Coolant tempurature monitor

I am going on a trip on the middle of july, I made the same trip last year and found that the old bike got a little on the warm side (hot day and traffic at the end of 180 mile trip). The coolant system has 2 temp sensor by the wax based thermostat which I housed in aluminium casing, and you can see where this is going. I am thinking a thermistor of some description would fit the bill, it would be nice to be able to read negative temps for cold morning starting but not crucial, it will how ever have to read well above 100 degrees C as the fan should cut in at 110*C.

the idea is to push the thermistor (or other sensor) against the aluminium body, it wont give a fast response to temp but should give an approximate idea of what is going on.

so what sort of sensor would be best? Degree level should be fine but 1 decimal resolution would be nice.

Get yourself a OLED display a PICAXE and one of these http://www.ebay.co.uk/itm/DS18B20-Waterproof-Digital-Probe-Temperature-Sensor-Thermometer-Thermal-Module-/281392057533?pt=LH_DefaultDomain_3&hash=item4184460cbd and you can read and display temperature between an operating range of: -55°C - +125°C

Easy to link to the PICAXE as it has an inbuilt function. Accuracy and resolution is very good, more than enough for most applications.

I use three ds18b20's on my classic v8.
One on a cylinder head for engine overheat warning.
2nd fitted into a sealed tube inserted in the radiator for pwm electric fan speed control.
3rd for outside air temp display.

The cylinder head one can go over 100c when engine stopped.
Neil.

I did think about the good old ds18b20, but the temp warning light comes on at 117 (I had this last year), getting close to the limit of the device. I don't know if exposing it to higher than max temp will cause issues or damage of some description which is why I was thinking about a different sensor that would not suffer in any way at very how temps.

once I have that side of things tied down I can think about other things like air temp and maybe a clock (bike doesn't have one). I did have a suggestion for exhaust temp, across all four ports to be able to see any fault that maybe developing before they become and issue - over kill but sounds really cool, there are actually port on the exhaust headers as standard that could be used but the gas coming out of there is very very very hot, like over 1000* when the motor is working hard.

I will order some sensors and nock a test bed together and see how things go

I have been thinking about this a little more, before I go ahead and finalise an order for parts, I have been thinking about adding in a charge meter. the simplest way for that is to take the switched live from the bike (which will power everything in the end) and run it through a voltage divider, to problem is that if a charging fault occurs a lot of voltage could still run through the picaxe ADC pin. any ideas how to protect it? the only one I have come up with is a zenner diode in parallel to the second resistor so that excess voltage will run through there. but I am not sure that will stop the voltage running though the picaxe at the same time.

..that will be good enough IMHO - use a 5v1 zener.

The excess voltage doesn't "run through the zener"...the zener will clamp the voltage to 5.1v across the lower resistor and hence the PICAXE pin

The most important thing here is that your temp sensor is encased on a waterproof, ruggedized case.
And I would think that an accuracy (do not confuse with resolution, they are not the same) of 1-C should be sufficient for your application.

Now, for the battery charge/discharge meter......you need a CURRENT sensor. The best is to use an AC712 variant, the current loop is fully isolated from the output.

And indeed, with an RTC, you could also display the actual time, or running time....whatever.

That is the beauty of the Picaxe.....so many neat things that can be done!

charging faults are normally found with voltage issue. both the factory and Haynes manuals show accepted voltage ranges at specified RPM. the voltage at those RPMs then dictate what is checked next, if it over voltage then the chances are that the req/rec is dead but with under voltage the alternator must be check which normally gives off around 100ac @ 5000rpm, if that shows corrected resistance readings are taken for each coil (3 phase alternator) before it is deduced that the reg/rec is again the issue.

the idea isn't to check battery condition or discharge rate, its more of a charge monitor to make sure the battery isn't damaged (by over voltage, under voltage isn't such a big problem). the problem with measuring the current is that the entire bike is draining current from the same source, inclusive of the battery charging, lights, engine electronics, clocks. for that reason measuring current you will just end up with the amount of current that the bike is using total.

I am not overly concerned about accuracy due to the delay of heating the casing that the sensors are pressed against. thermostat housing is under the tank and doesn't normally suffer from moisture issue, any water that get in there dries off quickly from the heat of the engine. however I may add some other temp sensors for fun, currently thinking that the system will have thermostat housing temp, radiator temp, air temp and voltage.