Batteries

steam235 · Post by **steam235** » Thu Nov 15, 2012 1:30 pm

Ok I may be in trouble i've built my refit all based around it being powered by three batteries in series. So three C cells or D cells. Providing 4.5 volts.

However I am now using about 80 LEDs each draws about 20 Ma.

Does the resistor add to how much power the led draws?

If not my ship draws about 1400 Ma. Which is 1.4 amps?

Can three c cells or even d cells produce that much current?

Max Nex · Post by **Max Nex** » Fri Nov 16, 2012 10:03 am

ma stands for micro-amperes -1/1000th of an amp
1.4 Amps would fry all the l.e.d.s and the wiring unless it were pretty big.

steam235 · Post by **steam235** » Fri Nov 16, 2012 10:44 am

My circuit uses about 80 LEDs each at 20ma 80*20=1400 so wouldn't all 80 draw around 1.4 amps in total?

Joseph Osborn · Post by **Joseph Osborn** » Fri Nov 16, 2012 11:51 am

A milliamp is one-thousandth of an amp. 1400 milliamps equals 1.4 amps. The power requirements of your LED array is determined by the way they are connected to the power source, i.e. series or parallel. Your three C or D cells can power that many LEDs but you can't just string them up in series and expect it to work. And yes, the resistors absorb a little bit of current and turn it into heat. You should probably play around with one of the online LED resistor calculators and try to come up with an optimal way to group your LEDs into parallel subsystems of about four or five LEDs each. I've never put more than seven or eight LEDs into a single model, so I don't have any practical experience with a project as big as your Refit!! This is one of the reasons why there are so many aftermarket lighting kits for the Refit ~~

Go4Fun · Post by **Go4Fun** » Fri Nov 16, 2012 11:22 pm

If it isn't on the instruction sheet I would not know how to do this.

"Don't worry Marie, they're only free electrons"! Young Einstein

starsend · Post by **starsend** » Tue Nov 20, 2012 7:57 am

I assume you resistored your LEDs based on a voltage of 4.5V then? If that is the case, just buy a 4.5v power supply that exceeds 1.4 amps. You can probably find one that goes from 3V to 12V and just select 4.5. I you can't do that you could buy a voltage regulator and use a 9V/1.5 A power supply. The regulator will bring the voltage down to 4.5V and you'd be all set.