i might just have to try and see how it goes. Thanx Green Soda -cLoWn
get a couple of SMD leds and solder on a resistor.. then put them on each side of the display.. should work nicely.. If you are going to use blue leds you MIGHT be in trouble as they run at about 3.6 volts.. so they will be a bitt weak, but i think some LEDS well be ok.. (i think some work down to 3,2 volts...) but remember that the lights will stop lighting long before the clock stops working.. this is beacause the LCD uses very little power, while LEDS use a bit more...
I think your best option would be to use red or green LED's. Red LED's especially can have a forward voltage as low as 1.8V, so would last a lot longer in this application. Unfortunately I can't really seeing you getting much light out of a blue LED unless you use a charge pump from Maxim Semiconductors.
My compie has a rather large blue theme, and part of the clock is blue too (picies below, sorry bout poor quality I aint got used to mew camera yet). But there is plenty of room for me to stick in a 9V "square" battery, and then just wire up some resistors and the LEDs, would that work any better?? -cLoWn
PP3's tend to be rather expensive, and don't usually have a high capacity. If you could fit 3 AA batteries in there, and wire your LED's in parallel that should work better. I still recommend using some kind of charge pump though: http://www.maxim-ic.com/quick_view2.cfm?qv_pk=3553&ln=p
Hmm using a charge pump could be better for long term, but seems over complicated really. The 3 AAs i think could fit fine though, changing them when they run out or get low wouldnt be a problem, even getting rechargeables possibly. Thanks for all your help and advise.
Thats the plan. I was going to order just 2 3mm LEDs, but i am going to wait and do a bigger order when i have some more money, so i wont be able to have the results up for a while -cLoWn
