www.nutsvolts.com/index.php?/magazine/article/september2011_QA
MAILBAG
another option.
Dear Russell: Re: Power from
Spring Runoff, June ‘ 11, page 22.
In your June Q&A, you gave an
answer in “Power From Spring
Runoff” on how to obtain electrical
power from a mountain spring. For
the 10 foot “head” you specified, it
will take a flow of approximately 530
gallons per minute to get 1 KW,
assuming an alternator of 90 percent
efficiency. I don’t think I have ever
seen a spring produce this much
flow. Power in a hydraulic generator
system is a function of the pressure
drop between the generator turbine
inlet and discharge, and the
volumetric flow rate through the
turbine. In this case, the pressure
drop is a 10 foot head of water
(around 4. 31 pounds per square
inch) since the top of the spring and
turbine discharge are both at
atmospheric pressure. It takes a lot
of water and/or a lot of pressure
(head) to generate electricity. This is
a fact not really understood by most
of the alternative energy crowd.
— Tim Brown PhD, PE
Dear Russell: Re: USB Battery
Charger, June ‘ 11, page 24.
Response: Yes, my fault. I had
two Figure 3s and only submitted
one. The missing graphic is
Figure A; it is a picture of the USB
connector.
Re: Video Amp, May 2011, page 26.
Response: Toby Norton built the
video amp and reports that it works
great. He sent a photo of the
finished circuit and power supply
which is shown in Figure B. Figure C
is the schematic of the plus and
minus 5V power supply. Thanks for
the feedback, Toby.
■ FIGURE A
Response: Thanks for the
feedback, Tim. I had no idea how
much power could be developed.
Dear Russell: Re: Wireless
Control, June ‘ 11, page 25.
I’ve used X- 10 modules for
years; a Powerhouse RR501 RF
transceiver converts the RF from any
of their ‘pocket’ remotes to X- 10 in
conjunction with a contact module
UM506. The module output can be
wired across the open contacts of
the garage door opener. It costs less
than $50, even if you don’t have any
X- 10 stuff already! I was also able to
have the receiver in my car learn the
pocket remote.
Dear Russell: Re: Unknown IC,
June ‘ 11, page 24.
While the SAD1024 is an
obsolete (and very hard to find, if at
all) chip, there are other BBDs
(Bucket Brigade Devices) such as the
MN3010 or the MN3007. The MN3010
is a dual 512 BBD — similar to the
SAD1024 — while the MN3007 is a
single 1024 BBD.
MCMelectronics.com has
the MN3007 in stock
while DigiKey.com
lists both the MN3007
and the MN3010 for
RFQ.
As for the TL057, is
it possible that the
designer meant to use
a TL051 or TL052?
Poorly written or bad
copy can make a one
or two look like a
seven. Can’t tell
without the schematic.
— Charles Ryberg
■ FIGURE B
— Dennis Jones
Response: Thanks for the
feedback, Dennis. This is
■ FIGURE C
indicate the signal level. When R5 is
at ground (zero ohms), the maximum
amplitude is 1.25 volts peak and
when R5 is at maximum, the peak
amplitude is 2. 5 volts. The input
circuit is a high-pass filter with a
zener diode to protect the amplifier
from spikes. I used 600 ohm
impedance even though the line
impedance may be less because the
filter response is okay and the
attenuation is less.
24 September 2011
1.5V HOBBY MOTOR
SPEED CONTROLLER
QI am trying to control the speed of a 1.5 volt hobby motor. I have come up with the circuit of Figure 6. This
speed controller works. However, I
do not know how efficient it is or if
my circuit is correct.
I used a basic circuit I found in
one of my Forrest M. Mims III
Engineer’s Mini-Notebooks and
worked from there. I achieved
my resistor and capacitor values,
mostly by hit or miss or trial and
error.
