Our example schematic September 2014 | PlanetChristmas 23 bulk where you can. I calculated the resistor sizes needed for each of my strings based on the number of LEDs and voltage differences based on color. I then purchased resistors with a value common to all of my strings, but within the closest range of my of my requirements. This allows me to use the same resistors for most strings, and I commonly only use two different resistor sizes. For example, I have purchased both 3.6K ohm/2 watt and 2.7K ohm/2 watt resistors for all of my strings. I may use one, two, or a combination of these values depending on my needs. Shortening the LED string using meter option 1. Cut the string to the length needed 2. Connect the multimeter in series on the wire you just cut 3. Set the meter to milliamperes 4. Power lights on and record the reading 5. Power down, remove extra lights 6. Now connect multimeter and potentiom-eter in series 7. Set the potentiometer to its highest set-ting (50K ohms) 8. Turn potentiometer down slowly until there is a match in the milliamperes read-ing recorded earlier 9. Power down, remove pot and measure the resistance across the potentiometer in ohms 10. Place a resister the same size as measured in reading above, always select the next highest resister value, solder and shrink wrap all TIPS: 1. Do not shorten your string too far 2. Watch for the power dissipation with resister 3. Be extremely cautious you are working with live power 4. Buy a meter that is capable to do all the above requirements. More hands on Start by becoming familiar with the sche-matic at the top of the page. Note the diodes and resistor at each end (J1 and P1.) Building the Strings You’ll need some parts. • 4 x 1N4005 diodes • 2 x 3.6K ohm/2 watt resistors • LED string shortened to 26 count 1. In my example, I am shortening a string of red LEDS to only use 26 LEDs and still allow AC voltage to pass through to the female plug end (J1) above. 2. Cut off and retain the male and female plug ends. Discard any existing rectifiers (blobs) that came with your strings. 3. Shorten the string to the number of LEDs you require. Note: this is dependant upon your need. 4. Assemble the male and female end recti-fier components (2 x diodes, 1 x resistor for each end). Tin the ends and solder the diodes together and the resistor in place. Note: you can place the resistors at any location within the rectifier. When using two, I place one on each end of the cir-cuit, this is just my preference. Reference the below image for proper orientation of the diodes in relation to the male and female ends as well as connection to LED strings. Also reference schematic above.
PlanetChristmas Magazine September 2014
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