Re: [doc] Door Lock Module - some technical musings...

["Paul Salsbury" <paul.salsbury@xxxx>]

Thanks
Martin, After reading that through 3 time I think it has sunk in..... Thanks
for helping me with that one I owe you one now.

Cheers

Paul


----- Original Message -----
From: "Martin Gutkowski" <webmaster@xxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>; <doc-uk@xxxxxxxxxxxxxxx>
Sent: Friday, December 28, 2001 10:35 PM
Subject: [doc] Door Lock Module - some technical musings...


> Hi All,
>
> I've spent some of my quiet time this Christmas looking at the DeLorean
> door lock module. Having spent time previously examining Dave Swingle's
> pain-stakingly documented layout diagram and circuit diagram on the
> DMCnews tech page, I've discovered some things and re-engineered two
> modules already for reliability and longevity (for at least the next 20
> years :-)
>
> This was prompted by Paul Salsbury complaining that his didn't work at
> all, and sending it to me to fix.
>
> Firstly, referring to the circuit diagram here
>
> http://www.dmcnews.com/Techsection/graphics/lockcircR1.jpg
>
> some errors:
>
> 1) Transistors Q1 and Q11 are in fact BFR39 and NOT BRF39 as stated.
> BFR39's are pretty common and still available. I got ten on sample from
> www.diamondelec.co.uk
>
> 2) R1 and R11 are in fact in series between D2 and the emitter of Q1
> (and likewise between D12 and the emitter of Q11). C1 and C11 connect
> directly between ground and Q1 and Q11's emitters respectively.
>
> What do we know about the module and it's problems?
>
> 1) The relays can stick shut energising the solenoid until it burns out
> or the curcuit breaker trips (if present) or the battery flattenns.
>
> 2) Referring to Nathan's notes on the module, the transistors are
> vulnerable to spikey voltages resulting from intermittent earthing
> during the lock or unlock cycle. He also notes that he'd put a diode in
> series between point A and output pin 2.
>
> 1: The original relays are open to the air and have a pathetically small
> contactor. This is a recipie for sparking casing gumming up of the
> contacts. Regular cleaning with a switch lubricant like servisol10 is
> likely to prevent the contacts sticking, though it's an underrated
> device. (A small fact which may be of interested to some is that the
> explosion aboard Apollo13 was traced back to the use of an underrated
> relay getting stuck closed - you have to read the book to get the
> detail!). I found a nice 10A miniature relay made by Siemens available
> from Maplin for £1.49. It's almost the exact same size as the stock
> relays.
>
> 2: When I tested Paul's module, I discovered that one "side" of the
> circuit was functioning correctly, but the other was failing to charge
> its capacitor (the one that energises the relay). The likely culprit was
> the transistor Q1 so I replaced it (I also replaced the two capacitors
> on principle. On re-trying the module, I found no change. This was a
> puzzle because there's not a helluva lot else on the board that can go
> wrong! Remember this board is actually two identical circuits in
> parallel - one performs the "lock" function, the other the "un-lock"
> function. Paul's would unlock but not lock. It was after a lot of
> head-scratching that I noticed something strange... D5 has no "partner"
> on the "lock" side of the circuit. Even stranger, my own working module
> had D5 mounted by hand to the underside of the board, with the track
> cut. Pauls was evidently a later board with a position for D5. NEITHER
> board had a place for the same diode on the lock circuit. The lock relay
> on Paul's board was sparking badly when manually closed it, so I
> concluded that Q1 was being blown due to a spike on the base. I cut the
> track from pin 2 to point A and added in a diode (marked "D" on the
> diagram). I also added the protection diodes from point A and B to the
> 12v supply. Hey presto the module works fine, with a lovely blue flash
> ever time the lock relay is triggered. So I removed the stock relays and
> replaced them with the Siemens ones. It required some creative
> additional wiring, but you can use the holes for the original relays to
> feed to the underside of the board. It's very easy to solder direct to
> the tracks on the underside as it was never coated.
>
>
>
>
>
>
>
> DOC UK Website: www.delorean.co.uk
> Unsubscribe: doc-uk-unsubscribe@xxxxxxxxxxx
> ** Unless otherwise stated, all messages posted to the group are assumed
public and may be printed in the club magazine **
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>