0 simple voltage probe

This is a very simple probe or tester for any voltages both AC and DC from 2.5V to 230V. What this circuit do is help us know if know if there are any voltages in batteries, wall socket, inverters, conductors or current carrying wires. Another is it help us estimate the magnitude of the voltage thus giving us idea not to touch it.

voltage probe diagram

Part List:
Bulb - 5W incandescent bulb (220V to 230V rated)
LED1 - red LED 3mm or 5mm (see pinouts below)
LED2 - yellow LED 3mm or 5mm (see pinouts below)
Probe 1 - red or positive probe
Probe 2 - black or negative probe

LED pins and symbol

When Voltage is less than 90V DC, only one led is on. IF red or positive probe is connected to positive of DC supply, only LED2 (yellow) is on, but when probe is reversed LED1 (red) is on. If voltage is more than 90V DC one LED and bulb is on.
When voltage is less than 90V AC, the two led are on regardless of the polarity of the probe. When voltage is between 90V to 230V AC, both LEDs and bulb is on. Summary of the testing base on our result is tabulated below.

LEDs and bulb response to diff voltages

Take note that below 90V does not mean that the bulb will not glow at all (result is based on our observation).  The general idea is, as the voltage increases, so is the bulb brightness.

Note: As tested, the probe can be used in 230V max. Voltage at this magnitude is dangerous so think of your safety first. Keep in mind also that when both LED and bulb is off, doest necessarily means that there is no voltage at all, there are cases where LED is defective thus it will not light up.