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How can I wire LEDS this way? Answered

Im looking to make a sort of contact on/off switch for a bunch of wired leds. lets say when it is in "contact" the leds will be off and when the "contact" is broken the leds will turn on. Im also looking to have a different set of leds that will be on constantly. What is this best way to do this and what materials will I need? THANKS


Or you could buy christmas lights. :]

easy and very inefficient solution if the amount of leds is small (one series link with its own resistor that is about 100 ohm at least) just short the leds leaving only the resistor in the circuit good solution wire the leds as normal. in the - side dont connect the leds to the source -. get npn transistor that is ok for the voltage and current in the circuit. for example up to about 18 V 0.1 A you can use C945 which is very common in electronics you can find in the trash connect - of the leds to C of the txistor connect - of the supply to E of the txistor the txistor needs resistor too. treate the txistor as a led. the source voltage is your supply voltage. the txistor voltage is 0.7 V. the txistor current is the recommendrd base current in the txistor datasheet (pdf file you can find online) connect + of the supply to the resistor and from it to B of the txistor circuit should work now but the txistor should remain cool and not heat up. if it heats maybe it is overloaded or the resistor you calculated for it is too small connect your switch between B of txistor and - of supply

instructables variation of

txistor = transistor
txformer = transformer