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Playing with Schottkey

Playing with Schottkey

I just got some SB540 Schottky diodes, those are about 40 V at 5 A. I was interested in the reverse leakage, as that can be high for diodes like this. So I made a simple test circuit, and was actually amazed how much it changes around room temperature. I mean from 7 uA at 25 C to 11.2 uA at 37 C (touching it). That is a LOT, and makes for a nice temperature sensor.

So I made this: + 9V + 9V | | | R 82 Ohm | | | k LED Schottkey SB540 | | a c -------------- b BC547B (beta around 300) e | ///

Nice fridge alarm :-)

Maybe better than a NTC in this temperature range?

Reply to
Jan Panteltje
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Not to rain on your parade, but the world isn't particularly short of uncalibrated nonlinear temperature sensors.

..maybe put it in series with an LED for a 'hot enough to burn human flesh' warning?

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

On a sunny day (Tue, 26 Apr 2011 08:50:34 -0400) it happened Spehro Pefhany wrote in :

Not to disagree, but I just calibrated it did not I?

Or global warming :-)

Reply to
Jan Panteltje

Not to be disagreeable, but your invaluable time calibrating it probably increased the cost to a large multiple of the cost of the raw part (15 cents?).

I wonder where we could stick them that would be sensitive enough?

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

Hello Jan,

This isn't strange,

The reverse current doubles each 8..10 K increase in temperature. Normally you don't notice this (as for PN junction diodes, leakage can mostly be ignored [many exceptions]), but in schottky rectifiers, low conduction loss results in high reverse current.

Wim PA3DJS

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Reply to
Wimpie

Jeez, next you're going to point out that using glass-encased diodes as photodetectors isn't exactly solving a pressing world problem either. :-)

Using LEDs as both a photo source and as a (rather lousy) detector to build bi-directional data links *is* cool, though.

Reply to
Joel Koltner

No, but using it that way inadvertently could cause problems, like causing an H-bridge to vaporize when you take a flash photograph of the controller. ;-)

It's cool. What interesting variations are there with different wavelength/color LEDs?

Reply to
Spehro Pefhany

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