Help needed with Phototransistor L14G3

[yasser11]

Hi

I am using photodiode TIL 38 as an infrared source and using L14G3 as a detector. Between the diode and the detector I am keeping my finger so that the output at collector will vary according to the change in blood volume in the finger. By this i intend to measure the heart rate.

Can anyone help me in biasing the ckt. because I think I am not biaising it correctly. I am unable to get any output at the collector(it's totally random and no way near to what I am expecting) , also sometimes 50Hz wave (power supply noise) comes at the collector.

If anybody has any idea how to overcome these problems then do reply.

 

[audioguru]

Since you didn't attach your schematic then we can't troubleshoot your circuit.
There are a few projects like that on a search in Google. One explains how the phototransistor must be shielded from the flickering of AC lights.

 

[Nigel Goodwin]

Google for 'hemon' a PIC based project, it includes just such a sensor.