I like the circuit shown in post #16, except that an actual voltage regulator instead of a shunt zener diode will be a better choice. An actual regulator will be more stable and use less power. But do not leave out the 0.1 mfd bypass capacitors for the regulator.
But the gage indication may only be correct at one point if either or both of the temperature sensors are not linear. But most OEM gages are not actually calibrated other than "Hot" and "cold", so that may be close enough.
The capacitors of the correct value, as listed in the attachment, will work well.

 

The caps in the attachment will be ok for C2, C3, C5 but the pack doesn't seem to include any electrolytic caps.

But the gage indication may only be correct at one point if either or both of the temperature sensors are not linear.

That is indeed likely. I designed the circuit some years ago for adapting linearly-varying resistive fuel-senders with analogue gauges; not non-linear thermistor temperature-senders with possibly digital tech gauges.

 

The caps in the attachment will be ok for C2, C3, C5 but the pack doesn't seem to include any electrolytic caps.

That is indeed likely. I designed the circuit some years ago for adapting linearly-varying resistive fuel-senders with analogue gauges; not non-linear thermistor temperature-senders with possibly digital tech gauges.

Thanks I’ll search those up as well! I’ve got zenor diodes and all sorts of resistors. A trimmer resistor is that a variable one or just a 100 ohm resistor?

 

I like the circuit shown in post #16, except that an actual voltage regulator instead of a shunt zener diode will be a better choice. An actual regulator will be more stable and use less power. But do not leave out the 0.1 mfd bypass capacitors for the regulator.
But the gage indication may only be correct at one point if either or both of the temperature sensors are not linear. But most OEM gages are not actually calibrated other than "Hot" and "cold", so that may be close enough.
The capacitors of the correct value, as listed in the attachment, will work well.

What’s a voltage regulator? (told you I’m not very bright at this!)
not worried about power usage really. More concerned about heat but I don’t think that will be an issue at these amounts of power?

 

Will this box have the right capacitor for the electrolytic one?

 

A trimmer resistor is that a variable one

Yes.
Important: Do not use my circuit if the sender connects to a Body Control Module, or anything other than an old-fashioned analogue gauge, in your vehicle.

an actual voltage regulator instead of a shunt zener diode will be a better choice.

The zeners are intended merely as voltage limiters (15V), not regulators.

Will this box have the right capacitor for the electrolytic one?

Yes.

 

Yes.
Important: Do not use my circuit if the sender connects to a Body Control Module, or anything other than an old-fashioned analogue gauge, in your vehicle.

The zeners are intended merely as voltage limiters (15V), not regulators.

Yes.

Oh it’s an electronic gauge. I thought you had solved my problem. Thanks anyway. I take it it will break the gauge?

 

I take it it will break the gauge?

That's the risk. My circuit uses and generates voltages which may conflict with the unknown voltages and component ratings in your digital/electronic gauge.

 

That's the risk. My circuit uses and generates voltages which may conflict with the unknown voltages and component ratings in your digital/electronic gauge.

Ok I might risk it! It’s worth the $10 gauge exploding if it doesn’t like it. I need to make this work somehow and this is the best idea so far! No blame attached if it fails!
to add the gauge will stand 24v input to power it if that makes any difference?

 

I have a bit more information to add it might help.
that is the information I found for the gauge
along with the 0-2900 ohms from the sender.
many thanks again

 

At least a $10 punt, if you're happy with that, is better than the risk of damaging a $lots BCM !
I see the gauge input spec shows two resistance ranges; one ascending and one descending. Does the gauge have a switch/jumper to select which one is used? My circuit generates an emulated 0-190 Ohm resistance which varies in the same direction as the input 0-2900 Ohm resistance. The emulated resistance sinks current from the Gauge.
R2 will get quite warm, so allow for that when mounting it.

 

At least a $10 punt, if you're happy with that, is better than the risk of damaging a $lots BCM !
I see the gauge input spec shows two resistance ranges; one ascending and one descending. Does the gauge have a switch/jumper to select which one is used? My circuit generates an emulated 0-190 Ohm resistance which varies in the same direction as the input 0-2900 Ohm resistance. The emulated resistance sinks current from the Gauge.
R2 will get quite warm, so allow for that when mounting it.

Yes willing to risk $10 I wouldn’t be plugging it into an ECU on the truck that would be a $2000 gamble!
from playing about with a potentiometer it seems to work at both ranges in the same way. That bit is quite confusin.
however I’ve nearly got all the parts on order to try your circuit so once I’ve found the last part that will be ordered as well and I will put it together and come back with a result. Hopefully a nice gauge movement and not a burnt out gauge
many thanks for your help with this it’s much appreciate. Richard

 

If your new fuel sender doesn't fit the tank, why not make it fit? Over the years I've modified the arms on senders and the length of the down rod to make them fit. while this one doesn't match you gauge requirements it does show how they can be modified to fit any tank, Just study the picture to see.
https://www.speedwaymotors.com/Univ...EGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE

 

I will put it together and come back with a result.

Wire the trimmer resistor as a rheostat and set it mid-way initially. Then you can tweak it to adjust the emulation result to suit your meter scale. Never let the trimmer go below ~ 20 Ohms unless you include a fixed resistor of ~20 Ohms in series with it. Good luck.

 

Wire the trimmer resistor as a rheostat and set it mid-way initially. Then you can tweak it to adjust the emulation result to suit your meter scale. Never let the trimmer go below ~ 20 Ohms unless you include a fixed resistor of ~20 Ohms in series with it. Good luck.

Will do thanks

 

Hi again I’m slowly getting the circuit together! However the trimmer 100 ohm has 3 terminal. Where does the third one go to please?
many thanks again

 

Where does the third one go to please?
many thanks again

The device is a potentiometer where the middle terminal is the wiper that moves across the fixed resistance connected to other two terminals.
To use it as a variable resistor, connect the wiper terminal to one of the other terminals.

 

The device is a potentiometer where the middle terminal is the wiper that moves across the fixed resistance connected to other two terminals.
To use it as a variable resistor, connect the wiper terminal to one of the other terminals.

Thanks for that. Sorry for delay!
last question hopefully
what happens vcc-? Is that going to ground? Many thanks

 

what happens vcc-? Is that going to ground?

Yes.

 

OK, folks. lease consider that the TS is not an electronics person and thus the wonderful but rather complex circuits will be a challenge to assemble in a durable manner. This means that considering other methods that are simpler need to be considered. presently it is not even clear if the resistance versus temperature curves slope in the same direction.
So it is still a good idea to measure the resistance of the installed sensor at both cold temperature and at some hotter temperature. That will give two points on the curve, which can then hopefully be compared with the new sensor response.