LED light string
For the LED string project we
will require:
LEDS: different colours (maybe also shapes, sizes)
Wire: thin and flexible
Heatshrink: to cover the
solder joints
Solder: to join the LEDS, resistors
Resistors: low wattage ¼ or ½ - perform
calculations prior to purchase
Power Supply: could be mains or battery etc. 12V is common,
choose current rating after deciding number and brightness of strings of LEDS.
We will be having parallel strings of serially connected LEDS and resistor
combinations.
Circuit:
Create strings with 3 or 4 LEDs
with same polarity in each string – test each string. Good to use similar type LEDs in a given string. The physical location of the diodes
in the resulting light string does not matter. Each diode type tends to have a it’s own given voltage drop and maximum current.
Circuit
Diagram with symbols:
Maths -> to calculate the
resistor values:
We know, maybe we don’t so we
will create a test circuit with one LED and a suitable resistor and measure
some values.
Connect a 1000 Ohm resistor (1/4
or ½ Watt) to an LED and connect the ends of this combination across a 9Volt
battery. The combination will work one way and not the other – by work we will
see the LED shine. If it does not work one way reverse the battery polarity, (i.e.
connect the circuit the other way round). You will notice, in the round
(cylindrical with a spherical dome really) LEDs that
there is a flat side on the LED flange and one leg will be shorter than the
other.
Sunday, 6 September 2009