Project Logs

Collapse

• Test measurement: IR light to voltage

  canique • 03/28/2024 at 17:43 • 0 comments

  In a first test setup to measure the IR light as a voltage, the following simple circuit was used:

  VCC - IR emitter diode in reverse direction - (Testpoint T1) - 1M resistor - GND

  VCC is 2.814V

  IR emitter is a Vishay TSAL6200, max reverse current is specified with 10µA

  Note 2 things:

  1. We're not using a photodiode here which would have a higher sensitivity for IR light (it's just not available right now). An IR emitter can also act as a photodiode, although with decreased sensitivity.
  2. The multimeter that is attached to Testpoint T1 has a ~10M resistance, so a parallel resistor circuit is created here. The effective resistance is (R1xR2)/(R1+R2) = 0.91 MOhm

  Test results:

  When holding an Infrared emitter (IR remote control) very close to the TSAL6200 and while pressing buttons on the remote control, the max voltage at T1 is measured to be 770 mV. A scope would show more details here, and very probably a higher voltage.

  While nothing is pressed, under ambient light from a Philips LED (not IR), 0.13 mV is measured.
  

  If we change the 1M resistor to 7M5, the effective resistance is: 4.28 MOhm

  Test results:

  While the IR remote control is pressed 1140 mV are measured at max.

  While nothing is pressed, under ambient light from a Philips LED (not IR), 1.04 mV is measured.

  While holding my hand over the TSAL6200 and thereby creating a shadow, 0 mV are measured.

  Now we get an idea that even a bad receiver, which actually is an emitter, can produce a voltage of more than 1V when an IR emitter is placed only a few millimeters away.

View project log