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Old 27th January 2009, 06:52   #21
stevemac
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Quote:
Originally Posted by hans.schaaper View Post
Thanks everyone for your positive and enthusiastic response.
I am working on a solution to offer this gadget to forum members at the most reasonable cost I possibly can.
I am designing printed circuit boards to be manufactured by professional third party.
I will aim at 40pcs wanted total and base the cost on that.
Suggestions for further enhancements are welcomed.
An audible alarm but at what temperature?

Will keep you posted.

Hans
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I am happy to lose one of my cupholders for that! The drivers side is pretty useless anyway.
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Old 27th January 2009, 10:41   #22
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brilliant-you can put me down for one when they start rolling out!

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Old 27th January 2009, 11:24   #23
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I'd be interested in this gizmo in kit form. I think if you could get all the bits and pieces with an instruction leaflet it would make the installation much more interesting. I'm sure there are lots of people with a DIY bent who would love a little project like this.

TC
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Old 27th January 2009, 12:19   #24
StevenWilliams
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when you know more please keep us updated. I would definutly be interested in buying a kit.
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Old 27th January 2009, 12:23   #25
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Yep looks excellent, keep us posted!

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Old 28th January 2009, 14:06   #26
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Wouldn't mind one myself! As T-Cut says, a kit form one would do just as well for us techie wannabes!
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Old 28th January 2009, 23:03   #27
hans.schaaper
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Some clarification.
When I said "I am designing printed circuit boards to be manufactured by professional third party." I meant the circuit boards only.
The components still need to be soldered on.
So if you prefer to do this yourself this is certainly an option.

An audible alarm will affect the the board size and the cost.
Plus the issue of the set point which will be fixed and as a consequence must be chosen rather conservative to avoid going off on a warm day in summer traffic.
Please advise.

Hans
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Old 28th January 2009, 23:39   #28
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How about one with a blue backlit display for the ZT boys ?
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Old 28th January 2009, 23:43   #29
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Quote:
Originally Posted by hans.schaaper View Post
An audible alarm will affect the the board size and the cost.
Plus the issue of the set point which will be fixed and as a consequence must be chosen rather conservative to avoid going off on a warm day in summer traffic. Please advise.
Regarding an alarm set point. It would seem logical to me to have this at the temperature reached when the pressure relief valve is about to open. This is the most common mechanism by which coolant is lost. After that stage, more serious events could follow if the coolant isn't replaced, so a warning at that point would seem best. If the coolant level was already low, but an overheat hasn't occured, then the same criterion would apply. It will still blow at the same temperature.

The pressure required to open the relief valve is known. I think we have to assume all caps are rated at 140 mPa (1.4 bar approx). It's easy enough to find the temperature at which the vapour pressure is 1.4 bar, again with an assumption thrown in. This is that the coolant is simply water. The presence of 50% ethylene glycol will depress the vapour pressure somewhat, but the calculation should give a 'safe side' value.

Looking at a pressure/temperature curve (for example: http://en.wikipedia.org/wiki/File:Wa...sure_graph.jpg), it appears to be around 112-115C. This temperature also seems to correspond to the start of the emergency cooling fan band, when the highest fan speed available is tripped.

TC

Last edited by T-Cut; 28th January 2009 at 23:47..
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Old 29th January 2009, 19:44   #30
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Good thread & many Thanks for your research Hans!

I wonder now with your knowledge of the I-bus interfacing etc, whether the standard Temperature gauge could be somehow re engineered to be made a darn site more accurate! ...Like reading Zero deg C in the blue, & say 120 deg C in the red Zone as you would expect!

Maybe the above might suit the purists who don't lose the use of their cup holder or want to drill extra holes, making their car non-standard etc.
And whilst the IPK was in pieces calibrating the Standard Gauge, maybe a Audible alarm could be added there too.

Worth mentioning that the I-bus relies on data from various sensors round the car, & is assuming that these sensors are "in spec" & giving the correct readings.
I've replaced a few R75 water temp thermistors that tend to "read low" as they age.


Just pondering & keep up the good work
Jules
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