User Manual

21
Required parts: 9V battery*, 1K resistor (brown black red gold), red LED, green LED, wire
jumper
How it works: When the 9V battery is con-
nected to the circuit with the right
polarity the green LED (good) will light up.
Current can ow from the "+" of the battery
through the green LED and via the resistor
back to the "–" of the battery. The red LED
(wrong) will not light up as it is polarised in
the opposite direction.
When swapping the connection of the bat-
tery (switch the red and the black wires)
the red LED will light up. This way we can
determine whether a battery is connected
the right way or not.
GREEN RED