Light Up Leggings

Step 2: The Circuit

Plan out your circuit on paper first.

Each leg is a separate circuit with 6 LEDs.  The LEDs are wired in parallel.  The rest of the circuit is in the back of the leggings.

This circuit can be transfered onto a t-shirt, bracelet, you name it!
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NoseyNick4 years ago
They SHOULD be in series. You don't want to put multiple LEDs in parallel on one resistor - you'll find the small manufacturing differences in the LED forward voltages will essentially mean one or two of the LEDs will hog almost all the current and the others will be too dim.

If you connect them in series, they all share the same current so will all be approximately the same brightness, however you'll have to add up the total forward-voltage, and subtract from the supply voltage (which must be greater) to determine the best value for the current-limiting resistor.

... then, if you wish, you can put several of THOSE CHAINS (each with their own resistor) in parallel if you wanted more LEDs.

EG:

+ LED LED LED LED LED LED RESISTOR -
+ LED LED LED LED LED LED RESISTOR -
+ LED LED LED LED LED LED RESISTOR -

4 years ago
Actually, I've done some maths... IF you're running off +3V, you don't have enough voltage to break the forward-voltage of 6 in series. Typical forward-voltage of a red LED is about 1.7V-2V, leaving about 1V from your 3V supply. 1V across a 221ohm resistor gives about 5mA, which is pretty low even for one LED, but even worse divided between 6 in parallel, especially if the one with the lowest forward-voltage steals almost all the current off the others. Really you'd need one resistor per LED, then connect the resistor-LEDs in parallel, like:

+ LED resistor -

+ LED resistor -

+ LED resistor -

[etc etc]

Alternatively, find yourself something like a 9V battery, then you could do:

+ LED LED LED resistor -

+ LED LED LED resistor -

+ LED LED LED resistor -

[etc etc]

... with (let me see) (9V-2V-2V-2V)/0.1A = 300ohm resistors

LongToe4 years ago
Looks Great! It would be good for Halloween too.

Not to be overly critical but if I remember circuits correctly, one of the sketches shows the LEDs in series rather than parallel. Perhaps that was part of the design process.
4 years ago
Yes, the first one is in series.