Hi new member here and hoping somone can answer what is probably a simple question to the experienced. I am making a model project and am lightng LEDs using a nano and a ULN2803 transistor array. I am using high brightness LEDs and want to drive them at around 25mA.
At 5v and using a 68ohm resistor i get 26mA running the LED direct. Now when I connect into the circuit with the nano and ULN2803 the LED is only getting 17mA. I assume this is due to the internal resistance of the ULN chip. Will I run into any problems if I just reduce the resistor so I achieve my 25mA.
Many thanks for any advice
Dave
In reply to Hii by Sourav Gupta
Thanks
I will be running 3 LEDs in parralel with their own resistor from each output pin across all 8 outputs so 600mA total. I have read that a MOSFET would be more efficient in this application, what would be a suitable logic level MOSFET array that would drop right in instead of the 2803?
It will not cause problem because each individual Darlington pairs have maximum current of 500mA, 50 V. TPL7407L is a 7-channel Mosfet array equivalent to it, speced with 600mA drain current, 40V.
Sourav Gupta
Joined February 12, 2018 696Monday at 02:11 PM
The Darlington pairs are rated for 500mA 50V output. It wouldn't be a problem but the 2803 will heat up.