■ WITH RUSSELL KINCAID
In this column, I answer questions about all
aspects of electronics, including computer hardware,
software, circuits, electronic theory, troubleshooting,
and anything else of interest to the hobbyist. Feel
free to participate with your questions, comments,
or suggestions. Send all questions and comments to:
Join us as we delve into the
basics of electronics as applied
to every day problems, like:
Flickering Lamp Circuit ✓
● USB Tester
FLICKERING LAMP CIRCUIT
QI use several oil lanterns that I modified and wired to use 12 volt low voltage landscape sockets and lamps running off a transformer for my Halloween
display. I would like to get the bulb to flicker like a flame to
be more natural. Is this possible and can I do it cheaply?
— Bill Bartsch
AIn December ‘05, the late T.J. Byers published a neat circuit for an LED; I have modified it with a power transistor to drive a lamp (see Figure 1). The transistor
is rated at 1/2 amps and may need a heatsink. You can tweak
the values to get the effect that you like. The four oscillators
are running at different frequencies and are not synchronized,
so there is a variation in the light intensity. If your lamp
requires more than 500 mA, a TIP41 transistor will work but
you will need to tweak the resistors 5-8 for the best effect.
FM RADIO PROBLEM
QI purchased and built an FM radio in kit form from one of your advertisers (
RamseyElectronics.com) and, although it works just fine, I encounter a problem
when I increase the volume. It ‘skips’ to the next station. Can
you please point out where the problem may be? I’m using a
12 VDC 100 mA power adapter for it, instead of 9 VDC
as indicated on the schematic that came with the kit.
— Michael Williams
AI have reproduced the suspect part of the circuit in Figure 2. The DC from the discriminator is fed back to the tuning diode to hold the station on frequency.
If the coupling capacitor, C9, is leaking or in backwards,
changing the volume will drag the DC voltage
down and cause the frequency to change.
Check C9 and if it is not backwards, replace
it with a tantalum 10 µF, 16V. The circuit
should work okay on 12 volts.
■ FIGURE 1.
■ FIGURE 2.
WATER SOFTENER QUESTION
QI recently received an ad for an “electronic water softener.” It appears to consist of a coil around a copper pipe with a
controller attached. My questions are: Does this
have a scientific basis? Wouldn’t the copper pipe
shield the water from magnetic and electrostatic
fields? Do you know of anyone that has used one?
— Kenneth Keck
AI have never heard of electronic water softening. You are correct; the copper pipe will shield the water from AC
fields. I am sure the ad did not explain how it
works because it doesn’t. I found out that this
device is marketed by Eden Pure — the
company that markets the electric heater