Pennywise solar power

An 8-volt DC solar power plant that fits on a penny.
A Clare solar cell on top of a US penny.
Pennywise because it's on a penny. Get it? Not the horror clown.

No matter whether you felt that Earth Hour was a terrific conservation tactic or an overhyped PR stunt, energy on our planet is in peril. Our daily juice (be it electric, gasoline combustion, atomic, or carbon-based), has become a precious commodity with at least one guaranteed effect: to elicit an instantaneous hot-button opinion from just about everybody.

What can you do about it? Well, one great proactive demonstration would be to stop your regular consumption of dry-cell batteries. Yes, there are numerous substitutes, ranging from rechargeable varieties to alternative energy replacements, but each of these substitutions has a debit that few of us are willing to pay. You know, “costs” like always hunting for an outlet to power a battery recharging station, or getting rid of a clean, slim-line AA battery for a gargantuan solar-driven bat-winged monstrosity.

The Clare solar cell.
The Clare solar cell on a DIP carrier. Dave Prochnow

Hidden on a page of a recent DigiKey catalog, I found a glimmer of hope for beating this battery dependency. A small SOIC-16 SMD clear IC that is capable of generating electricity when placed in sunlight or strong artificial lighting. The CPC1832 from Clare is an 8-volt solar cell that is capable of powering CMOS ICs while sitting on top of a penny (US monetary unit = one red cent).

The specifications for this diminutive wonder chip are impressive: 8VDC with a current of 50 µA. Even better, the CPC1832 has a built-in switching circuit that triggers the solar cell’s output when it is stimulated by light. Sorta like a switch that also provides power. Likewise, with such a small footprint, several cells can be joined together for increased voltage and/or current supplies, without creating a freakish Frankenstein battery replacement circuit.

The Clare solar cell, showing volts.
Clare solar cell output. Dave Prochnow

Although there are 16 pins on the CPC1832, only two are used for supplying voltage/current at its output. Pin 16 is the positive (+) output pin and the negative (-) output terminal is pin 9. While the remaining 14 pins don’t have to be soldered, establishing a connection with these unnecessary pins will help ensure a mechanically stronger solar-powered design.

Oh, your designs aren’t the SMD type. No matter. If you have a through-hole circuit design, you can still adapt the CPC1832 to your project. For example, Bellin Dynamic Systems makes a series of SOIC-to-DIP boards that can easily convert the CPC1832 to a 16-pin DIP IC platform. Even SMD soldering rookies can firmly attach a SOIC solar cell to a Bellin board.



Here are a few pointers for the inexperienced SMD worker that will help to guarantee successful professional-looking soldering:

The Clare solar cell's printed circuit board.
The Clare solar cell’s PCB. Dave Prochnow

1. Hold the solar cell SOIC package in place on the Bellin board and attach a small piece of masking tape to the chip for keeping it in contact with the board.

2. Apply a small amount of liquid flux to each pad of the Bellin board.

3. Touch the soldering iron to one of the board’s pads, not the solar cell’s pins. Carefully apply solder to the point between the soldering iron tip and the solar cell’s pin. As the solder liquefies, slide the iron’s tip towards the SOIC pin. Remove the iron and examine your solder joint. When the solder is solid, test for a strong connection, by tweaking the pin with a wooden tooth pick.

4. Solder all of the solar cell’s non-output pins (i.e., pins 1 through 8) first. When these pins are all solidly connected, remove the masking tape and solder the remaining pins (i.e., pins 9 through 16).

By adding CPC1832 8V solar cells to your next project, you will be able to hold your head high with tree-hugging pride during the next Earth Hour.