HowTo-Color (8) / Hacking Electronics / Simon Monk / 236-3 / Chapter 4
CHAPTER 4: LEDs
(a)
67
(b)
Set the variable resistor to its middle point and wire up the breadboard as shown in Figure 4-15b. You will probably have to move the positive lead of your multimeter to a different socket when measuring current. Select a current range of 200mA DC. Now adjust the variable resistor until the current reads 20mA. We can now measure the voltage across the LED. To do this, first disconnect the multimeter, put the positive multimeter back in the right socket for measuring voltage, and then change the range to 20V DC. Wire it up as shown in Figure 4-15c and measure the voltage. In this case, it was 1.98V.
(c) Figure 4-15 Measuring the forward voltage of an LED
You Will Need Quantity
Names
1
04-ch04.indd 67
Item
Appendix Code
Solderless breadboard
T5
1
D1
LED
K1
3
R1
500Ω trimpot
R3
Jumper wires
T6
1
4 × AA battery holder
H1
1
Battery clip
H2
4
AA batteries
12/29/12 2:11 PM
