A different saber use, help needed

[koolerking]

Hi

This may be a strange requests. I've registered here for some help on a project in undertaking, and the saber making is the closest thing i can find to help me.

Im making a LED mic stand and ive got the ideas for most of the parts needed but i need help on the electronics, and you guys will know best!

Ok, so im looking for a blue LED, i think ive come up with the Blue P4 as it uses a low voltage of approx 3.4 volts. I need to not have to many batteries (2 AA) and long run time, approx 4 or more hrs. I was looking at the 3.7 volt AA thrusted type in a parrael configuration that could get a high run time with a P4.

I worked out that these buck pucks will help on the run time but i noticed that they need a 5v minimum input, so im a bit confused how i would you the lower voltage of the P4?

I would like to also charge the batteries (li ion type) from an external charger, would i be able to wire this to the AA battery holder? I've also noticed there is a protection circuit you need for charging li ion batteries, how do you wire that up?


Lots of questions, id be really grateful if anyone has some info. :o

Thanks

[Lord Dottore Matto]

Okay, it is as easy as this: (1) 18650 Li-ion. (1) 3.7V PCB. (1) Seoul P4 (1) 2.1mm recharge port (1) 1 Ohm 2 Watt resistor or (1) 1A buckpuck. (1) latching switch (any type you like)...Add some heatshrink and a charger and you have it. 4 hour run time...well, 3 at least or you could run (2) 18650's in parallel for amazingly long run times. The diagrams to wire this up are all posted on this very forum, so with a little elbow grease you can have this project finished in 1 hour.

[koolerking]

Brilliant, thanks for that. I was thinking of doing the parrallel 3.7 v batteries to get the run time up.

thanks again

[Enolmano]

And this is how you calculate the exact (theoretical, that is. So exact-ish)

Take the number of mA hours (like 6600mAh) your battery has. If you use multiple cells (witch you will...^^) just add them up. IE 2200mAh + 2200mAh + 2200mAh = 6600mAh
Divide by the how much current your LED (like 1000mA)

Total milliamp hours / what your LED is sucking = runtime

6600mAh / 1000mA = 6,6 hours

You said in your first post that you were looking for a runtime about 4 hours.
If your LED wants 1000mA you'll need a total of 4000mAh. Theoretically.
IRL I would say more like 5000mAh.

EDIT: I will need too see pics of that microstand later on! :D

[Novastar]

If a circuit is running/controlling the current to the LED, you will get varied results. For example, a PWM (pulse width modulation) circuit that is outputting "1000mA" is not actually 1000mA. It will be a range of current, depending on the way the circuit is built.

In general, PWM circuits utilize the battery energy more efficiently... although of course a circuit also takes voltage and current to run too.

So... it's almost never a cut & dry thing, although yup... the "mAh" rating is a decent enough estimate.