I am reading a hex code from an IR receiver. My objective is that when Arduino receives a code, it should drive ULN2003A to operate a relay. But my problem is that I am not getting 5v from arduino Output pin, the voltmeter reading is only 1.9 v which is not sufficient to drive ULN2003A.
What will be the solution for above problem? Please help.
What will be the solution for above problem?
Post some code.
Post a schematic.
Only then can we determine why your output pin is so low. The most likely reason is that you are trying to draw way too much current.
I suspect that the OP neglected to configure the pin as an output.
tmd3:
I suspect that the OP neglected to configure the pin as an output.
Agreed.
Sounds like a floating voltage.
OP:
pinMode(3, OUTPUT);
I'm thinking he is missing a resistor.
Paul__B:
I'm thinking he is missing a resistor.
He doesn't need one if he's quoted the right part number. TI's datasheet declares that, "The ULx2003A devices have a 2.7kΩ series base resistor for each Darlington pair for operation directly with TTL or 5V CMOS devices."
Johnny010:
Sounds like a floating voltage.
No, it's not "floating".
If you leave the pin defined as an input and write it HIGH, you are enabling the internal pull-up - about 50 k to Vcc.
That would explain the low voltage.
The ULN2003 is of course, a bad choice, essentially an obsolete device.