Hi,
Im looking for a fototransistor for ambient light. I've found one type RPM-075PTT86 at digi-key, but it's a bit beyond my soldering skills. There are plenty of fototransistors that are tuned to the ir range so I'm wondering if those will work. If not, will adding a ir absorbant filter do the trick?
Llafriel
Im looking for a fototransistor for ambient light. I've found one type RPM-075PTT86 at digi-key, but it's a bit beyond my soldering skills. There are plenty of fototransistors that are tuned to the ir range so I'm wondering if those will work. If not, will adding a ir absorbant filter do the trick?
Llafriel
Silicon photo transistors have peak sensitivity to the near infra red and can hardly see blue light. The (black) package is designed to block visible light so adding an infrar red blocking filter will end up with nothing.
If you just want to experiment, carefully cut the top off a TO-18 transistor eg bc108.
If you just want to experiment, carefully cut the top off a TO-18 transistor eg bc108.
Maybe this one?
http://www.elfa.se/elfa-bin/setpage...a-bin/dyndok.pl?lang=se&vat=0&dok=2021364.htm
(Sorry it is in swedish, but that should be OK for the threadstarter, I hope.)
http://www.elfa.se/elfa-bin/setpage...a-bin/dyndok.pl?lang=se&vat=0&dok=2021364.htm
(Sorry it is in swedish, but that should be OK for the threadstarter, I hope.)
Thanks for the replies guys. The elfa kind is a good example of what I'm thinking about. It responds to visible light but peaks in the ir range. Will I be able to measure ambient light with this, ranging from darkness to daylight?
I'll probably use a photocell though, but what are their response above 100 lux? Daylight in a room is more than 100 lux isn't it?
I'll probably use a photocell though, but what are their response above 100 lux? Daylight in a room is more than 100 lux isn't it?
A plain photo transistor will work in daylight. The only light source which have not much IR is "lysrör" tube??? lamps.
If you want a sensitive transistor it must be a with the base connected. You must also connect the transistor in class A in order to increase the light gain.
I work commercially with designing photocell equipment so I know some.
If you want to do some experimenting I have my drawers full of photo transistors. I will check what I have.
If you want a sensitive transistor it must be a with the base connected. You must also connect the transistor in class A in order to increase the light gain.
I work commercially with designing photocell equipment so I know some.
If you want to do some experimenting I have my drawers full of photo transistors. I will check what I have.
Christer said:
this is in english ( lang=en )
http://www.elfa.se/elfa-bin/dyndok.pl?lang=en&vat=0&dok=2021364.htm
A CDS photcell is definitley the simplest way to go. Try the Clairex or EG&G Vactec websites. There are application notes there. You can also try searching the links at www.epanorama.net . Lots of good stuff there.
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