Testing and identifying Zeners

[smason]

Stumbled across this video, pretty good method of testing/identifying Zener diodes. This guy has a few good videos. Some are a bit dragged out, but good.

http://www.youtube.com/watch?v=5OcoF0nkgng

[retiredcaps]

Re: Testing and identifying Zeners

This guy has a few good videos.

I watch and participate in Martin's forum.

Some are a bit dragged out, but good.

Yes, none of his videos are brief or short so the people who can't sit still and concentrate will not find like his style.

[budm]

Re: Testing and identifying Zeners

At home I use variable power supply and about 1 K resistor in series with the DUT, just turn up the voltage (apply voltage in reverse bias) until the Zener voltage is reached.
I use curve tracer at work for testing.

[LLLlllou]

Re: Testing and identifying Zeners

Once when I was bored in my early teens I rewound a tiny 6v transformer out of an old radio with enough turns of fine wire to get about 40V out. I then fed this through a bridge and cap, to get some nice clean DC. Then I wired up an NPN transistor as a constant curent sourse of about 10ma. Put it all in an old watch box with a Radio Shack 1ma meter with a reistor shunt to show 50V full scale, and ran a couple wires out to aligator clips . . . walla . . . a no so instant zener diode tester.

Like I said, I was bored.


I still use it to this day some 20 odd years later.

[LLLlllou]

Re: Testing and identifying Zeners

Once when I was bored in my early teens I rewound a tiny 6v transformer out of an old radio with enough turns of fine wire to get about 40V out. I then fed this through a bridge and cap, to get some nice clean DC. Then I wired up an NPN transistor as a constant curent source of about 10ma. Put it all in an old watch box with a Radio Shack 1ma meter with a reistor shunt to show 50V full scale, and ran a couple wires out to aligator clips . . . walla . . . a no so instant zener diode tester.

Like I said, I was bored.


I still use it to this day some 20 odd years later.

Now that I think of it, it was actually a single FET constant current source like attached. Can't get much simpler. Wish I hadn't glued the watch box closed so I could see what part I used.

[LLLlllou]

Re: Testing and identifying Zeners

This is the one transistor current source I was thinking of, built quite a few of these for various nicad chargers over the years. Add a rotory switch with a few resistors and you can set the current for AAA AA C D and 9v batteries, 1 to as many cells as you want in series.

[budm]

Re: Testing and identifying Zeners

I use LM317 for constant current source for battery charge or just for current source, 1 resistor for setting the current.

[LLLlllou]

Re: Testing and identifying Zeners

I use LM317 for constant current source for battery charge or just for current source, 1 resistor for setting the current.

Simple and convenient (assuming you have some 317s laying around) but limited to 1A max and 35V supply. The above circuit has the advantage of working with just about any current and voltage you can find a transistor for. Not to mention it's esentially free using parts pulled from scrap boards. You can even add another diode in series and use a darlington power transistor for REALLY high currents.

[budm]

Re: Testing and identifying Zeners

I do have many many many LM317, LM338 in my stock. You can also add pass transistor for higher current source. The max. differential spec of 40V, so the max input voltage will be the 40V max across the LMXX + VLoad. I max 1.5A

https://cdn.badcaps-static.com/pdfs/...da6e24753a.pdf

[redwire]

Re: Testing and identifying Zeners

I'm using a disposable camera flash power supply (good for 300+VDC but only need 100V or so) and a two-transistor constant current source. It works pretty good, but the test current is important.
Some zeners are spec'd at 1mA, and others at 5mA. Crappy Diodes Inc. zeners have a mushy knee and are quite different Vz at lower currents.

[ben7]

Re: Testing and identifying Zeners

I'm using a disposable camera flash power supply (good for 300+VDC but only need 100V or so) and a two-transistor constant current source.

I don't have a fancy testing setup like that, but if I need to then yes that is exactly how i would do it!