Temperature sensor to measure surface temperature compatible with Raspberry Pi

Hi Kas,

bwelsby and I did some fairly extensive (at the time) tests on the Pi 3, we used a thermistor and also examined the in-built measurement.

The information is dotted in multiple posts and comments though:

See here Raspberry Pi 3 Dynamic Current Consumption, Power and Temperature Tests

and Raspberry Pi temperature and cooling testing Part 1 initial tests.

Raspberry Pi 3 temperature and cooling testing Part 2 with a HAT tests.

Raspberry Pi 3 Cooling / Heat Sink Ideas

As you say, there is no ADC so that makes it a bit awkward. An option is to attach one (SPI or I2C for example) or use a multimeter and pen/paper, if you're capturing data over slower periods. The thermistor was a bead, so I drilled a hole for it (in heatsink).

An alternative could be an RTD device (e.g. PT100), they are also tiny and some have a flat surface, so you could tape it onto the chip.

You could use a larger semiconductor device (e.g. TO-92 package) but they have a slow thermal response.

Just re-reading, I may have misunderstood your requirement.

If you're measuring the temperature of a different surface (i.e. not the Pi) then similar comments may apply, or you may need a different method (e.g. thermocouple) depending on the expected temperature of the target surface.

One example method is here, connected to the Pi:

Temperature Measurement for Lab and Science Projects

shabaz,

Thank you for the information in your blog. I was hoping to find something a bit simpler/cheaper. I am looking to sense the temperature of a wall in two locations. If I need to of these then the cost begins to climb quickly. If you have any further suggestions that would be great, I was looking at RTDs and then use an RTD to Digital board (Not much cheaper I guess) and was wondering if you or anyone else had any thoughts on this type of setup.

Kas

How about a DS18B20 one wire type digital sensor ?

Product LinkProduct Link

https://www.element14.com/community/community/stem-academy/blog/2014/12/13/raspberry-pi--ds18b20-temperature-sensor

There are many I2C sensors that could be used:

TMP102

MCP9808

Si705x

or spi sensors

LM74

MAX6662

DS1722

TC77

etc

Thank you for the information, Those are all great suggestions but I was hoping for a more complete solution especially for surface sensing. Something that has low thermal mass. But I think your suggestions have put me back on track and let me see that high cost/complete solution may not be needed.

Kas

Thank you.

Kas

Hi Kas,

For low thermal mass perhaps a very small SMD sized silicon sensor, or a thermocouple or thermistor or RTD as you say with small size. If you want to use on of the latter devices, then you'll need an ADC, and you could use the same ADC as in the project mentioned earlier, since they are available on a PCB at low cost from ebay, it is the ADS1118. Here is an example one: ADS1118 16-bit AD Converter ADC SPI Communication Module Development Board | eBay

RTDs are available as small flat devices, so could be taped onto a wall for example. Another approach could be non-contact IR thermal sensing.