Author Topic: Voltage regulator (Read 2214 times)

wildbill hickup · « **on:** February 08, 2005, 03:48:40 PM »

I have a 12v LED circuit that I have made for lighting. The system is feed by a 12 battery charged by a wind genny. I don't have to worry about overcharging the bat at this point, but I have found out that the LED's are pretty picky about overvoltage. In the past I have had the LED's fry when I get high wind.

I have a bunch of computer power suppies laying around and I thought it might be possable to regulate the output voltage to the LEDs using the DC side of the power supply. In otherwords say 12 to 15 or 20 vdc in and a regulated 12vdc out.

Right now I just have the output to the LEDs (with resistor wired in series) wired in parallel to the input from the jenny. Ocassionally I have LED's burn out from what I believe are momentary surges of relitivly high voltate from the genny (15+) can I use the 12v regulator circuit in the power supply to control this?

I have done some searching and can't come up with exactly what I'm looking for, maybe it's not possible, or I'm not typeing it in right. If possible can anyone point me in the right direction

ghurd · « **Reply #1 on:** February 08, 2005, 09:31:38 AM »

A LM7812? But it 'may' need 13v to operate. Some put out what they can, not exceeding 12v, but have a voltage drop.

Or a LM7810, But it would need changing the resistor (to a lower value) to the LEDs to get full brightness.

G-

iFred · « **Reply #2 on:** February 08, 2005, 09:35:56 AM »

Hi Bill.

it is suggested to to hook LED's in parrelle as you have. Here is some importent links that have some good info on the subject. They also have calculators for LED's and resistors. As for the computer power supply, They are 110VAC input and +12,-12,+5,-5,+2.5 or so voltages..

You could use a couple simple LM7812 12vdc+ voltage regulators( each is good for one amp) and can be hooked up in parelle to increase the amps to whatever you need. any standard peice of metal or heatsink can also be used. Good Luck!

Fred.

Basics of LED's - calcs

http://wolfstone.halloweenhost.com/TechBase/litlpo_PoweringLEDs.html

Everything on LED's

http://wolfstone.halloweenhost.com/TechBase/litled_LightEmittingDiodes.html

iFred · « **Reply #3 on:** February 08, 2005, 09:37:58 AM »

oppps. made spellinmg error, damn keyboard or dislexia..

It is suggested to "NOT" hook up LED's in parelle!

Barnac · « **Reply #4 on:** February 08, 2005, 09:38:58 AM »

Hy Wildbill,

Have a look at this:

http://www.otherpower.com/otherpower_lighting_leds.html

It could help.

Regards

Barnac

Flux · « **Reply #5 on:** February 08, 2005, 10:44:40 AM »

Led's are best current driven. If you are going to use a regulator it would be better to regulate at constant current, then you can let the volts go where it wants.

Flux

geoffd · « **Reply #6 on:** February 08, 2005, 02:29:44 PM »

Hi

You could place a Zener Diode around the LED's. If you made it a 12 Volt Zener it would protect your LED's by conducting the excess 3 volts.

IE

Plus 12 Volt ---< Resistor >------+------<LED>----<LED>--- etc ----+----- Minus | | .-----------------|<----------------------. 12 volt Zener.

The Zener would need to carry the voltage drop * the current. E.g. 12 volt * 50mA = 0.6 Watt so in this case you would need a 1 watt or more 12 volt Zener.

Cheers

Geoff

P.S. It took me ages to get the diagram to come out right, I hope it is ok on everyone else's browser!

tecker · « **Reply #7 on:** February 08, 2005, 06:30:59 PM »

Batteries

nothing to lose · « **Reply #8 on:** February 09, 2005, 10:15:16 AM »

Thanks from me too for the led links, I will be looking them over myself.

That rock house I mention at times that I rented has a dark stairway fairly steep I worry about someone falling down at night if the power is off (dead batts.) so I figure on using leds as baseboard lighting all the way down the stairway. 1 or 2 leds per step. Should look cool too as much as being safer. Might put it on a light sensor so they are always on at night and off during the day then run them off a 7 amphr UPS type battery. Should last a few days without rechargeing if needed.

Nando · « **Reply #9 on:** February 09, 2005, 07:44:05 PM »

Wildbill Hickup:

LEDs do not use voltage, they use current, so your circuit should be a constant current source.

With enough dynamic range to cover the voltage required for the number of LEDs in series.

The power supplies found in the PC operates on the high voltage side, some of then need 300 volts to operate ( 100 to 230 volts AC).

You can not use the PC supplies for the idea you have in mind.

Regards

Nando

wildbill hickup · « **Reply #10 on:** February 10, 2005, 03:59:33 AM »

Thanks guys for all the info. I had the PS's layin around so I was hopin I could use them, but the 7812 regulator sounds a whole lot easier and quicker. Thanks again.

WIldbill

wildbill hickup · « **Reply #11 on:** February 10, 2005, 04:24:39 AM »

That is exactly what I have done. Dark stairs, always left a 15 watt CFL on as night light. Now I have 6 10000mcd LED's, one on every other step, plan on adding 2 more in tea candle sconces, one at the top one at the bottom. Also plan on adding probably 6 or 8 more in the basement( on stairs, over wood pile, over battery location, etc). They give off plenty of light for nightlight use and the six I have on the stairs are only using a fraction of the 15 watts. The CFL is fine (and probably more efficient) if you want more light, but I don't want to read a book while going down the stairs, I just want to find the stairs! :->

ghurd · « **Reply #12 on:** February 10, 2005, 08:13:29 AM »

A 7ah battery could last for a month with a good design.

G-

Fieldlines.com: The Otherpower discussion board

News: