Hello!
There's a thermistor in my motorcycle that is there only to feed an analog indicator in the panel. The sensor is broken, since the indicator shows always the minimum, even after a long ride. I tested the indicator by grounding the sensor pin and it correctly goes to the maximum of the scale (H), so I guess it's working. I tested the sensor and it gives out very high resistance values, my guess is that the sensor is broken so I ordered a new one from spare parts.
Unfortunately, I can't find a sensor with the same range of resistance across the given interval of temperatures, but I calculated that with a downscale factor of arount 47 I could adapt the one I ordered to the range supported by the indicator.
Is there any way to scale down the output resistance of this sensor linearly? In other words, applying a dividing factor of 47 to the output resistance? 2000 ohm -> 42 ohm, 1600 ohm -> 34 ohm
You could use a fixed value resistor in combination with the thermistor to create a voltage divider. Feed the output voltage from that to an analog input of an Arduino. Write some code to read the analog voltage and output a PWM signal. The output would need to be connected to a transistor to drive the gauge (the voltages and currents the gauge needs will probably be unsuitable to connect it directly to an Arduino output).
Of course, this will be much more complex and so less reliable than the original circuit. A motorbike is a very harsh environment for electronics like an Arduino. You would need to provide a stable power supply for the circuit and protect all the inputs from voltage spikes and interference.
I was thinking of using a simple voltage divider. Assuming the gauge itself has a voltage divider through wich a voltage is applied to the needle based on the sensor resistance, I could even modify its resistance to fit my needs. But this is just theory, do you think it is feasible?
It's a long story. Trying to make it short my bike is 2001 but the engine block is newer, so it has a different sensor from the original one. It's weird but that's how it is, and I had to buy a spare part on ebay from a newer bike same model (2006).
I looked it on the service manual. 2001 hornet has a different sensor than mine (with a totally different connector) with these ranges: 80°C around 2kohm, 120°C around 600 ohm, while the sensor from the 2006 bike has these ranges: 80°C aroung 50 ohm, 120°C around 15 ohm. I couldn't find the sensor I need for my specific bike's year, so that's why I need to adapt it.
