The PTF Series PTFM101C1G0PTFM101C1G0 RTD from TE Connectivity is a platinum RTD making it very stable and accurate and it is tiny as shown in a previous blog, allowing it to respond quickly to temperature changes. Although the Nucleo MCUNucleo MCU has a 12 bit A/D converter, I wanted to implement an RTD interface with even higher accuracy. I chose a Maxim MAX31865MAX31865 chip which is specially designed to handle RTDs with its internal 15 bit A/D converter. This chip has an SPI interface and is mounted on a small circuit board:
Note the 2 solder bridges near the RTD that configure this card for 2-wire RTD operation. The wires to the sensor are so short, 2-wire mode should work fine.
A similar RTD cardRTD card is in the Newark catalog, but was not in stock for this order. Adafruit makes an arduino library for this chip and provides an example program. Unfortunately the example will not compile with the Nucleo as a target.
My interface card is compatible with both the Nucleo and standard arduinos, so I plugged the teperature sensor interface card into an Uno to see if it would work. The example program worked flawlessly, demonstrating the high performance of the RTD and also showed my interface card works with this sensor.
I removed the LCDs for this test because the arduino UNO runs on 5 volts and the LCDs run on 3.3 volts.
The temperature sensor card is designed to work on either voltage and seemed happy to be running at 3.3 volts even though the arduino was running at 5 volts.
Here is a quick video of it in action:
This milestone marks completion of demonstrations of all components in the project kit.
Now I can focus on getting the system working.
The next step will be to design the main chassis.
It may take some time as there are a lot of subsystems that need to fit on it and work together.
Relevant Links
Sixth Sense Design Challenge: About This Challenge
Sixth Sense Design Challenge: Technical Documents
GraffitiBot Project Blogs
Sixth Sense GraffitiBot - blog 1
Sixth Sense - Kit Unboxing and Other Parts - GraffitiBot blog 2
Sixth Sense - Sensor Circuits - GraffitiBot blog 3
Sixth Sense - Interfaces - GraffitiBot blog 4
Sixth Sense GraffitiBot - System Interconnect - blog 5
Sixth Sense GraffitiBot - Wheels & Motors - blog 6
Sixth Sense GraffitiBot - ST Sensor Tile App - blog 7
Sixth Sense - Load Cell PCB - GraffitiBot blog 8
Sixth Sense - Magnetic Angle Sensor - GraffitiBot - Blog 9
Sixth Sense - LCD Interface - GraffitiBot - blog 10
Sixth Sense - Pump Controller - GraffitiBot Blog 11
Sixth Sense Main Drive Motor - GraffitiBot - blog 12
Sixth Sense Motor Controller Mods - GraffitiBot blog 13
Sixth Sense - RTD - GraffitiBot Blog 14
Sixth Sense Mechanical Design - GraffitiBot Blog 15
Sixth Sense GraffitiBot Motor Wiring - Blog 16
Sixthe Sense GarffitiBot - First Dry Run - Blog17
Sixth Sense GraffitiBot Hydraulics - Blog 18
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