Phototransistor for a DIY shutter tester

naeroscatu · Jan 15, 2009

Hi folks,
I went yesterday to a pretty good electronic parts store in the city looking for a phototransistor BPW 40 or similar and I was told a) they don't have it need to order then b) I need to order minimum 15 of them.
What would I do with 15 phototransistors when I need one? Any of you has such a component lying around without use? Many thanks

keithwms · Jan 15, 2009

Diwan Bhathal showed me his clever shutter tester and it's based on sound only, as I recall.

Anyway, yeah, I think I actually do have some phototransistors lying around the lab. But the response times are not good enough as I recall.

archphoto · Jan 15, 2009

I got a phototransistor for you, but it is in Holland and I am in Brazil.
I have used this phototransistor in my own designed and build shutterspeedtester. It is the NPN type (the one I have)

Please send me am email with your full name and adress and can get it to you.

Peter Morisson archphoto@aol.nl

Mike Wilde · Jan 15, 2009

was this sayal?

the Sayal group are usually ok with finding the ones and twos they have in thier group of distribution centres in the GTA.

I bought a IR detector, and a couple of different power IR transmitters as single unts from them a few years ago. The plan was to make a flash trigger to take pictures of water drops. It has not made it past the breadboard stage, but the concept of operations was valid.

As I recall, the detector was a phototransistor; used with the IR transmitter running off a battery with a resistor as a current limiter should work to trigger the light as it travels though the shutter while it is open.

The other option is a marked up disk of paper making a pattern wheel and running it on a turntable, spinning at a known rate. With the right number of identifiable strobe lines you can count how long the shutter was open by seeing how much the image is smeared in the exposed neg. This was an early Leitz shutter calibration means, I believe.

rexp · Jan 15, 2009

Photodiodes are faster, giving you much cleaner rise/fall times. PM me a mailing address & I will send you one or two.
(please remember, I don't check this site every day, but I will get back to you)

naeroscatu · Jan 15, 2009

REXP, email sent. many thanks to all for your support on this.
Mike - yes, it was Sayal. They have other types of photodiodes which I'm not sure will work with this application (I'm no expert in electronics) plus I have to order, plus they sell min 15 pcs. Otherwise the store is pretty good.
Peter, thanks for your offer.

Greg_E · Jan 15, 2009

There was a bunch of talk on this subject on the Yahoo Camera-fix group. The diode recommended was a faily low cost device that you could order from Mouser or Newark electronics (one of those two has an office in Canada so it would be easier for you to order). In order to get the speed, the diode had to be reverse biased to a certain voltage (I think it was either +5 or +9 volts). When the light hits it it avalanches and conducts. So I built a board with 9 superbright LEDs and then hooked the diode to an oscilloscope to measure the time it was conducting. Works really well. Not sure if I have any of those part numbers, but I do remember the total price was around $10, but you would need a cheap oscope to go with it (another $100 to $150).

If you do a search you can see pictures of the one that I built, might have even given the part number for the diode.

bspeed · Jan 15, 2009

PM me, and I will send you one. I ordered a few extra for my tester.
or better yet, I will pm you!

dans · Jan 16, 2009

A lot of Ham's and other experimenters use a place called digikey and mouser (google them).

Dan

Ralph Javins · Jan 16, 2009

Good morning;

The device that I used was a Texas Instruments manufacturered JEDEC type number 1N2175 photodiode. It is a glass tube about 1/2 inch long and about 1/16 inch in diameter with a hemispherical lens at one end and two very small wire leads coming out the other end. For our purpose, it has a very fast rise time. If needed, I can probably find the data for maximum voltage and maximum light current in one of the books in storage. Select a current limiting resistor to work with your power supply (5, 6, 9, or 12 VDC) and hold the current to one or two milliamperes DC and it will work fine with any electronic counter or calibrated oscilloscope.

Phototransistor for a DIY shutter tester

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