Arduino input impedance causing problems

Hello all
I am tying to build a simple circuit which consists of an array of 5 optical sensor TCRT5000 with a 10K Ohm resistor connected to its emitter to the GND.
When a single optical sensor is connected to the arduino digital input, I can get 0V and 5V output from the sensor. But when I connect the second or third sensors to the Arduino digital inputs, it makes the voltage to drop to 1,9V. So I ask you: is the digital input ports operating at low impedance? Are these digital ports isolated from each other? Thank you!

Cannot see any reason why those optos should not work, so suggests you post a diagram of your actual circuit and the code showing how you have set your input pins.

If the pin is selected as an INPUT (the default at reset) it will not be drawing any current (unless you've
fried the chip somehow).

Input resistance of a CMOS chip is typically 10^10 ohms or more at room temperature.

But when I connect the second or third sensors to the Arduino digital inputs, it makes the voltage to drop to 1,9V.

Is this a different digital pin for each sensor - it needs to be.
Do you have a resistor in the LED side of the sensor - you need to have.

The I/R light from the various sensors may be affecting each other, or ambient light may be affecting the phototransistors, depending on the optical/mechanical set-up. It that's a possibility, try covering all of the sensors with black electrical tape to see if they all go to 5V.

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

We need to see what you mean exactly by;

I am tying to build a simple circuit which consists of an array of 5 optical sensor TCRT5000 with a 10K Ohm resistor connected to its emitter to the GND.

Thanks.. Tom... :slight_smile: