It does not use a isolation step down transformer. This has to be constructed only by skilled people with knowledge of safety requirements.
Meter with LED Analog Bar
C1 limits the current and drops most of the voltage. The zener regulated supply is for the chip. C2 can be raised to 220uF or more if required. The bar mode display may consume more power. Use dot mode only on capacitor power. Bar mode will need a bigger cap or a transformer supply.
- Versatile and Easy use Display
R2-R3-R5-R6 form a voltage divider to get a sample of the input voltage, D11-C3 get the DC value.
Adjust R5 preset with a log Plastic tweaker to get the 5th
led to just turn on when input voltage is at 138V 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 for study
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.
Back to Mains Voltage and Power
20th May 2020
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