Temperature gauge lineariser

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Temperature gauge lineariser

Postby GeoffSmith » Wed 30.04.2014, 01:07

Having now successfully used a PIC for my one touch window up/down control, I've subsequently designed a nifty plug-in circuit - no wire cuts, it just taps into the sender/gauge line, reads the voltage and applies some correction pulses (the duration of which are determined by a quadratic equation) to adjust the gauge reading. This corrects the incompatible temperature sender and gauge so normal operating temperature (85°C) is now at half scale and the scale markings now correspond to 45, 65, 85, 105 and 125°C. The fans now come on at around ¾ scale, just like a normal car - well they do according to the spare instrument panel I have sat on top of my pc.

As I had some spare memory (only 1kB in total :shock: ) and I/O, I have added an output interface to activate the fan relay and a pair of outputs for a bicolour LED. The unit will switch the fan on at e.g. 95°C (accompanied by a green LED) and off at e.g. 90°C. If the temperature rises above e.g. 100°C, then the LED will turn red and may even flash above e.g. 110°C to signify a potential overheating problem.

LinearTemperatureGaugeElanScan.gif

The above amended ElanScan traces should make it easier to visualise but before I do my final build and plug it in the car, has anyone got any thoughts on what the three critical temperatures should be?
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Re: Temperature gauge lineariser

Postby Fredjohn » Wed 30.04.2014, 09:41

:goodposting: :clap:


Great work Geoff: yet another mod from LEC, and one that is actually very useful instead of being "blingy"

Is it intended to replace the existing temp sensor for the fans as well as sorting out the gauge, or can it just be used for the gauge alone whilst retaining the existing sensor?

My reply to "what temp" would be to ask at what temps does the existing sensor activate/de-activate the fans? Surely it would make sense to use these values as determined by Lotus/Isuzu??

Would be interested in having one as I do not like the way the gauge reads at all. I seem to recall a posting on here somewhere about a simple mod which achieved similar results, but was perhaps less sophisticated.

Keep us all up to date!!
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Re: Temperature gauge lineariser

Postby dapinky » Wed 30.04.2014, 09:50

Oi Smiffy - where is it.......

....the list, man, the list - where is it?????

1) Geoff
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Re: Temperature gauge lineariser

Postby Rob P » Wed 30.04.2014, 09:57

I'm in for this, sounds like a really useful Mod :D

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Re: Temperature gauge lineariser

Postby Fredjohn » Wed 30.04.2014, 10:00

dapinky wrote:Oi Smiffy - where is it.......

....the list, man, the list - where is it?????


Here:

1) Geoff
2) Pinky
3) Rob P
4) Fredjohn
5)

Found the mod reference I mentioned above in WikiLEC: http://wikilec.9600.org/index.php/Coola ... ure_Sender
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Re: Temperature gauge lineariser

Postby Enright » Wed 30.04.2014, 10:12

What, no more <tap, tap> "is this thing working :? " / "OMG! :shock: "
Alright, I'm in! :-D

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Re: Temperature gauge lineariser

Postby Jeemy » Wed 30.04.2014, 11:02

Whee yes please.

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Re: Temperature gauge lineariser

Postby KevB » Wed 30.04.2014, 11:30

Me too Please!
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Re: Temperature gauge lineariser

Postby cliff » Wed 30.04.2014, 12:13

Nice one Geoff.

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Re: Temperature gauge lineariser

Postby muley » Wed 30.04.2014, 13:04

Nice one Geoff.

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Re: Temperature gauge lineariser

Postby davidcgriffiths » Wed 30.04.2014, 22:15

muley wrote:Nice one Geoff.

1. Geoff
2. Pinky
3. Rob P
4. Fredjohn
5. Enright
6. Enright
7. Jeemy
8. KevB
9. Cliff
10.Jim (muley)
11. David Griffiths


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Re: Temperature gauge lineariser

Postby rip » Wed 30.04.2014, 23:41

Nice one Geoff.

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4. Fredjohn
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6. Enright
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8. KevB
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12. rip
13.


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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 04.05.2014, 00:06

*ignores list*

My car now runs with the temperature gauge here:

Img_0032@80 x640.jpg


The fans switch on at a predetermined level (95°C) which should be about here on the gauge:

Img_0036@95 x640.jpg


The fans did not kick in and out at the correct temperatures so after a lot of head scratching, I discovered that whoever measured the sender and put the data on the Wiki (no names, no pack drill), measured the resistance with respect to the instrument panel earth - when the engine is running, there is about 11mV difference between the two earths and the resistance measurements are out by about 50 ohms which screws up the high temperature response which means I need to rehash the data. :banghead:

Also the fan relay socket is pretty impossible to get at so I've modified a relay (connected a wire to the coil terminal) and plugged that in to allow fan switching. Several years ago (I seem to remember Clemo pushing a wire in the socket and jamming the relay home) fitted a fan over-ride switch - does anyone have any tips on accessing the relay socket connections?

Another cunning thought is that I can possibly implement a run on timer to get the recirculating pump operational every time the engine is stopped - not so much to cool the engine but to stop the pump from seizing through lack of use.
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Re: Temperature gauge lineariser

Postby tigerdog » Sun 04.05.2014, 01:58

GeoffSmith wrote:Another cunning thought is that I can possibly implement a run on timer to get the recirculating pump operational every time the engine is stopped - not so much to cool the engine but to stop the pump from seizing through lack of use.


Absolutely brilliant. It will also serve to circulate coolant through the turbo even when it's not hot enough to kick the pump on normally. I think this can only help prolong turbo life.
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Re: Temperature gauge lineariser

Postby muley » Sun 04.05.2014, 09:14

Geoff,

Excellent piece of wizardry..

Cheers

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Re: Temperature gauge lineariser

Postby dapinky » Sun 04.05.2014, 14:05

GeoffSmith wrote:*ignores list*



I thought you'd bite about the list well before now....... I just assumed that you'd accepted it and locked yourself away inside the garage with a soldering iron and a lot of envelopes :lol: :lol: :lol:
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Re: Temperature gauge lineariser

Postby steve matthews » Sun 04.05.2014, 14:16

I like your progression and I am interested.
Do we have to have the rubber band thing exposed like that or can we put it away somewhere :lol:

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Re: Temperature gauge lineariser

Postby John_W » Sun 04.05.2014, 15:10

Geoff,
Brilliant idea. Can you also make up a batch of wee stickers to apply to the gauge to say "Don't panic - the temperature gauge on this car is meant to read mid scale. This Elan is fitted with a Geordie Enterprises temperature gauge lineariser". Actually, forget it - a sticker with that many words on it would obscure the entire gauge anyway.

Some words of encouragement:
GeoffSmith wrote:... Also the fan relay socket is pretty impossible to get at so I've modified a relay (connected a wire to the coil terminal) and plugged that in to allow fan switching. Several years ago (I seem to remember Clemo pushing a wire in the socket and jamming the relay home) fitted a fan over-ride switch - does anyone have any tips on accessing the relay socket connections?

A few key quotes from Clemo's original write-up (now sadly lost to the forum):
"Under the main dashboard cover lie two banks of relays. The top row of relays has 4 along the top (with aircon) or 3 without. The one on the right of that bank is the fans relay. Pick up leg 85 from that relay and take it to a switch (previously taken from a Vauxhall Carlton) fitted under where your digital clock is, then run a wire back up to the right hand bank of fuses with a large phillips headed screw (its the only obvious one) this is earthed ."
"... you need to take out the relay and locate leg 85. It is clearly marked on the back of the relay. Wrap a wire around this leg so that when you put it back in, it will make a connection. Drop the wire to wherever you are putting the switch."
"The circuit only works with the ignition ON with or without the engine running but NOT with the keys out. DO NOT try and get the back lights (in the switch) to work; it will cause problems with the ECU."
"I found this very easy to fit. It is crude in its fitting. I did try every other way of getting into the underside of the relays to pick up a wire but it is impossible to get to it without major dashboard removal."
I think the last quote is the one most apposite to your request for tips on accessing the relay socket connections.

GeoffSmith wrote:... Another cunning thought is that I can possibly implement a run on timer to get the recirculating pump operational every time the engine is stopped - not so much to cool the engine but to stop the pump from seizing through lack of use.

Brilliant idea.

The attached graph shows where the fans kick in on my car, so I vote for you to try to keep the same temperature thresholds in your modified set-up.

Good work,
John

PS: I disagree with Steve - I like the rubber band thing.
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Re: Temperature gauge lineariser

Postby Elanlover » Sun 04.05.2014, 19:48

Geoff, just for us laymen (which might only be me as it seems everyone else gets it) what precisely will this gadget do relative to the normal operation of the car?

In my car the "normal" (while driving) temp seems to stabilize at about the halfway mark. If I come to a stop it doesn't take long for the gauge to rise to the 3/4 mark and the fans kick in just above that mark (the needle likely reads a little bit higher after I pulled it off to replace the dial faces). Now, some time ago I purchased a lower temp thermostat and lower temp sender that was supposed to open the thermostat at a lower temp and start the fans earlier. I believe this was a Rodney Dickman mod that was available a while ago. I've yet to install it however.

So, are you saying that what you're working on will accomplish something similar? "Similar" in that the fans will come on sooner and keep the car running slightly cooler (obviously the thermostat won't be affected)? Thanks!
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 04.05.2014, 23:33

John_W wrote:Geoff,
Brilliant idea. Can you also make up a batch of wee stickers to apply to the gauge to say "Don't panic - the temperature gauge on this car is meant to read mid scale. This Elan is fitted with a Geordie Enterprises temperature gauge lineariser". Actually, forget it - a sticker with that many words on it would obscure the entire gauge anyway.


Fortunately I will only need to make one. :-D

John_W wrote:A few key quotes from Clemo's original write-up (now sadly lost to the forum):
"Under the main dashboard cover lie two banks of relays. The top row of relays has 4 along the top (with aircon) or 3 without. The one on the right of that bank is the fans relay. Pick up leg 85 from that relay and take it to a switch (previously taken from a Vauxhall Carlton) fitted under where your digital clock is, then run a wire back up to the right hand bank of fuses with a large phillips headed screw (its the only obvious one) this is earthed ."
"... you need to take out the relay and locate leg 85. It is clearly marked on the back of the relay. Wrap a wire around this leg so that when you put it back in, it will make a connection. Drop the wire to wherever you are putting the switch."
"The circuit only works with the ignition ON with or without the engine running but NOT with the keys out. DO NOT try and get the back lights (in the switch) to work; it will cause problems with the ECU."
"I found this very easy to fit. It is crude in its fitting. I did try every other way of getting into the underside of the relays to pick up a wire but it is impossible to get to it without major dashboard removal."
I think the last quote is the one most apposite to your request for tips on accessing the relay socket connections.


Thanks for that John, that's pretty much how I remembered it. I would like to think that drilling a hole in the relay pin and soldering the wire to it is slightly more elegant though.

John_W wrote:The attached graph shows where the fans kick in on my car, so I vote for you to try to keep the same temperature thresholds in your modified set-up.


Although (psychologically) the gauge response will appear be slightly less worrying because it will start from 50% rather than 20%, I think I would prefer to cycle the fans at under 100°C (at under ¾ scale and accompanied by the green indicator) and to light/flash the red warning light if it gets over ¾ scale and close to the fan switch having to come into operation.

John_W wrote:PS: I disagree with Steve - I like the rubber band thing.


Good man.

Elanlover wrote:In my car the "normal" (while driving) temp seems to stabilize at about the halfway mark.


Blair, you do have an Elan don't you? :smt017 The eternal problem has been that the gauge and sender are not matched so normal running is a needle width under the ¼ mark which makes it difficult to see when e.g. the thermostat sticks open because the gauge only drops to two needle widths below ¼.

Look at the ElanScan plots above and you can see that the thermostat keeps the temperature at ~80-85°C. In the absence of sufficient airflow, the temperature climbs to ~110°C where the fans kick in and drop the temperature to ~100°C. My plan is to activate the fans at ~95°C to keep the maximum temperature cycling around 90-95°C similar to the Dickman low temperature switch. Note if my box fails to operate correctly or if it is removed, the fan switch will still operate at 110°C.
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