Wireless, Bluetooth, High-Temperature Thermometer

Hello,

I am trying to assess how to create a wireless bluetooth (and potentially wi-fi enabled as well) high-temperature thermometer.

I have looked up sensors, namely DHT type, and also ways to run an arduino with battery power.

I am not sure how to have the microcontroller be available via bluetooth without draining battery power. Is this possible?

Also, I'd like the option for the microcontroller to be configured to connect to a local wifi network if it's available. This would happen from the client-side, meaning they'd connect via bluetooth and somehow set the wifi/password through their client device (e.g. smart phone).

I only need temperature readings periodically - say, every 5 or 10 minutes or so. But having the device available to connect via bluetooth, from a smart phone for example, may require constant activity? I'm not sure.

I say high temperature because I plan to use this inside of a sauna, which can reach upwards of 200 degrees fahrenheit. But it seems the DHT sensors I've seen so far have that within their operating temps.

Thanks in advance

bttf: But having the device available to connect via bluetooth, from a smart phone for example, may require constant activity?

Bluetooth has to be alive in order for Android to make the connection. You might find that using a NODE-MCU is a better choice, simply because of the user interface.

A sauna has high temperatures but ALSO high humidity. You have to deal with that, too, and protect your electronics accordingly. The DHT22 sensor can handle 100% (or so it says - mine never seem to get over 99.9% for whatever reason). If you're not interested in the humidity, you may be better off by using a much cheaper, more robust and potentially even more accurate thermistor instead. It just needs a little bit more calculation on the Arduino side.

For the WiFi, indeed a NodeMCU (or WeMOS D1 or other ESP8266 based board) would be a natural fit. They have WiFi built in, and can run reasonably efficient on battery power. Much better efficiency you'll be able to get by using the bare bones ESP8266 processor. Have it sleep, then wake up periodically to read the temperature, send it to the server, and go back to sleep. Be aware that WiFi (and Bluetooth and any other wireless communication) takes quite some power. Your phone could then connect to the server to retrieve the data any time.

In the case that it's connected to wi-fi, I could certainly have it send temperature stats to a server somewhere.

But in the case of bluetooth, I was hoping it could connect to a phone directly and an app on the phone would be able to read and display. Is this not possible with a low-power configuration? Ideally I'd want the battery (2 AAs for example) to last for at least a couple months.

But in the case of bluetooth, I was hoping it could connect to a phone directly and an app on the phone would be able to read and display. Is this not possible with a low-power configuration? Ideally I'd want the battery (2 AAs for example) to last for at least a couple months.

The TI Sensortag is a Bluetooth Low Energy tag powered by a coin cell battery with temp, humidity, accelerometer, gyro, etc. sensors. Free IOS and Android apps are available to read from the tag. The tag is a demo project for a TI BLE chip so I am not sure how reliable it is. I have no idea how long it will last in a 200 degree sauna.

it would be a lot easier to put the sensors inside of the sauna an the electronics outside.
also, since the sauna is fixed and has lights, you can tie in power without batteries. For what you ask, batteries are more of an advanced project and are not required in this application. desired, maybe, but since you are in close proximity to a power source, not required.

as a note, the fresh air intake is low and MUCH colder than the warm air at the top. the difference from floor to ceiling can be as much as 20 degrees.