I'm working on adapting an LCD panel to replace the broken gauges on my motorcycle. In the process of doing so, I've been learning about the Arduino stuff, and related sensors.
I want to monitor the oil and coolant temps on my engine as well as the ambient air temp. I found the 18B20 chip is a really neat one, it can be daisy chained together since each has a unique 64 bit serial #. This would minimize wiring. I know I can use it as-is for ambient temp, but I got to thinking it could also be used as a fluid temp sensor if properly prepared and protected.
I have a few of these on order. My plan is to get some brass pipe plugs and drill out the tops, insert the 18B20, and then use some high temp epoxy to seal them in. This is similar to existing automotive sensors I've seen, and perhaps a little more compact.
The 18B20 is rated as working from -55C to +125C (-67F to +257F). This would work for all coolant systems, and most oil systems.
Are there any drawbacks to this idea based on anyone that has used the 18B20? I don't have them in hand yet, but thought about this & wanted to get some feedback.
Check that your LCD panel still works under typical summer and winter conditions' for your location.
Some of them turn black if they get too hot and suffer from slow refresh if too cold.
An LED display may be more robust. See http://octanereport.com/upload/image/2010/06/formula-one-steering-wheel-000.jpg
LEDs also give you colour options.
As robtillaart pointed out you can buy them from the Arduino Direct store in China and just this week Adafruit (based in NYC) added them to their store as well:
Waterproof DS18B20 Digital temperature sensor + extras
As far as gotchas go I would test a few to see if the reaction time is OK for your needs, the DS18B20 tends to be slow to adjust to a change in temperature. I would also watch the cable insulation as Adadfruit points out:
While the sensor is good up to 125°C the cable is jacketed in PVC so we suggest keeping it under 100°C.
Those waterproof sensors are great, but there's no way to mount them in a fluid line. I think what I want to do will work- just drill out a 1/8 pipe plug, seat the 18B20 in it, fill with epoxy, and wire in a connector.
You could buy a normal sensor and drill that out. You need to measure the fluid temperature, not the surrounding metal, or surface temperature, which is why drilling out a 1/8 plug might not work.
The other option is mapping the existing sensor and read it with an analogue input.
I'm going down this path to replace the existing idiot light in an american classic with a more intelligent offering.
