■ FIGURE 6
So, if you know where I might buy
such a book, I would appreciate it.
— George Gunter USN (Ret.)
AI know nothing about this
but if the signal is not clear
voice, it may be frequency
hopping spread spectrum. I
don’t think a schematic is applicable
in this case. I found a few books at
Barnes & Noble that may be of
interest: Spread Spectrum in
Communication, ISBN-13:
9780863410345; Principles of Spread
Spectrum Communication,
ISBN-13:9780201633740; and
Crypto: How the Code Rebels Beat
the Government-Saving Privacy in the
Digital Age, ISBN-13: 9780786521951.
Another possibility is that the
signal you are trying to receive may
be digital voice. Cell phones operate
in this band and I believe most, if
not all, are now digital voice. If that
is the case, this book may be helpful:
Telecommunications and Data
Communications Handbook, ISBN-13:
9780470041413.
TOOL SETTER REVISITED
QI require a little more help
with the Tool Setter circuit
you designed for my milling
machine (May ‘08, page
25). I had to reverse the contact logic
in the milling machine so that my
30 August 2008
■ FIGURE 7
touch probe would work correctly.
Because of this change, your original
schematic for the Tool Setter will
no longer work. Do you think you
could take a second look at this
circuit for me? Here are the new
criteria for the Tool Setter:
1) The circuit is now normally closed
(NC) and must open when a tool
touches the top plate.
2) The secondary part of the circuit
needs to be isolated from the frame
of the milling machine.
3) We can still use a battery to power
the primary circuit.
4) I still would like an LED to come
on when a tool touches the top plate.
— Bill Blackburn
AThe solution is simple: just
replace the HSR312 solid-state relay with the normally
closed G3VM-353A,
Mouser part number 653-G3VM-353A.
SOLAR TRACKER
QI have three questions:
1) I am in need of a simple
solar tracker schematic.
Some years ago, T. J. Byers
sent me one that for some reason, I
can’t get to work (Figure 6). I have
changed components many times. I
wired the two pin photo transistors
both ways (no pin info); maybe you
can supply that info for me — which is
the collector, the longer lead or the
shorter one? I’ve been working with
the schematic over the years and like
it for its simplicity
but can’t seem to
make it work. What
do I do to get this
circuit to work? In
theory, it sounds
good. Could there
be an error in this
circuit? I recently
used a Darlington
transistor in place
of the 2N2222
transistor; same
results, it still
doesn’t work. What do I try next?
I won’t give up after so many years
of trying.
2) Figure 7 is an automatic solar
charger that turns on my solar lights
all around my house. While experimenting with different MOSFETs, I
find that the lights go on when it is
still reasonably light outside due to
the internal resistance of the
MOSFET. I have not tried changing
the voltage divider resistors, especially
the 1K resistor, R2. Normally, it
would be a simple task to just try
changing the value of the resistor
but unfortunately, the control box
housing for the circuit is mounted
in a difficult place. That is why
I am asking your opinion on this
particular circuit.
3) Do you have any simple solar
circuits that charge a battery during
the day then at night switch on the
outside lights? I am now using some
super bright 39 cluster LEDs which
operate on 12 volts DC.
— Antonio J. Anzevino
A1) There are no specs for
the RadioShack photo
transistor, so there is no
way to know if it should
work or not. I suspect that if you buy
enough of them, you will find a pair
that work. BTW, the shorter lead of
the photo transistor is the collector.
Instead of a photo transistor, try
using a CdS photo resistor,
RadioShack No. 276-1657. There are
five in the package so you should
find two that will work. It may work
without modification, but if you make
