Re: Another H1812 source

On Sun, 21 Jul 2002 00:27:06 -0500, Joe Bachmann <joe.bachmann@newmail.net>
wrote:

>Rodger,
>
>Good point, that probably wouldn't be enough for a HV diode that we are using.
>But, the drawing you gave will only test that the diode is conducting one
>direction or the other. Using that method the diode could be shorted. So, we
>would need to use DC to run this, not AC. Just adding in a simple bridge
>rectifier with a decent filter cap should be enough. You will of course need to
>test the diode both directions in the circuit.

This is what AC does for you. As Rodger stated a good diode would only light
one side of the neon bulb. A shorted (or leaky) diode would light both sides,
an open diode would light neither. You can't just look at if the light is lit
or not, you have to look at *how* the light is lit.

Though as a disclaimer I've never used a neon light to test a HV diode.

-Zonn

>I can draw this up in a quick pdf if anyone would like to see it, but maybe
>someone could do a nice ascii of it.
>
>JB
>
>Rodger Boots wrote:
>
>> Joe Bachmann wrote:
>>
>> > The HV diode can be tested with a DC power supply (even a wall adapter of
>> > at least 12 or 15 V output), series resistor (to limit current), and your
>> > multimeter. This will determine proper behavior, at least at low
>> > voltages.
>> > The following is the schematic of a simple HV diode tester:
>> > 240 ohms, 1 W
>> > + o-----------/\/\---------+------------o +
>> > |
>> > __|__ HV Good: 6 to 10 V
>> > 15 VDC _\_/_ diode Shorted: 0 to 2 V
>> > | Open or reversed: 15 V
>> > |
>> > - o------------------------+------------o -
>> > The voltage drop in the forward direction should be at least 6 V with
>> > a few
>> > mA of current but may be somewhat higher (8 V or more) with a few
>> > hundred mA.
>> > If your DMM or VOM has a resistance scale operated off a battery of at
>> > least
>> > 6 V, you may get a reading in one direction (but only one) without the
>> > need
>> > for an external power supply.
>>
>> Yikes! Maximum RMS current is 4.6 mA and maximum voltage drop with 5 mA
>> current is speced at 85 volts for the H1812.
>>
>> Your conditions would work for something like a microwave oven diode,
>> which can actually handle "a few hundred mA".
>>
>> Let's try something else (if this doesn't look right highlight the
>> entire email and select "fixed width font"):
>>
>> ___
>> _ 33 Kohms / Ø \ NE-83 or NE-2
>> ___| \ ___/\/\/\_____/_| |_\_________
>> | \ \ | | /
>> 115 volts | ) \___/ To diode
>> Wide prong --> ___| /______________________________
>> |_/
>>
>>
>> The "wide prong" of the plug should be the neutral (closest thing to
>> ground to come out of the wall outlet), but please only connect or
>> disconnect the diode with the power disconnected..
>>
>> The resistor limits maximum current to protect both the neon bulb and
>> the diode. An NE-83 will be more sensitive, but any version of an NE-2
>> should work, especially if not kept totally in the dark.
>>
>> A good diode will cause only one electrode in the bulb to light. If
>> both electrodes light the diode is either leaky or shorted. I'm not
>> thinking the bulb is going to light very bright while testing a HV
>> diode, but should still give an indication.
>>
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Received on Sat Jul 20 23:59:12 2002