Driving a temp gauge from aux 1

This section is dedicated to discussion of DTA engine control units such as the DTA E48 EXP, P8 Pro, DTA S40, S60, S80, and S100, as well as all things ECU related.
Post Reply
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Driving a temp gauge from aux 1

Post by Rob Stevens »

Hi, I have an S1 Elise that has a digital water temp gauge run from it's own sensor, this sensor is very inaccurate and unreliable, probably because it has a single pin connector? I am trying to drive this display from aux1 via pwm at 400hz, this works but the display wanders up and down about 8degC, I suspect I need a capacitor to smooth the pwm signal, but should this be to ground or 12/5v and what size capacitor?
Any pointers please.
Thanks
Alex DTA
Posts: 1622
Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79

Re: Driving a temp gauge from aux 1

Post by Alex DTA »

What is the input to the dash? Just a digital PWM?
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Driving a temp gauge from aux 1

Post by stevieturbo »

I doubt whether single or two pins would matter.

I run hayabusa clocks in my car, and annoyingly the temp sensor is connected to the ecu, and the ecu then talks to the dash ( K line or something maybe ? single wire ) and operates the gauge.

I used a Volvo temp sensor ( regular Bosch NTC but it uses only a single wire ) and it's fine.

Weird having to have a complete Hayabusa engine ecu in the car, just to operate the dash temperature gauge LOL.

Maybe the sensor is just faulty ? Many older cars just used a single wire temp sensor anyway for the gauge.
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Driving a temp gauge from aux 1

Post by Rob Stevens »

The existing sensor is something special to the stack/rover setup, its just an NTC with a 2 pin mini timer but using just one pin. unreliable and poor calibration, hence my plan to implement a D/A Converter idea that sort of works, the ECU has it's own temp sensor,
So will a capacitor help?
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Driving a temp gauge from aux 1

Post by stevieturbo »

Rob Stevens wrote: Wed Aug 17, 2022 12:46 pm The existing sensor is something special to the stack/rover setup, its just an NTC with a 2 pin mini timer but using just one pin. unreliable and poor calibration, hence my plan to implement a D/A Converter idea that sort of works, the ECU has it's own temp sensor,
So will a capacitor help?
The one off my Volvo ( only reason I used that sensor was I had one lying about ), is a two pin Bosch NTC mini timer too, but oddly the two pins are for different things.

One was for the cluster gauge, the other the ecu I think. They must have had different scalings or something. Seemed odd, but I tried it on my Granada for the Busa ecu/clocks and it worked great lol. It's been there ever since.

Have you scoped the gauge signal to see what it is actually getting at present ?
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Driving a temp gauge from aux 1

Post by Rob Stevens »

No point, I just want to implement a pwm output that mimics an NTC sensor, I am asking for suggestions on a size capacitor to smooth the output and should it be to ground or 12/5v it is working without the capacitor but the reading on the dash goes up and down which I suspect is because it needs smoothing. The calibration for bosch / lucus sensors is way off what I need and the only supposedly compatible stack/rover sensors last about 6 months until going faulty so I am fed up with buying them. I want the dash to read the same as the ecu.
Alex DTA
Posts: 1622
Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79

Re: Driving a temp gauge from aux 1

Post by Alex DTA »

If you want to convert a PWM signal to a 0-5V signal, you'll need a low pass filter.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Driving a temp gauge from aux 1

Post by stevieturbo »

Seems bizarre such a sensor would only last so long ? Are they Chinese or OEM parts ?

Do you actually have the gauge working off a PWM output signal at present ? You seem to say the signal is not smooth.....why would it not be smooth ?

Is the error you are seeing a problem with the gauge, or the signal you are sending ?

ie. If you send it what you believe to be 80degC constant.....is the gage steady or varying ? Sounds more like a gauge issue ? Or why 400Hz, what about higher or lower ?
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Driving a temp gauge from aux 1

Post by Rob Stevens »

Tried llower frequency no better, 400 is max. Tried capacitor and inductor to ground, this raised the values on the dash but they are still not stable. So gave up and fitted a new OEM sensor, display now stable but still under reads by around 15 deg, oh well, I can live with that.
Post Reply