X10 Cable Build
I have an early X10 Home Control
Timer (Model CP-290) to which I have
lost the programming cable. Does
anyone know where I can get the
pinout so I could fashion my own
#3151 Leigh Guzman
In a recent thunderstorm, a
nearby lightning strike took out some
of the electronics at my neighbor’s
house. Is there anything a DIY'er like
me can build to protect my delicate
electronics — other than unplugging
everything? Something with MOVs
#3152 Matthew Hodges
PCB Chem Disposal
I’m interested in photo etching
copper-clad PCBs. Most guides don't
say what to do with the chemicals
when I'm done. Do I just pour them
down the drain or will it hurt the
environment (or my pipes?).
#3153 Gerardo Rios
My Sony BluRay/DVD player
came with a very complicated remote
control. I don't need half the buttons!
Is it possible to make a simplified
replacement remote using an Arduino
and simple buttons with an IR-LED?
#3154 Terence Rodriquez
[#2152 - February 2015]
About three years ago, I put
together a 1.5 volt battery eliminator
using a wall wart feeding into an
LM4120 regulator to power the clocks
I have around the house. The clock
that I started with is a Howard Miller
mantle clock that a company awarded
to me for busting my ass for 25 years.
After installing the eliminator, I set
the clock to the time of my crack
atomic wristwatch and let'er go. The
clock ran for almost three years with
phenomenal accuracy, matching my
watch within a few seconds but finally
died — probably from exhaustion —
having gotten no rest between battery
Well, I thought, what are you
waiting for. Get with it with the other
cheap clocks cluttering up our house;
so, I did. To my amazement, none of
the clocks running on the eliminator
could keep time anywhere near what
could be termed accurate — no matter
how much I adjusted the voltage
(usually, the clocks ran fast).
So, what gives? Why does a
battery work and my eliminator won't?
#1 I recommend looking at the
LM4120 output with a DC coupled
oscilloscope and checking for noise or
voltage drift, either short-term or long-term. I think you will see the problem.
#2 Without more information, it's
difficult to give a definite answer, but
here are three possible causes to
1. Is the output voltage correct?
Check with a DVM; anything from
1.35V to 1.6V should be okay for LCD
or quartz clocks.
2. The power supply has excessive
AC in the output, e.g., a bad capacitor.
Though you could check this with an
audio amplifier or oscilloscope, it's
easier to just put a 500 microfarad or
larger electrolytic cap across the output and see if that fixes the issue.
3. AC or RF leakage from the power
supply — either from the mains or from
a nearby radio transmitter — is making
its way into the clock. The clock circuitry is very low power, so any AC
could flip some flip-flops a few extra
times per second. To check this, you
could make a Faraday cage (e.g., window screening) around the clock and
connect it to one side of the supply.
This is to satisfy your intellectual
curiosity, though it's probably not a
convenient way to run a clock.
#3 First off, I suggest the following:
1. Measure the OPEN-CIRCUIT output of your eliminator before connecting it to the clock you want to run.
2. Connect the eliminator to the
clock, then measure the voltage output again.
If the difference between the "no-load" voltage and "load" voltage is
more than 0.5 VDC, it's entirely possible your wart isn't delivering enough
current to properly operate the regulator. In this case, try a similar-voltage
wart with higher current output (say,
1.5-2X of your current wart). This may
solve the problem as wall wart outputs
tend to droop severely once you
approach their maximum current
capability, resulting in severe output
instability (i.e., the regulator won't
"regulate" well), increased ripple, noise
on the DC output, and severely shortening the life of the wart (i.e., over-
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78 March 2015