Electronics question

[Kwacker]

I have no power in my garage.

So I bought a pair of those really cheap led lamps that you push to switch on (these came with a remote control as well). They run on 4 AA batteries, however they don't last very long.

I also have in the garage an old 12v motorcycle battery that I can connect to a solar charger to keep it topped up.

My question is how do I connect the cheap led lamps up to the motorcycle battery without melting them or causing a fire?

I tried to work it out myself but I suppose that after 20years whatever I had learned in my electronic engineering class is simply gone!

If you can help please keep it simple I am handy with a soldering iron but that is about it!

thanks

Kwacker

[Simpo Two]

4x AA batteries is about 6 volts, so we presume your LED lamps require 6V to work. How about two lamps in parallel, thus splitting the 12V?

Or is it series? One or the other, anyway.

Please note this is just a wild guess.

[OldSkoolRS]

To achieve the required 6 volts across each LED lamp would require them to be connected in series (ie one after the other). This way you will effectively 'split' the 12 volts in half. Be aware that car batteries can often go above 12 volts (especially when a charger is connected), but hopefully the smaller over voltage will be OK (plus it will also be divided in two, so 12.6 volts would give 6.3 volts to each LED lamp).

Hope that makes sense....but it is Friday and it's been a long week.

[spikeyhead]

In series

[Deva Link]

It's series for 2 x 6V items, but whether they are 6V or not rather depends on how the lamps are wired intermally - the 4 AA batteries could be connected in 2's, so 2 sets of 2 in parallel therefore the voltage going to the lamp would only be 3V.

Hopefully the battery compartment will be quite crude and you can see the wires going into the lamp from either end of the series of batteries. In this case it would be 6V and you could just solder (or attach some other way) some wires so you've got the two battery compartments connected in series.

You need to go from the +Ve of the car battery ideally through an inline fuse (a bullet one as used in car accessories would be OK) to the +ve terminal on the first lamp then from the -ve terminal of the first lamp to the +ve terminal of the second. The from the -ve terminal on the second lamp to -ve of the car battery.

[annodomini2]

http://www.instructables.com/id/Fast-Quick-Cheap-G...

[Simpo Two]

Series. Righto, I knew it was definitely one or the other!

Deva Link said:

It's series for 2 x 6V items, but whether they are 6V or not rather depends on how the lamps are wired intermally - the 4 AA batteries could be connected in 2's, so 2 sets of 2 in parallel therefore the voltage going to the lamp would only be 3V.

It might say the voltage on the lamp somewhere.



Zener diodes anyone?

Edited by Simpo Two on Friday 10th July 18:48

[OldSkoolRS]

Simpo Two said:

Zener diodes anyone?

Edited by Simpo Two on Friday 10th July 18:48

The current would be too high to use zener diodes directly, so you end up building part of a regulated power supply by adding power transistors in a common emmiter arrangment.

We used to have some ancient Germanium diodes where I used to work, which is going back some (we used to repair valve amps too ).

[Deva Link]

Simpo Two said:

It might say the voltage on the lamp somewhere.

It's not really lamp (as in a bulb) it's an LED. I used the term lamp to refer to the whole unit.

[Zad]

Or just buy a couple of cheap 12v fluorescent tube lamps that they use on caravans?

[Kwacker]

I would just buy some 12v lamps but these have remote controls. I've got one in the car and one on the garage door for convenience.

Kwacker