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78 June 2009
DC Motor and Inverters
Can I run a permanent magnet
90 VDC motor on a 1,500W inverter?
I need to reverse the motor and was
going to run the inverter output
through a full wave rectifier. The motor
draws about eight amps.
Three Volt LED Solar/Charger
Most, if not all, outdoor pedestal
lights are 1.5 volts with a very weak
LED. With the advent of super bright
> 10,000 mcd white LEDs, we need a
circuit we can drop in (after gutting the
old one) that will give a meaningful
light source. I entertained a Maxim
DC-DC step-up but the existing circuits
are current limited. So, how about a 3.x
solar source, photocell, a pair of 1.5
VDC batteries, and the charger circuit
with photocell switch?
#6092 Ron Spatafora
Autoranging Digital Panel Meter
Does anyone know of a self-contained, autoranging digital panel
meter? There are lots of fixed, 200 mV
range, self-contained digital panel
meters that simply require a power
supply and appropriate voltage divider
to measure a fixed range of input
voltages. I would like to measure from
1m VDC to 400 VDC with three or four
digit accuracy. Or, is there a way to
make a self-scaling, autoranging voltage
dividing, input circuit that would then
utilize a standard self-contained panel
meter to accomplish the same task?
There are many good quality DMMs
that are fully autoranging, but they
are very difficult to disassemble and
implement into a stand-alone system.
Most have auto-power-off circuits
and other features that make them too
cumbersome to implement.
Monitor Home UPS
I would like to be able to use an
oscilloscope PC application to monitor
the 120/240 output of my UPS. I found
a couple of applications that utilize the
PC's sound input.
Can the 240V output be effectively
and safely reduced to the voltage level
of the PC mike input?
#6094 Curt Timmerman
Triac Controlled Light Switch
I’m looking for a circuit to run a
low wattage 120 volt incandescent
light. The source will be a Parallax
BASIC Stamp II microcontroller (5V @
30 mA per I/O) and the circuit needs to
be opti isolated. I’d like to use a triac
if possible. The light will be off for
short periods of time (two to five