24 Hour Circuit for
I’m looking for a simple circuit for
a 24 hour electronic candle that uses
very little power. The candle would
drive a single LED. It would run for x
hours (say five), then turn off; 24 hours
after it was first activated, it would
automatically turn back on for the
I've found several ideas, but most
of them surrounded the 555 chip
which has a very limited time frame.
#11101 Scott Lapp
Simi Valley, CA
Fluke Scope and RF
I’ve had a Fluke 99B Series II
scopemeter (100 MHz) for a number
of years and it works great.
I’ve started working with amateur
radio and would like advice on using
this scope to measure RF. I think I
need an RF probe. I currently have the
set of 10:1 probes that come with the
Can the scope — using the proper
probes — be used at the actual antenna feed output from the transceiver?
#11102 Jerry Lopez
78 November 2010
I am going to build two EHT
measurement probes: one at 800 M
ohms and the other at 45 G ohms. I
will also use a 3140 op-amp or a
LM358 op-amp, but need a schematic
of the components around the op-amp
so that I can change the impedance of
the EHT measurement probe and use
it with either a multimeter or oscilloscope to check the output of the
flyback voltage and signal valves.
Russell Kincaid was kind enough
to show me how to get a 10K and 25K
sign signal out of a signal generator
and an amp to power a flyback for
my project, for a sign output from the
Also, I have a Conar Model 251
oscilloscope 1Q MHz. Can anyone
point me to a website that has the
valve of the fuse for this scope and
maybe a manual?
Part Identification and Availability
We are repairing printed circuit
boards, but cannot locate schematics.
We are looking for 32-pin microcontrollers. ID 3s are 14345 with 9122
listed below. That's it. Also, bypass
capacitors and holders, U-3A 99X.
No manufacturer logos. Have tried
obsolete part vendors. No luck. Can
Using Up Batteries
With so many devices we use
today having a power regulator in
them, our batteries become ineffective before they really run out of
power. For instance, a digital camera
will use fresh alkaline batteries for a
very short time. What can be done
with these batteries that have plenty
of life in them, but not enough to get
past the power regulator? Is it possible
to blink an LED until there is like half a
volt or less in each battery? What
interesting things can these "dead"
batteries do until they are truly dead?
#11105 Rick Montzka
[#6106 - June 2010]
I am buying my wife a car, but she
will not get the garage. So, I agreed to
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buy her a remote start. I have looked
around for one with a clock that will
start the car every weekday. So far, no
luck. I’m thinking one could program a
PIC to start the car like at 8: 30 am for
15 minutes, except Saturday and
Sunday. Of course, with an override
switch for vacations. Any ideas?
#1 I'm assuming this is only to
happen when the car is home.
The Idec Smart Relay would
be perfect; www.idec.com/usen/
SmartRelay.html IDEC offers a
software package that you can test the
logic. It has a built-in clock/calendar
with automatic daylight savings time.
The demo package can be used with
or without a relay for 15 days.
If you use the 24 VDC version,you
would have DC power available; you'll
need some DC power for the remote
interface. An OptoFET is a really
reliable interface across any remote
button. Per your suggestion — make it
start the car at 8: 30 and turn it off at
8: 45 — two outputs are needed. One
for OFF and one for ON. One input
would be used for Enable/Disable.
#2 I put an electric engine heater
on the car. That was more economical
than the gasoline to warm up the car.
Check if a block heater can be
ordered when buying a new car. Block
heaters that go in place of a frost plug
can be ordered from an auto parts
store like NAPA. There are also electric
heaters that can be connected with
A small block heater can be
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attempted by qualified individuals.
Always use common sense and good