Simple Mains Voltage monitor LM324
This Circuit helps in the monitoring of mains
supply voltage. Four LEDs driven by LM324 used as
a Comparator, A potential divider creates
It does not use a isolation step down
transformer. This has to be constructed only by
skilled people with knowledge of safety
Monitor for your Boat or Car
C1 0.47uF can be brought down to 0.22uF for low
LED currents, use high efficiency ultra bright
LEDs.C1 should be 440V AC or 630V DC plastic axial
yellow, polyester, polycarbonate, polypropylene,
R3-R6-R9-R14-R18 resistor divider determines the
LED turn on or threshold switch points, 10M for
Measurement Analog LED Meter
Adjust R16 preset with a log Plastic tweaker to
get the led D2 to turn on when input voltage is at
220V AC. This has to be done after PCB is put in a
sealed fire-retardant-plastic or epoxy box. drill
a hole in box for plastic tweaker.
This Circuit is Not a Tested Design. It is an Idea
This Circuit is Mains Operated without Isolation
Transformer and will give lethal electric shock if
touched when the circuit is turned on. Test
circuit only with DC 9V Bench Power Supply to try
it out. Do not use 230V AC.
Battery Level Indicator
- Similar Circuit
that is used to measure Low DC Voltage like a
When you use a capacitor powered supply you get a
small current but no heating. Resistor based power
has even lower current and there is heating. These
are very low power encapsulated devices only.
Transformer based supplies are safe and generate
very less heat and can deliver much more current.
The Size of transformer increases with current.
Finally we have SMPS the most popular with
moderate heating and small size even for large
currents. Then SMPS have to be designed for high
reliability. There were Thyristor based power
supplies but they are largely replaced with Mosfet
and IGBT based ones.