Temperature gauge lineariser

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Re: Temperature gauge lineariser

Postby maz_r » Fri 26.06.2015, 12:33

Saltire wrote:Or at least the circus diagram and parts list so I can DIY :-D


As requested
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Re: Temperature gauge lineariser

Postby Fredjohn » Fri 26.06.2015, 12:34

lotusflasherman wrote:Geoff, I agree in principle, but ... I've downloaded Elanscan software but haven't yet sourced a plug so it's not 'easier to plug in Elanscan' for me, yet. (It's on my 'things to do' list.) Got any spare USB's leads? :bowdown:


These are sourced from Geoff (see his signature) for a reasonable sum, given that the software is free. (Geoff I'll take my commission once sold!!!!)

My gauge also acts exactly as yours Ian, and the stat opens accordingly having done an Elanscan, but I'd still be more comfortable with a gauge that reflects more accurately what is happening. No pressure Geoff.........
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Re: Temperature gauge lineariser

Postby GeoffSmith » Fri 26.06.2015, 20:21

maz_r wrote:
Saltire wrote:Or at least the circus diagram and parts list so I can DIY :-D


As requested

You forgot the parts list Martin. :roll:
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Re: Temperature gauge lineariser

Postby Saltire » Fri 26.06.2015, 21:21

maz_r wrote:
Saltire wrote:Or at least the circus diagram and parts list so I can DIY :-D


As requested

Now that would save me a lot of cash on building a garage - I reckon I could get 20 M100s in there :D
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sat 27.06.2015, 20:11

I give in! Too many people have hassled me (in the nicest possible way) so the situation is this:

I ended up using a PIC to a) measure the voltage on the gauge and b) drive a MOSFET to force some extra current into the gauge to linearise it. The clever bit was working out a simple algorithm that could be programmed into the PIC but it is almost perfect now. Unfortunately I used a tool called Flowcode to develop the code but my evaluation license has expired and I haven't found time to either load a new install and try for another trial or to reverse engineer the code. All I know is it works well on my car and apart from a minor modification to the mark-space ratio at normal running temperature and dropping the fan threshold (for purely psychological reasons) I'm happy with it.

The plan was to get some pcbs made up and to get my son to build them up and program the PICs to supplement his grant. (Un)fortunately, retirement, LOG35 and buying a villa in Spain have taken precedence, but maybe towards the end of the year I will get this resurrected. After all, I will need something to do in November when I'm sat in the hot tub.....

PS I could post a circuit diagram but without the updated PIC code, it's not a lot of use!

PPS I may modify it slightly to add a run-on timer to exercise the recirculating pump.

PPPS I have two USB interfaces left but we're off to Spain on Wednesday.
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Re: Temperature gauge lineariser

Postby Saltire » Sat 27.06.2015, 21:09

GeoffSmith wrote:PPPS I have two USB interfaces left but we're off to Spain on Wednesday.


I'll take one please - email on the way.
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sat 27.06.2015, 21:35

PPPPS I have one USB interface left but we're off to Spain on Wednesday.

PPPPPS Anyone want any stainless headlight springs while I'm rummaging around in the loft and playing Postman Pat?

PPPPPPS Anyone want any Wilwood nipple caps......
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Re: Temperature gauge lineariser

Postby Saltire » Sat 27.06.2015, 23:00

OK then, twist my arm, I'll have some headlight springs as well please. I know the silvering's going on two, and it will prompt me do get down to it. [Note to self: must do some research on recommended headlamps. Shame Cibie don't exist any more]
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Re: Temperature gauge lineariser

Postby Fredjohn » Sun 28.06.2015, 07:54

GeoffSmith wrote:PPPPS I have one USB interface left but we're off to Spain on Wednesday.

PPPPPS Anyone want any stainless headlight springs while I'm rummaging around in the loft and playing Postman Pat?

PPPPPPS Anyone want any Wilwood nipple caps......


Yes please Geoff... My (Wilwood) nipples need covering. Put me down for a set.
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Re: Temperature gauge lineariser

Postby Ian T » Sun 28.06.2015, 09:29

GeoffSmith wrote:I ended up using a PIC to a) measure the voltage on the gauge and b) drive a MOSFET to force some extra current into the gauge to linearise it. The clever bit was working out a simple algorithm that could be programmed into the PIC but it is almost perfect now. Unfortunately I used a tool called Flowcode to develop the code but my evaluation license has expired and I haven't found time to either load a new install and try for another trial or to reverse engineer the code. All I know is it works well on my car and apart from a minor modification to the mark-space ratio at normal running temperature and dropping the fan threshold (for purely psychological reasons) I'm happy with it.

PS I could post a circuit diagram but without the updated PIC code, it's not a lot of use!


I have about as much time as you do perhaps (when not under the car that is) but I used to be really into PIC programming and depending on how you did it (PWM charge pump, or D>A?) I might be able to knock something together.
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Re: Temperature gauge lineariser

Postby Ian T » Sun 28.06.2015, 09:37

How time has moved on... just looked at Flowcode and the cheap £79 'PIC' licence looks like good value, apart from the fact that it excludes wired communications (I'm expecting SPI and USB in that). :(

I still have all the MPLAB stuff, with ICD2 and ICD3 as well as (ahem) PROmate and it's accompanying in-circuit emulator for PIC17C42 and 16C64, which were what I learned on.

Surely someone else still thinks that assembly language is beautiful? ;)
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 28.06.2015, 10:53

Saltire and I for two. I cut my teeth on the 8085 and CD is CALL, DB is IN, C3 is JMP, C9 is RET....
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Re: Temperature gauge lineariser

Postby Ian T » Sun 28.06.2015, 11:07

GeoffSmith wrote:Saltire and I for two. I cut my teeth on the 8085 and CD is CALL, DB is IN, C3 is JMP, C9 is RET....


LOL. I had it easy - I learned 8085 also, but using mnemonics and compiler. We did have to hand assemble also, plus in my grant funded days of education, had to find faults in assembled hex codes from a functional description.

Some of my work colleagues now programming PICs in C or basic, no idea of what is happening inside and always running out of space!
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 28.06.2015, 11:10

Same with Flowcode. I just paid an extra 2p and bought the next spec. part up the list.
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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 28.06.2015, 12:20

I just paid an extra 2p and bought the next spec. part up the list.

That bit is in an infinite loop obviously - how else did the pc evolve?
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Re: Temperature gauge lineariser

Postby Ian T » Sun 28.06.2015, 12:31

GeoffSmith wrote:
I just paid an extra 2p and bought the next spec. part up the list.

That bit is in an infinite loop obviously - how else did the pc evolve?


Dunno... I just paid the extra 2p and bought the next spec part up in the range... ;)

I've never had a PIC programming that did something and then 'permanently finished' functioning. They all have infinite loops as you well know it takes quite a lot more effort to sneak past the compiler so it executes all the NOPs. Suppose you could put it into low power sleep mode with no wakeup.
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Re: Temperature gauge lineariser

Postby Elanlover » Sun 28.06.2015, 13:38

Why don't you two get a room..................


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Re: Temperature gauge lineariser

Postby GeoffSmith » Sun 28.06.2015, 14:00

We're trying to get a life first..... :smt098
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Re: Temperature gauge lineariser

Postby Saltire » Sun 28.06.2015, 19:59

GeoffSmith wrote:Saltire and I for two. I cut my teeth on the 8085 and CD is CALL, DB is IN, C3 is JMP, C9 is RET....


The bit I liked most was getting the 100-page dump printout, finding the one card which had been punched incorrectly, re punching it, refiling it in the box of cards, and then tripping over a stray cable on th way into the machine room and dropping the lot. I learned to number the cards after that.

A room for three, perhaps :gathering:
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Re: Temperature gauge lineariser

Postby GeoffSmith » Thu 09.07.2015, 22:57

Good news. I came across my second prototype board (which I'd forgotten about but which is nearly full populated) and I've found and managed to program up another PIC.
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