Getting Somewhat More Serious 121Experiment 14: A Pulsing GlowFlying Wire Segments
The jaws of your wire cutters exert a powerful force that peaks and then is suddenly
released when they cut through wire. This force can be translated into sudden mo-
tion of the snipped wire segment. Some wires are relatively soft, and don’t pose a
risk, but harder wires can fly in unpredictable directions at high speed, and may hit
you in the eye. The leads of transistors are especially hazardous in this respect.
I think it’s a good idea to wear safety glasses when trimming wires.Finishing the Job
I always use bright illumination. This is not a luxury; it is a necessity. Buy a
cheap desk lamp if you don’t already have one. I use a daylight-spectrum fluo-
rescent desk lamp, because it helps me identify the colored bands on resistors
more reliably. Note that this type of fluorescent lamp emits quite a lot of ultra-
violet light, which is not good for the lens in your eye. Avoid looking closely
and directly at the tube in the lamp, and if you wear glasses, they will provide
additional protection.
No matter how good your close-up vision is, you need to examine each joint
with that close-up magnifier. You’ll be surprised how imperfect some of them
are. Hold the magnifier as close as possible to your eye, then pick up the thing
that you want to examine and bring it closer until it comes into focus.
Finally, you should end up with a working circuit. You can insert the wires from
your power supply into two of the tiny power sockets, and plug a red LED into
the remaining two sockets. Remember that the two center sockets are nega-
tive, and the two outer sockets are positive, because it was easier to wire the
circuit this way. You should color-code them to avoid mistakes.
So now you have a tiny circuit that pulses like a heartbeat. Or does it? If you
have difficulty making it work, retrace every connection and compare it with the
schematic. If you don’t find an error, apply power to the circuit, attach the black
lead from your meter to the negative side, and then go around the circuit with
the red lead, checking the presence of voltage. Every part of this circuit should
show at least some voltage while it’s working. If you find a dead connection,
you may have made a bad solder joint, or missed one entirely.
When you’re done, now what? Well, now you can stop being an electronics
hobbyist and become a crafts hobbyist. You can try to figure out a way to make
this thing wearable.
First you have to consider the power supply. Because of the components that I
used, we really need 9 volts to make this work well. How are you going to make
this 9-volt circuit wearable, with a bulky 9-volt battery?
I can think of three answers: