this might sound odd coming from an electrician but i know very little about electronics. basically i have two devices i want to power, one runs on 5vDC and the other runs on 12vDC and want if possible to run them from 9v bateries. so whats the easiest way to drop the voltage going ingto each device? is it as simple as getting the right resistor and putting it across the +/- to cut it down?

Why not use a 'block' of 1.5v batteries.

12v is acheivable and the 4.5 or 6 for the 5v device.

i wonder how sensative the device is to voltage change? might be worth a shot stu

but do you connect cells in parallel or series to increase the voltage? :confused: been years since i was at college

i think its parallel but will go check

just looked, series gives added voltage

Oh bengie, I am not impressed.......................................... :nono:

I dont believe what I am reading...

Finger all you like, wont change a thing.

Finger all you like, wont change a thing.

Thats what the missus said :(

Anything I have encountered that runs off 5v needs 5v (+or- 5% of you are really lucky). If you use resistors or a potentiometer to drop 9v or 12v to 5v then as the battery runs down and the voltage drops, so will the 5v. The resistor array will also use power in itself thus running the battery down quicker. Also depending on the load the resistors may need to be quite large.

The best solution is using solid state voltage regulators. These use vary little external components, keep voltage steady regardless of the supply voltage from the battery (within limits of course) and they are much more efficient than resistors.

Try here for a 5v version. 9v is not a common voltage but it's acheivable from a 12v source using an adjustable regulator like this.

(on the finger thing).

you could just use a minature tranformer instead of using fancy voltage stabilizers

It's probably going to depend on what you want to power. If it's a steady DC load, you could probably use a resistor to drop the voltage, but you're wasting power as heat in the resistor. A voltage regulator's nicer, but they don't always give the cleanest supply. What's the load you want to power?

Phil

you could just use a minature tranformer instead of using fancy voltage stabilizers

:eek: Transformers work on the principle of electromagnetic induction. That requires an AC supply. I thought we were dealing with DC supply from batteries :confused:

:eek: Transformers work on the principle of electromagnetic induction. That requires an AC supply. I thought we were dealing with DC supply from batteries :confused:

of course you are dead right! sorry, need to put my brain in gear, twas very late last night!

i think the best way to solve this problem is with a simple voltage divider using resistors but we need to know more about the load we are trying to power with it

this might sound odd coming from an electrician but i know very little about electronics. basically i have two devices i want to power, one runs on 5vDC and the other runs on 12vDC and want if possible to run them from 9v bateries. so whats the easiest way to drop the voltage going ingto each device? is it as simple as getting the right resistor and putting it across the +/- to cut it down?

Does it need to be battery power or could you use a regulated mains supply?

i could use a mains supply but would need a chuffing long lead as i want to use it in places like the forrest of dean

i am powering a 12v camera and 5v DVR. so using that voltage regulator thingy looks good. so i just get that 59p thing and connect the loads up to he relevent outlets?? sounds too easy.

Do you want to use it near a car, or completely standalone? If the former, an inverter might be a possibility, then run the devices as if on mains...

Either of those devices is going to need fairly chunky batteries, I would guess - ordinary alkaline etc. aren't going to last 5 minutes.

the plan is to use it strapped to either a person or a bike so a car nearby isn't an option

could easily run it from one of them big square torch batteries