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Using Arduino => General Electronics => Topic started by: ilioSS on Nov 13, 2012, 08:07 pm

Title: Equivalent 1N918
Post by: ilioSS on Nov 13, 2012, 08:07 pm
Hello,

I am working on a ultrasonic windmeter.
In the schematic a 1N918 diode is used.
This one is not available local.
The internet gives as equivalent the 1N914 the same story not available.

It is a UHF type diode.
What is the best diode to use?

Hope to get a awnser,

Theo
Title: Re: Equivalent 1N918
Post by: oric_dan on Nov 13, 2012, 08:28 pm
Just your basic silicon signal diode, equiv 1N4148.

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_36311_-1

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_36038_-1

Without seeing the schematic, the bet is that ultrasonic windmeter is not using a UHF diode.

Title: Re: Equivalent 1N918
Post by: dhenry on Nov 13, 2012, 08:52 pm
It will depend on how the diode is used. Generally 1n4148 is a good replacement for it but may not if the diode is used in an application for its unique characteristics.
Title: Re: Equivalent 1N918
Post by: retrolefty on Nov 13, 2012, 09:07 pm
I would suspect any silicon diode would work, even a 1N4001 type power diode. There is no need for microwave speed in a wind speed circuit. But link to a schematic if you want 100% for sure correct answer under all conditions.  ;)

Lefty
Title: Re: Equivalent 1N918
Post by: oric_dan on Nov 13, 2012, 09:40 pm
What on earth does 'unique' even mean?
Title: Re: Equivalent 1N918
Post by: Docedison on Nov 14, 2012, 03:07 am
You couldn't tell the difference between a '918 and a '4148... the 4148 I think has a higher forward current capacity and the '918 has a few uA less reverse leakage as well as a slightly higher switching speed but the differences are small, Use the 1N4148 as the 1N9XX diodes are really no longer even Mfd'd. I've attached data sheets for both in case you are curious.

Bob

Title: Re: Equivalent 1N918
Post by: westfw on Nov 14, 2012, 06:12 am
Quote
What on earth does 'unique' even mean?

Every once in a while, someone will put a device in a circuit in such a way that "unique" characteristics not captured on the spec sheet, or subject to a wider range of tolerances than you would expect, will play a large role in the performance of the device.  I've seen this most often in "sound synthesizer" type circuits (Like the Adafruit X0XB0X, where builder's go out of their way to find things like "matched pairs of ORIGINAL <manufacturer> XXYYZZ transistors", because it turns out that when you put something else in there, it ends up sounding different.
Title: Re: Equivalent 1N918
Post by: MarkT on Nov 14, 2012, 07:47 pm

I would suspect any silicon diode would work, even a 1N4001 type power diode. There is no need for microwave speed in a wind speed circuit. But link to a schematic if you want 100% for sure correct answer under all conditions.  ;)

Lefty



1N4001s are very very different to 1N4148, perhaps 100 times slower to switch (1N4148 is 4ns) - but the main reason to avoid a 1N4001 is that the leads may be too thick to fit the holes!!

If you don't have 1N4148's in stock, start by buying a few dozen as they are cheap and v. handy.
Title: Re: Equivalent 1N918
Post by: retrolefty on Nov 14, 2012, 07:57 pm


I would suspect any silicon diode would work, even a 1N4001 type power diode. There is no need for microwave speed in a wind speed circuit. But link to a schematic if you want 100% for sure correct answer under all conditions.  ;)

Lefty



1N4001s are very very different to 1N4148, perhaps 100 times slower to switch (1N4148 is 4ns) - but the main reason to avoid a 1N4001 is that the leads may be too thick to fit the holes!!

If you don't have 1N4148's in stock, start by buying a few dozen as they are cheap and v. handy.


My point was that without seeing the specific application/schematic the diode is being used in, it's very possible any old silicon diode would work. Or do you have more specific information? The OP was obviously working off some parts list so it's reasonable to ask that he has access to the schematic. And as I said it's very possible some random silicon diode he might already own would work just fine. Yes I know a 1N4001 is not identical to a 1N4148, and I didn't imply as such.

Lefty
Title: Re: Equivalent 1N918
Post by: ilioSS on Nov 17, 2012, 12:45 pm
Hello,

I enclosed the description of the windmeter.
Hope you can open the file.

This will explaine the use of the diode.

Theo
Title: Re: Equivalent 1N918
Post by: MarkT on Nov 17, 2012, 01:15 pm
Its used as a small signal rectifier in the envelope detector so any small signal diode will do.  Given its only 40kHz and low current then pretty much any small diode would work I think.  You could even try a red LED!!
Title: Re: Equivalent 1N918
Post by: ilioSS on Nov 17, 2012, 01:31 pm
Hello,

MarkT,

Thanks for the responce.
I was afraid this is a very difficult to get diode. As on internet is is difficult for a data sheet.
An equivalent 1N914 is the same story.
So I will fit a small signal diode and see what wil happen.

Thanks,

Theo
Title: Re: Equivalent 1N918
Post by: oric_dan on Nov 17, 2012, 07:01 pm
Quote
Its used as a small signal rectifier in the envelope detector so any small signal diode will do. 


Yeah.