Computer-based shutter speed tester

VeroBoard Layout & Components

The circuit includes 4 components plus the connections to the parallel port.

All this can be done on a small piece of VeroBoard or project board. The diagram below shows the veroboard from the top. The copper links between the holes are on the reverse side of the board. That is where the soldering is done. So beg a small piece of board from a friend/colleague - about 10 holes x 10 holes will do.

The Photodiode and transistor can be obtained from most electronic stores. The BC212 transistor can be replaced with a similar one such as the BC327, BC328, BC556 or BC557. The legs of all these are the same as in the diagram. Radio Shack has a 2N4401 but its legs are a bit different. The diagram shows

c b e

with the flat face up. The 2N4401 has

e b c

with the flat face up. You have to make sure you stick the correct leg in the correct hole as is shown on the verboard schematic.

The photoDiode or Phototransistor should be easy to get and it does not matter much about which type it is. The one I used was scavenged from a dead Video player. They are used to detect action and stop a component.

You will also need a D25 male plug for the parallel port on the computer and some sort of connection for the detection end. This will be linked by something like a strip of ribbon cable. You will need a long enough piece of ribbon cable to be able to run from the computer to the surface on which you do the testing. Anyone you know that plays around with computers, should have both a plug and some cable lying around for you to scavenge.

The Variable Resistor is any old 10k miniature pot (potentiometer). Radioshack has them. And the resistor is a simple 1/4 watt 5% carbon-film resistor.

And you will need some wire to link things up.