The banner above is an advertisment - if it asks you to download software, please ignore.
Site News - 7/1: Members: Log In to See Fewer Ads! | 5/28: SAAB Evolutions/TSN T-Shirts $14
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

9000 Bulletin Board
1985-1998 [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main 9000 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Relays - Bosch 5006 vs. 5013
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Brian Catt [Email] (more from Brian Catt) on Fri, 19 Jun 2009 06:59:46 Share Post by Email
In Reply to: Relays - Bosch 5006 vs. 5013, 92Scarab, Sun, 17 Jun 2007 19:12:00
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

I know what diodes on relays are for, used to be a design engineer, am MIEE.

They are normally to protect the transistor driver from the reverse voltage spike which is created when the relay breaks, so if correct the diode will be across the energising coil, not the switched power contacts.

When you power and unpower a relay it generates a voltage as the cuurent is changed from on to zero, the opposite of what is gnerated that opposes thie latching current when its energised, its EMF is proportional to the rate of change of current, di/dt

Its a diode it is set so it carries no curent when the voltage is normal polarity, but will short circuit any opposite polarity voltage to the driver stage. Solid state drivers can be damaged by a reverse voltage on their collectors (for techies the collector base junction becomes forwad biased and may carry serious current, bad for the base connection which has a low max current.

It may that later driver circuits had their own output protection, or this was a Bosch thing in case the car maker's driver electronics didn't protect itself and one never needed the Bosch diode in the first place. They fit a lot of cars so I guess it isn't needed, but its a hard way to find out if it is.... feeling lucky?

Hope this helps, a bit.

Brian Catt 01932 772731

posted by 78.151.243...

Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2024 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]

Random Saabnet.com Member Gallery Photos (Click Image)
This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot


Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!