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78 November 2009
I am designing a project where
weight is at a premium. I need some
help designing a transformerless power
supply that can deliver 12-14 volts
at three amps. It needs to be auto
switching 110/220 VAC. I designed a
few projects in the past but they always
had a transformer. I see things like
laptop power supplies that don't have
transformers. They put out three or four
amps. How do they do it?
I’m looking for an FM circuit with
Fixed digital 95.5 MHz
Small as possible
#11092 Don Bartelson
Merritt Island, FL
Bridge Rectifier Voltage Readings
Why, when I read the open circuit
DC voltage with both sides of the
output disconnected from the rectifier,
I read the input voltage ± 10%?
However, if I reconnect the load — a 90
VDC brake — and have the output
switching device open, the measured
DC output voltage at the rectifier is
approximately 30% greater than the
disconnected output voltage.
#11093 John Coonis
Los Angeles, CA
Vehicle ECU Programming
I would like to know what kind of
programming is used in a car ECU. Is it
C, C++, Visual Basic, or something else?
DC-to-DC Step-Up Transformer
I need to locate a DC-to-DC step-up transformer that goes from 120 to
around 330 volts. It is for a DC-to-DC
converter that will drive a laser diode
and can be low wattage.
#11095 Thomas Wagner
Wireless HVAC Fan Controller
I want to install a duct fan in my
HVAC system to help regulate the
temperature of a specific room. But the
duct where the fan will go is in the attic
and the main airhandler is in the
basement. The fan runs on 120 VAC
and pulls 2A. I need an affordable
wireless system that would turn the
duct fan on and off when the main
airhandler turns on and off.
#11096 Eric Peters
Power Outage Monitor
From time to time, I experience