Electronic – improve IR reciever

currentlight-sensoroptoelectronicsschematics

I have simple IR receiver without any modulators, which reacts for IR wave (940 nm) link , I connected it as on this schema
enter image description here

I beam on this receiver with laser diode with 650 nm lenght wave light.
It reacts, but I would like to improve this reaction.

Right now, when I don't blink there is 1.6 V bettwen IR receiver (LED is OFF), and when I blink with laser diode (650nm) there is 1.8 V (LED is ON)

The question is How can I improve the difference to be not only 0.2 V but much higher ? at least 1 or 2 Volts.

Best Answer

Without changing your general idea, you need to be aware that the voltage across an LED changes very little with current, once there is any current at all - such as room light will provide. The LED than acts as a clamp at about 1.6 to 1.8 volts. To get around this, try

schematic

simulate this circuit – Schematic created using CircuitLab

You will note that I have not included a resistor value. You will have to determine this yourself. In principle, you ought to be able to get a 2 volt swing easily, but you will not be able to get more than about 3 volts. Higher resistance will give greater sensitivity.