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Solar Powered PIC

Hi all.. Sorry this is maybe a bit long winded.

I'm Just gathering thoughts together for a project that has family connection close at heart.

My father (deceased) was a lighhouse keeper on various lighhouses around Ireland and as one of those Father/Son things, I'd like to keep remembering him by having something around my home that may seem unusual to neighbours but meaningful to me plus, a conversation starter.

I used to have a lighhouse overlooking a garden pond that was powered by a simple stobe circuit but it was more of a novelty when my dad was alive.

What I would like to do now as a project is to build a PIC based project that will simulate the flashing sequence of a particular lighthouse. The PIC circuit I can get working okay via they technology department in the school I work in but what I would like to do is operate it using a solar panel so that I don't need to work with mains - everything self-contained.

I've been looking at the Garden type solar panels and notice that they only charge at 3.6V into 2 NICAD batteries at 2.8V but PIC's operate at 5V. I would like to use LED's as the light source so what way would anyone suggest I increase the charging mechanism so that I can build up a suitable voltage/current to operate a PIC circuit with LED's (say 1 bright LED)

Regards

Declan Barry

Reply to
WiseOne
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WiseOne wrote: (snip)

Lots of PIC models are speced to operate lower than 5 volts. For instance the PIC10F220 works down to 2 volts.

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Reply to
John Popelish

Standard PICs (like the 16F628) are rated to work down to 3V. The "L" (16LF628) versions can go down to 2V.

Dave :)

Reply to
David L. Jones

you could use a lower-voltage micro, (AVR's will operate from 2.7(or lower) to 5.5V). or you could double up on solar panels for twice the voltage. or use some other method eg: (a 4555 driving a 4017)

--

Bye.
   Jasen
Reply to
jasen

Most white ultra-bright LEDs (actually blue LEDs with a phosphor conversion coating) exhibit a forward voltage of more than 3 volts so you're actually better off getting your voltage to a higher level. Red LEDs exhibit about a

2 volt forward voltage drop so your garden solar circuit is probably for a red LED. I would build a voltage-doubler or tripler circuit and shoot for some higher voltage to give you the overhead needed to run the LEDs as long as possible. The downside of a higher voltage is the need for a larger current-limiting resistor but the upside is you can extract more energy from the battery, as the voltage falls, before the voltage falls below the forward voltage of the LED.

Dorian

Reply to
Dorian

You might be able to use a low voltage white LED driver chip, plenty available as free samples from e.g. Maxim IC.

For example MAX1573, 4 LED dimmable version (all leds dimmed together, not individually):

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MAX1573 is surface mount, though, and may be tricky to solder.

The other route could be to convert the NiCd pack's output into some stable higher voltage and drive the PIC and LEDs from that. MAX710-5 could work, 5V 250mA out, with at least 1.8V in. Winding the inductor isn't hard, I guess any little finger nail sized ferrite toroid (N27 material, maybe) will work with a couple of turns on it.

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- Jan

Reply to
Jan Wagner

Cheers Folks..

All have given me something to work on.

Many thanks

Declan

Reply to
WiseOne

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