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While waiting to verify the result of my Solar Charger, I starting thinking about ways to use the fully charged CR2 lithium rechargeables I had.

I came up with this 'thing', which just sits there and blinks, so I'm calling it my 'Blinkie Thingie'. Using just an inexpensive 74HC04 Hex Inverter, it provides a Color wheel or maybe a disco light for small pets.

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Step 1:

Here is a short clip of it in action:

Step 2: Circuit Design

The circuit takes advantage of the Complementary output of the 'HC' class of logic devices. It uses three low speed oscillators made from a single 74HC04 to drive six individual LEDs. This arrangement gives us a pseudo-random display, with random duration as well. There is never more than 2 LEDs on at a time, and total current drain is limited to 10mA or less.

Construction is minimal - the battery holder and the LED wheel should be finished before tackling the IC.

PARTS LIST:

IC  74HC04 Hex Inverter. Quite easy to find (RShack, eBay etc) but do not substitute!

C1, C2, C3  0.1uF (100nF, 100000pF) capacitor

R1  9.1M
R2  8.2M
R3  7.5M
R4, R5, R6  330-ohm

LEDs  x 6 Any color.

Step 3:

The CR2 is about half as long as an AA, so we could use an AA holder and trim it down. I happen to have a few 2-cell holders lying around and so I worked with that.

I started by cutting the holder in half using snips and a utility knife. The end with the wires I kept together and the other end became another CR-holder.

Leave the plastic walls on the Negative (spring) side so that the Positive end can be trimmed and slipped inside the groove. Apply plastic glue or contect cement and you're done!

Step 4:

I made a template on cardboard using a 1" (25mm) circle with six holes for the LEDs. Use the suggested layout below. Note that 3 LEDs face one direction and 3 the other.

The circled letters are LED colors if you are only using Red, Blue and Green. In general, put similar colors on opposite sides - they never light the same time. Connection points are labeled A, B and C. The points with the same letter requires a connection (dotted lines).

Step 5: The IC Chip

The circuit will be stacked free-form on the DIP body of the logic chip. Although it doesn't show it, pins 14 and 8 are for the battery + and - respectively.

Start by bending pins 2 & 13; 4 & 11 and 6 & 9 across the bottom surface of the IC so they touch each other, apply a small amout of solder to hold them together.

This type of assembly is sometimes called 'dead bug' soldering because of the legs-up form. Be careful you don't turn your IC into a real dead bug by overheating it. A good rule to follow is to keep soldering time under 3 seconds at a time, then cool the part by blowing on it for 5-10 seconds in between. It is crucial to have a good heat sink too, like the long-nose vice-grip in the pictures.

Step 6: Finishing the IC Body

Make tiny 'hooks' on pins 8, 10 and 12 to hold one lead of the capacitors C1, C2 and C3. Solder.

The other end of the capacitor should go to pins 5, 3 and 1 respectively. Make sure the wires are clear of each other.

R1, R2 and R3 is now mounted on pins 1 & 2, 3 & 4 and 5 & 6

Attach pin 14 to battery + and pin 7 to - (Ground).

Step 7: The Wheel

Attach a 330-ohm resistor to connections "A", "B" amd "C" on the wheel. Solder the other end of the resistor to pins 8, 10 and 12. It doesn't matter which order.

Trim off the extra bits, double check for wiring shorts and opens, add power and you now have a Blinkie Thingie!

In some of the videos you may see 3 lit LEDs but it is from the delayed exposure of the camera.

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