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18v AC to DC Power Supply
This is a classic linear power supply which produces a regulated 18v,
rated at about 1 amp. (added 7/06)
240VAC To 5VDC Power Supply
This is simple way to power some 5v logic from a 240vac source. If a
120vac power adapter is used, the circuit will also work for 120vac power
lines
24VAC Powered Isolated +5v Supply
24vac is a very popular power supply in many industrial systems. It is
often used in systems that involve water. It is also popular with many
inside and outside lighting systems. The lower voltage means the danger of
human electrocution is much less. But, many DC powered sensors and control
circuits associated with 24vac systems need to be fully isolated from the 24vac
supply. The circuit below accomplishes this feat
Caps Provide Voltage Boost To Series Regulator
This circuit adds some capacitors and diodes to a traditional transformer type
series regulator circuit to extend the normal operating range. It can insure
regulation during low line voltage conditions or it can squeeze a few more watts
out of a plug-in-the-wall power adapter power supply.
Classic Plus &
Minus DC Power Supply
This is a classic example of a regulated DC power supply that produces both a
positive 15v and a negative 15v from a 20vac wall adapter.
Energy Harvesting Using a Current Transformer
Energy harvesting is all the rage these days. With some modern
electronics, information from low power sensors can be sent to a distant data
collection point using a low power RF transmitter. To power these remote
sensors, various energy sources can be tapped into. Machine vibration,
temperature differences, ambient light and stray RF have all been used as low
power energy sources. Sometimes, the sensors are located near AC power
cables. Rather than making a direct connection to those cables, an AC current
transformer, such as the one shown below, can be used to capture a bit of power
Low Power 12,000 Volt Power Supply
If you need about 12,000 volts DC for an ion generator this circuit might be the
ticket. It draws power from the 120vac power line but it uses a small 6KV camera
flash trigger coil. The output signal is isolated from the power line. Although
the circuit can only deliver about 5uA of current it can produce dangerous
shocks, so be careful
Miniature Isolated AC/DC Power Supply
This circuit uses a novel approach to produce a fully isolated and regulated 5
volts @30ma from the 120vac power line. It uses two tiny SCRs that alternately
discharge two capacitors through a miniature high frequency transformer. The
voltage spikes produced through the transformer are rectified, filtered and
regulated. A very common 8 ohm audio impedance matching transformer can be used
for the transformer. Published in EDN, Feb. 17, 1992
Run Switching Type AC Power Adapters on DC
I have received a couple emails from people looking for inexpensive DC to DC
converters, which can convert 40v to 60v DC into say +5 or +12v. Such
input voltages are often found in new automotive and industrial applications
with a typical DC voltage of 48 volts. It turns out that many, not all, but
many, standard AC line operated power adapters, which use switch mode
techniques, will indeed work great when supplied with DC instead of AC. The unit
below works down to about 30v DC and delivers 500ma at 5v. If you draw less
current, it will operate at even lower DC input voltages
