Re: [DML] Re: Electrical door lock fix + alarm? Suggestions?

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

The lock module is quite clever in that respect. As it uses relays to 
power the solenoids, as soon a the relay breaks contact the voltage goes 
crazy only in the solenoid itself. The power supply to the solenoids is 
kept seperate from the power supply to the module, and the former comes 
directly off the main 12v cluster behind the back board. They draw less 
than the colling fans on startup, also inductive devices

The problems with the lock module are threefold

1) The relays are open to the air and are underrated
2) the original system uses capacitors dumped across the relays to power 
the solenoids - this is how it only works for half a second or so. The 
snag is that a relay powered from a decaying voltage will break contact 
poorly and cause arcing and can weld themselves shut (see 1)
3) There are no protection diodes on the transistors that switch the 
capacitors across the relays, though for these to pop is quite rare.

We replace the transistors with 2n222's which are common as muck and 
much meatier, add protection diodes and replace the relays with 
hermetically sealed ones which means no oxidisation and no sticking. 
Anyone with a bit of soldering skill can do this for less than $10

Martin

Toby Peterson wrote:

>As an aside to this, perhaps some of the more experienced electrical 
>wizards on this List would like to share their thoughts regarding 
>the massive voltage and in-rush current spikes that are created by 
>the door lock solenoids, and their possible effects on other parts 
>of the electrical system?
>  
>





To address comments privately to the moderating team, please address:
moderators@xxxxxxxxxxx

For more info on the list, tech articles, cars for sale see www.dmcnews.com

To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/dmcnews/

<*> To unsubscribe from this group, send an email to:
    dmcnews-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/