I would like to design this circuit shown in the picture. I have simulated it in Multisim. It functions as follows: When the switch is open, the phototransistor is high impedance, when the switch is closed it is low impedance. I wonder how to input this into Multisim. I would like to adjust current on phototransistor according to distance between photodiode and phototransistor. For example: if the distance is 1 metre, current on phototransistor is 10 mA; if distance is 2 m current on phototransistor is 4 mA. I have not found out how to do this in Multisim. Do you know how to do it in Multisim or do you know other software where this is possible?
You cannot use a photodiode to trigger a phototransistor.
A photodiode is another kind of light detector, with a similar function to a phototransistor. It cannot be used to generate light (without damaging it). A diode that emits light is rather unimaginatively called a light-emitting diode or LED.