# Can you identify this diode?

Discussion in 'Automotive Electronics' started by Pingu, May 31, 2016.

1. ### Pingu Thread Starter New Member

May 31, 2016
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I thought about putting this post in the Automotive section, but thought that it is more of a project question than an automotive question.

My car has variable valve timing that is controlled via four solenoids. Each of the solenoids is protected by a diode. The diode is inside the solid plastic body of a plug connector. The plug is at the front of the engine, in the airflow from the radiator, so may be subject to temperatures around 80-100 deg C.

When I was stripping the plastic connector apart in order to find an open circuit, I damaged one of the diodes. The good diode has no part numbers or markings of any kind on it.

Here is an image of the plug post-Dremelling...

I've been able to measure the approximate forward voltage as 460V...

I'm a mechanical engineer by education and did electrical engineering as part of my degree, but it has taken me several days of Googling to find out that it's a rectifier diode and it looks remarkably like a Vishay BW-type, but there are lots to choose from (and none are 3.6mm dia spheres)...

http://www.vishay.com/product?docid=86049
http://www.vishay.com/docs/49301/49301.pdf

http://www.vishay.com/docs/86100/fundamentals.pdf
I've read the attachment above and I'm confused by "reverse recovery characteristic". I understand what it means, but I don't know how I can reverse engineer it in order to decide the correct diode.

I hope that the short video that I've made shows enough information about the solenoid for someone who knows what they are doing to be able to decide on the correct diode...

Any help is much appreciated
Cheers, Gary

Jul 18, 2013
10,836
2,510
If these are reverse emf diodes, then 1n4007 should work.
Forward voltage would be around .461v
Max.

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3. ### Pingu Thread Starter New Member

May 31, 2016
6
0
Thanks for helping.

I did think that something from the 1N4000 range would do the job, but my concern is why would the original designers have specced such an exotic diode? Could it be something to do with the environment (hot engine bay)?

I read on another site that the forward voltage to protect against is approx 4x Voltage and 10x current, so I ordered a pack of 1N5408s (approx \$2). I know that 1N5408 is vastly over-specced for what I think the diode is for, but better safe than sorry .

Gary

4. ### #12 Expert

Nov 30, 2010
16,671
7,315
@Pingu

1KV, 3A continuous
IFsMax = 200A

That 461 reading is millivolts of forward voltage drop of the diode at 1 milliamp of current, not the rating of the survivable diode voltage.
Trr (Time, reverse recovery) is not important to you. It describes how fast the diode can turn off after the current has stopped. You can't buy a diode that is too slow. The worst diodes take less than a microsecond to recover and no car engine goes anywhere near 1 million RPM.
Ifsm (Amps, forward surge max) is that current which the diode must survive for a few milliseconds and will never be more than the current through the solenoid. I would be surprised to find a 50 amp solenoid in a car.

I just looked at the video. About 3 to 4 amps is your necessary Ifsm.
Voltage rating in an automotive circuit must be at least 60 volts. I prefer a 100 volt rating just because it has a safety factor of 67%.
If you want 4X voltage and 10X current, you would choose 60 volts and 40 amps of Ifsm.
That means 1N4002 to 1N4007 would work (as Max said), and they cost about 16 cents.
http://www.mouser.com/_/?Keyword=1N4007

(In 1970, we called these, "green dot diodes".)

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5. ### Pingu Thread Starter New Member

May 31, 2016
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Thanks for the help. If this were just a normal silicon diode I would use one of the 1N4000 range, but it has the dimensions of a SOD-57. Checking the specs that you have given me, I'm pretty sure that a BYW32 would do the job.

Do you agree?

http://www.vishay.com/docs/86048/byw32.pdf

Gary

6. ### ian field Distinguished Member

Oct 27, 2012
4,447
791
From experience using the DMM diode function; I've noticed that faster diodes tend to read slightly lower Vf. Basic recovery silicon usually comes in about 0.65V max - only Zeners reach the mythical 0.7V.

Its almost certainly a glass passivated rectifier, Philips and GI do ranges of this type - there's numerous Asian manufacturers and no numbers on them point in that direction.

Apr 5, 2008
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Hello,

As Ian said, philips has some of these glass bead diodes.
The BYV28 is one of them.

Bertus

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8. ### Pingu Thread Starter New Member

May 31, 2016
6
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According to the datasheet, the BYV28 is a SOD-64, which is physically bigger. 4.3mm dia ball compared to 3.6mm and a wire dia of 1.35mm compared to 0.82mm. The diode I have is 3.6mm dia with a wire dia of approx 0.82mm, so I'm pretty confident that it is SOD-57.

I'm very grateful for all the assistance and I think I am getting closer to a solution

Firstly, does anyone think that BYW32 wouldn't do the job? If not, why not? Please remember that I'm not an electrical engineer, just an avid reader of Google for the past 10 days .

Secondly, could anyone suggest a better match?

Cheers, Gary

9. ### #12 Expert

Nov 30, 2010
16,671
7,315
The byw32 datasheet says: 200v. 50A.
That is more than 60v, 40 amps.
Therefore, it is more than enough, and, "enough" is all you need.

Relax. This is one of the least critical jobs for a diode. There are lots of diodes that will do this job.
You have enough big. You have enough volts. You have enough amps. You have enough speed.
The minimum you need is 60 volts, 4 amps of Ifsm.
Somebody on the Internet said 60V 40A
Even a reliability nut like me would settle for 100 volts 10 amps.
You bought 1000V, 200 A.

Most of what I was doing in post #4 was education, not criticism.

10. ### Pingu Thread Starter New Member

May 31, 2016
6
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I'm happy to part with a few dollars now to buy some BYW32s

Thanks very much for all your help everybody.

If anyone thinks I'm wrong, don't be afraid to tell me. At a few cents a pop, I'm happy to make as many false purchases as needed to get the right part .

11. ### #12 Expert

Nov 30, 2010
16,671
7,315
It's not going to happen.
You're going way over, "enough".
The only thing that could be wrong with that is whether it fits inside the container.

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12. ### Pingu Thread Starter New Member

May 31, 2016
6
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Physically it's the same size as the original, so happy days