Infrared Leds - Analog input

Hello, I'm using 50 leds infrared emitters connected in parallel fed by 3 volts, 20mA each, connected an external source. Also, separately, I'm using 50 infrared leds other receivers, which are connected in series and connected to the Arduino UNO (the downside of Arduino and the GND point on the positive analog input A0. "

The idea is to place the 50 LEDs emitting leds facing the 50 receivers at a distance of approximately 50 cm. That would give me a maximum voltage value on port A0 Arduino.

Putting a barrier, covering led by led, I would be having less light reception by leds receptors, thus gradually decrease the tension.

The problem is that the LEDs receptors themselves generate voltage (not need to be fed) but does not generate current. Thus, the receiver 50 concatenated LEDs generate approximately 20 volts, but a current equal to zero.

The questions are: 1 - As the Arduino analog ports only receive a maximum of up to 5 volts, 20 volts and decrease to 5 volts that this circuit has no electrical current? No use of a resistor in series, because it does not affect anything.

2 - Even with constant light and stable system, the port value A0 varies greatly, ranging to about 2 volts and more for less at a frequency of approximately 1 second. Could someone explain to me why this occurs and how to solve?

Thank you for your help, Nyck

I've just removed the three identical copies of this post.

DO NOT CROSS-POST.

It makes me CROSS.