Voila a photo-transistor !

Still looking at the pulse sensor for the exercise computer (see 2-17-22 post) I looked through my inventory of parts and junk for photodiodes and phototransistors.  I did find some photodiodes and in a pinch an LED or a glass bodied diode might also function as a photodiode.

But no phototransistors were found (at least none that were labeled as such).  

I could buy some photo-transistors but then there is that delay factor where when you finally receive something you've already moved onto some other project, the purchased item gets shelved and some time later upon finding the purchased item  you wonder:  "why did I buy this ?" :)

So after some internet searches I realized that a metal can transistor could be converted to a photo-transistor by removing some of the metal.  After finding a bag of 20 2n2222 metal can transistors from Central Semiconductor I then got a coping saw and set to work.  I sawed through the can to where I could fit the tip of my diagonal cutters and then peeled back the top of the can.  The can is made of a mild steel. I figured it would be better to peel off the top rather than generate a lot of tiny filings that might cause mischief.

Here the emitter is on the right, the base on the left and the collector is connected to the gold plated plate (and case):

Then the opened transistor was tested and still seems to function according to one of those little testers from Ebay (hfe about 100, Vbe about 700 mV).  The BE junction generates over 400 mV when a desk lamp is trained on the die.

About this time I started to get cold feet (literally) so decided to quit for the day.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm