MPSA13G darlington combined with SHF 309 FA-3/4 phototransistor

[boylesg]

Without the 1k resistors in the above circuit and a 47R resistor connected between the MPSA13G's emitter and GND, I am getting a good range (but 2V to 3V) with reflected IR from my hand. However I am getting around 50mA running through the resistor, which is not really acceptable given there will be a total of 10 of these circuits forming two crude compound eyes and running off a battery pack.I am trying to reduce the current to less than 1mA but preserve the voltage range. But the 1k resistors in the above circuit don't achieve this.How would you achieve this folks? I can't seem to figure it out on my bread board.

 

[godfreyl]

I think you drew the circuit wrong. Is the collector of mpsa13g supposed to be connected to battery minus, as shown? Which end of the battery is connected to "ground"?

 

[boylesg]

I think you drew the circuit wrong. Is the collector of mpsa13g supposed to be connected to battery minus, as shown? Which end of the battery is connected to "ground"?

Sorry, it was indeed meant to be connected to the battery positive.- - - Updated - - -I think I figured it out.A 10M resistor between the phototransistor and darlington base and then a 1.5k resistor from the darlington emitter to GND.I get an increased voltage range from 2V or so down to around 1V with my hand reflecting IR.I could reverse that voltage range with a BC559 so increasing voltage means decreasing distance from the phototransistor.

 

[Audioguru]

50mA in a 1k resistor needs a voltage across the resistor of 50mA x 1k= 50V that you do not have. The resistor would heat with 50V x 50mA= 2.5W.
So your math is wrong.

 

[godfreyl]

So your math is wrong.

No, the 50mA was with a 47 Ohm resistor. Anyway he's got the problem sorted out now.