[Updated] IR receiver emitter switch

I have made the circuit you see in photo using IR LED with 1,6V and 80 mA.
Used 56? resistor as I didn’t have smaller available. LED is shiny as I can see through cellphone.
For receiver 10K resistor.
I cannot see any changes in the voltage on pin3. I have checked with multimeter and with serial print.
What am I doing wrong?

It might be a good idea to post a circuit diagram & identify the receiver being used.

Also, describe what you are trying to achieve with your project and maybe upload the code for your sketch.

Otherwise, its dificult to help, without making guesses

Photodetector type phototransistor
Case 5mm
Wavelength of peak sensitivity 940nm
Collector-emitter voltage 30V
Viewing angle 30°
LED lens black with IR filter
Mounting THT
All I am trying is turn on and off a led using a wave with my hand. I am using plain two pin photodetectors not 3 pins.
I don't have a schematic yet

Phototransistor is of course connected correctly.
Looks like you added tape to mask it.. Try with a mirror.

Allready did, I have tried also without tape, with white paper with hand, with reflective board
Also tried pointing tip to tip .

If you have confirmed :

  • 5V at collector.
  • connection emitter/resistor os OK
  • measure 0V at this connection point when transitor get 'lots' of IR at +/- 900 nm

.. then that transistor is defective.

How about using a photodiode with a transimpedance amplifier?

Have you tried "tip to tip" AND inside of a cardboard box?
In ambient light, that phototransistor will always be ON.

Tried it in dark room. No sunlight no artificial light.
I have tried with different parts to make sure there is no defective parts.

I don't have a schematic yet

Put pencil to paper, take a picture of that with your camera (attach it or link to a picture site.)

I have tried with different parts to make sure there is no defective parts.

Then it's likely not the parts but the practice.

Here is the way things ought to be:

Still no solution…
After trying the variation you kindly suggested with no change I found on this blog exactly what I want to make.( light a led on pin 13 with a wave of my hand)

I applied this schematic and this code

int led = 13;
int IRSled = 5;
int IRRled = A1;
int val;

void setup() {

// initialize the digital pin as an output.
pinMode(led, OUTPUT);
pinMode(IRSled, OUTPUT); //IRS is InfraRedSender
pinMode(IRRled, INPUT); // initialize the infrared receiver

// the loop routine runs over and over again forever:
void loop() {

digitalWrite(led, LOW); // turn the LED off  (HIGH is the voltage level)
digitalWrite(IRSled, HIGH);


val = analogRead(IRRled);
 if (val <= 300) digitalWrite(led, HIGH);

Serial.print(" ");

Again my result is always HIGH I read a number of 887-890 an no matter what i do I cannot change that number. Not lower nor higher.


These are the datasheets of the IR led and receiver I am using,

that transistor is saturated always ? , even in complete darkness.
I believe it is defective..

I have 3 pcs of that and a couple of unknown origin wich also give me the same results.
I am absolutely buffled!

that schematic is what you have connected!
resistor <=10k , and U measure approx 4.4V.
If U disconnect analog input and still can measure that voltage to 4.4, there is a compunent defect.
test compunent with your Ohmmeter
The transistor can take 5V reverse without damage… try swap pins (its dead anyway…and u got a spare ?)

Indeed I measure 4.8V without the analog input pin.
What are the chances of all the photoconductors to be defective?

seller 'got balls' if he sold you 3 defective ones!
If all behave the same.. I'd try to switch pins.
Use the multimeter (diodetester) or Ohmmeter to measure both directions, with/without exposure to IR

OK I did that here are the results,
with regular ceiling light 0.631V
tip to tip with IR emmiter 0.598V
but when I place them next to each other(pointing at the the same direction) and try to reflect the beam with a mirror or my hand nothing happens to the Volt reading

with no light, the transistor should not conduct.
datasheet indicates no sensivity below 700nm, so room light shouldnt be enough

Your transistor conduct C->E with no light. To me, that means defective

try using your tv remote to see if that has any impact. Keep the button pressed and the remote's emitter right next to the sensor. (could help eliminate a faulty emitter or one with the wrong wavelength)