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Friday, 18 April 2014

ULN2803 - Darlington Pair IC For Controlling High Current Devices

by realfinetime  |  in uln2803 at  09:35

If we want to control a motor or relay using a microcontroller, we have to use driver ICs such as ULN2803 or ULN2003 because each digital output pin of arduino can sink or source only 40 mA. If motor is connected directly to the digital output of arduino pin, board get damaged due to overload.

Pinout diagram of ULN2803 is given below.

ULN2803 has eight darlingtons with common emitters. Each darlington can hold load current upto 500 mA. Chip is capable of handling output voltage of 50V. Inputs and outputs are pinned opposite to each other to simplify the circuit. Output pins can be parallelled for higher current rating.

Circuit diagram to control nine parallelly connected LEDs using Arduino and ULN2803 is given below.

LED bank will turn on if  the state of  PIN13 of Arduino is HIGH. Eight such LED banks can be controlled using a single IC.



All the circuits, published in this blog is only after testing and getting proper results in my private lab. When you try these circuits, you should check the supply voltage, polarity of components, presence of childrens nearby and shorts in the circuits. This website will not be responsible for any harm happened to you or your components caused by your carelessness.

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