Re: [DML] Fan Fail Light Without Actual Fan Fail
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Re: [DML] Fan Fail Light Without Actual Fan Fail



Well, seeing as the subject came up :-)

The problem with all the systems described EXCEPT the Fanzilla (to my knowledge - I have never seen one much less taken it apart) is that the fain fail light can only tell you when the voltage is going to the fans, or when the fans should be on, or when there's an imbalance between the fans. None of these solutions actually "know" when a fan is or is not drawing current when it should. The only way to do this efficiently is with a hall effect sensor - the original fan fail module did it this way, but only comparing one fan to the other, and it was appallingly made.

I have been asked about the progress of my little project to make a fan sequencer and restore the fan-fail light functionality. I've been really busy the past month - 2 weeks filming a TV show in Glasgow (nothing to do with DeLoreans), and two joyful weeks of good weather with my DeLorean parked outside, so every evening was spent working on it, and not sweating over a hot soldering iron! However, as members of the dmc_electrics list know, I did produce a design. I found some truly fantastic IC's made by Philips which are BUK202-50X 20A high-side switches with status pin. They make it possible to build a completely solid-state fan sequencer from fewer than 20 components, which gives a genuine "fan fail" signal. Here's the design

http://www.delorean.co.uk/electronics/fandelay2.jpg

A drives the fan, B drives the fan-fail light. Two of these circuits need to be built, one per fan. R3 sets the delay. For those who are comfortable with data sheets, I've put it here

http://www.cix.co.uk/~mgutkowski/20A_switch.pdf

The BUK203 is exactly the same, but will only drive 4A and is cheaper, so ideal for the fan fail light. This device has open and short circuit detection, overheat protection (negating the need for a fuse) and under all these failure conditions, will light the fan-fail light.

NB I have NOT tested this yet, but as the subject came up.... :-)

Martin
#1458

DMC Joe wrote:

You said :
".........Also why not run one additional accessory relay so the
light only indicates a "fail" condition when there really is no voltage
going to one of the fans?.."

There is a device that does all of the above and more; it's called
"Fanzilla"!

DMC Joe
Tech Information, DMC Joe Help Club, & Store








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