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Subject: Re: simple DC light design

Date: 06/14/01 at 9:33 AM
Posted by: Andre Laurent
E-mail: andre.laurent@alltec.com
Message Posted:

In Reply to: Re: simple DC light design posted by Ray on 03/18/01 at 11:38 AM:

Bulbs****************
Bulbs in series, if one of your bubs decreases in resistance, there is the uneven lighting effect & higher drain.
However, you can not run bulbs at anything other than the voltage specified. That is the surest life shortener there is.
BUT!!! There is no really good reason to choose one or the other if you use the right voltage. For parallel implementation, short of including a current
monitoring circuit for each bulb & then using a switching algorithm in an intelligent device to maintain balanced current, it only gets too complex.

Photocell***********
I am no expert, but 15% efficiency is what you will get with basic silicon cells (if you are lucky) Cheap surplus stuff is another matter all together.
With GAs cells you can get 25%, but you would have to sell your soul for those. MAXIM, Dallas (now owns MAXIM) or linear tech probably have battery charge
devices on a chip that can be configured to work with solar cells. I would experiment with cells from a surplus store first. Building a peak power tracker
for this will get expensive, but is not too difficult.

Dusk turn on, 4-5 hour burn time******
Use a photodetector, op-amp & a simple 555 timer. Reliable, cheap & easy. TO get really fancy use a pic or Atmel device (8pin).
since you are asking for approx 4-5 hours, accuracy is not an issue.

Batteries**************
I agree with the preceding comments, the battery choice is simply one of power draw & burn time required. Amp-hours.
You figure out how many amps for how many hours, at the voltage you are running & choose the cells. This will also impact the solar cell size as
you will need to replenish the battery charge with available solar power.

Funny, that you can implement the same idea with a 10,000 mcd lcd cluster, reflector/diffuser & some AA NiMh batteries!!!!

I f any further assistance is required, you have contact co-ordinates.

Disclaimer: This advise is not warrentied to be of use to anyone, anytime, for
anything. In other words the "inclusive or" of all Warrenty exceptions given by
software manufactures.


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