Phototransistor question

Hi

I have a device that should be triggered by light. So, I took a simple phototransistor and transistor, soldered their collectors (and connected them to 12V source), emitter of phototrans. to the base of trans. and emitter of trans. out to the device. It kinda works, but not the way I'd like. :roll: The device needs 12V to operate, but the max. voltage 'behind' transistor (on its emitter) is cca 5.9V (with max. illumination of the phototrans.) Problem No.2: the transistor gets seriously hot after 5-15sec of operation. :shock:
Question: which transistor should I use? Phototrans. is OK. Trans. is of NPN type...
Oh yes, I tryed using a photodiode, but the voltage on emitter was even smaller (1.2-1.9V). :?:

Tenx

The simplest way to use a Phototransistor is to connect the emitter to ground, the collector to a resistor and the other side of the resistor to V+. The output is the collector of the phototransistor. Try 10Kohms to start.

Brent

You need to saturate the collector of the transistor in order for it not to get hot. The "darlington" connection you are using won't do that, so instead, connect the transistor emitter to ground and put the load from collector to V+. You will need a resistor in the collector of the photo transistor or else it will burn up. The value should give a base current that is 1/10 the collector current.

Ok, I'll try that! 8)

Tenx again!