in detail, it may be possible to write a
program to accomplish the desired
result. From your questions, I sense
that you do not know how this circuit
works and I cannot help you with that.
QI have only received a couple issues of Nuts & Volts and enjoy your Q & A section. Therefore, I
Dear Russell: Re: Leak Noise
Correlator, July ‘ 11, page 22:
With regards to Howard
Epstein’s question regarding a “Leak
Noise Correlator,” you might want to
check your definition of velocity (V).
Using V = D/T, the quantity T1 + T2
becomes D1/V + D2/V, and that
becomes the constant K = (D1 +
D2)/V or D/V, the known quantity.
∆T = T1 - T2 = D1/V - D2/V
= D1/V - D2/V + D2/V - D2/V;
cleverly add zero then regroup the
= D1/V + D2/V - 2D2/V
= K - 2D2/V
In a similar fashion as above, by
adding zero in the form of (D1/V -
D1/V), we get:
= 2D1/V - K
Simple algebra gives the two
D1 = (K - ∆T)V/2 and D2 = (K +
— Ken Meier
24 November 2011
Response: Thanks for the
■ FIGURE 4.
thought you might be able to help
me with a simple circuit I need to
Here is my situation: I have two
solar panels on the roof of my van
camper to keep the batteries
charged. A problem developed in the
ignition switch that put 4 ohms to
ground on the + side of the batteries.
Since I wasn’t using the van, I
didn’t notice the batteries going
down. Eventually, what apparently
feedback, Ken. If I had plugged some
numbers in, I would have discovered
my error in the beginning! I wonder
how many were aware that I started
off with the wrong premise? You
were the only one to let me know of
the error and I appreciate the
opportunity to let the readers know
that the math was wrong.
Dear Russell: Re: Transistor
Replacement Needed, August ‘ 11,
I love your column but found a
major error in the theory of
operation for “Transistor
The International Rectifier B2M
was a popular circa 1966 hobbyist
photovoltaic (solar) cell and not a
photoresistor. The germanium
transistor is merely used as a
“common emitter,” albeit one
requiring a lower base voltage than
a silicon transistor to turn it on.
R1 and C1 are simply a snubber
to protect the transistor from back
EMF transients when the coil is de-energized.
Workarounds to allow a silicon
happened was the batteries became
so low they drew more current than
the controller could handle.
The solar panels are putting out
19V but, the controller was putting
0V into the batteries. The controller is
a SOLAR COMMANDER SERIES IV
model FM16C made by Kyocera
Solar, Inc., Kyoto, Japan which they
no longer manufacture or repair.
This controller is quite
complicated with five LEDs, a screen
that shows voltage, and a pushbutton
to show amps. I don’t believe I need
such a sophisticated device.
Back when I was working in
electronics — almost 50 years ago —
we used tubes, not these tiny little
components the size of a grain of
rice that I have no idea what they
What say you? Am I a hopeless
case or could you develop a
controller that would suffice for my
application? I wish to keep two 12V
vehicle batteries charged. I can still
read a schematic, more or less.
— Denis Kellogg
AI checked the Harbor Freight website; it has a 15 watt solar panel. Two of them would be more than
transistor to be used include using a
second B2M in series to provide a
higher drive voltage, or returning
the grounded end of the original cell
instead to the tap of a voltage
divider between B+ and ground so
that the cell voltage adds to the tap
voltage. The drawback would be a
constant low current drain on the
battery due to the divider.
Better yet would be to replace
the B2M as well, by using a
common phototransistor along with
a suitable current limiting transistor
between base and B+, with a second
resistor between base and ground to
ensure that the transistor remains
off when the light level is below the
desired turn-on threshold.
Relays with ultra-sensitive
4,000Ω coils (~ 20 mW) are also quite
expensive and difficult to find. There’s
no reason other than battery life
why a far more economical normal
sensitivity relay couldn’t be used.
— Don Eden
Response: Thanks for the
feedback, Don. I was on the wrong
track on that one.