ULN2003APG driven LEDs

[Divya Raibagkar]

Hello everyone,
i am doing a project named as "Non invasive system for blood pathology" , the schematic which i have drawn is as shown in figure. I just wanted to know whether the circuit will work as i have desired. i have written a code for sequence glow of leds, but get erroneous results through LDR. plz help me out......... any valuable suggestions are welcomed.
waiting for replay.

 

[Vbase]

There has to be a resistor in series to each LED. The value can be 220R up to 2.2K. The resistor determines the current through the LED. without the resistor the LED can be damaged or the 5V supply overloaded and voltage collapses.
You can start with 2.2K and if the LED is too dim reduce the resistance.

 

[Divya Raibagkar]

+Vbase ,
actually you caught me right.
We are facing the same problem. Our LEDs are getting damaged.
Thank you for your suggestion.

 

[Vbase]

If the LEDs are 5mm indicators then you can save yourself the ULN2003 because the arduino can source up to 25mA, normal LED needs 10mA.