First Prototype K Type Thermocouple Data Logger

[awalker]

So have knocked up a quick prototype

Currently logs data from two different thermocouples (even though I currently only have one!)



Arduino Uno
Arduino Shield Data logger (SD card reader/writer with Real Time Clock)
Two MAX31855 boards
Only one thermocouple at present

Basic software logs temp from both MAX31855 and their junction temperature (close to ambient)
The 1000 reading is due to no thermocouple connected to that MAX31855



Did a quick test with gas oven and converted it with Excel



The idea is to now add a display which if it works should be cool

Next Steps
    Add a way of starting/stopping data logging.
    Choose which thermocouple is displayed on the display

[spinal]

Nice... what sort of costs are you looking at? Are you planning on having it permanently installed, or only plugged in when in use?

I've got 4 TCs in my oven, but never really connected them to anything as I couldn't find a way to waterproof the recorder or get power to it 24/7 (for some odd reason, I wanted to embed the screen into the side of the oven and not have something "hot pluggable")

[awalker]

Will check on costs, and update tonight.

Probably will have it removable. Like you I was wanting a screen, to see current temp and a temp over time graph.

But I am going to go WiFi/ethernet so you can connect to it via phone or tablet. See the graph on that instead.

Just current temp on display. Like you was dubious about it being water tight or moisture getting in it and misting display up.

[purrcat]

Interesting idea.

A couple of years ago I built various units to monitor solar power generation and energy usage in the house using real time voltage and current sensors using arduino. Open Energy Monitor Organisation do various arduino based kits which can take a set of temperature feeds and transmit the measurements wirelessly or even simply send them directly to the web.

My energy monitor system sends data to an LCD display which constantly shows me power generated as well as consumed so it wouldn't be too much of a stretch to transmit temperature thermocouple data in the same way. If the data was transmitted to their EmonCMS site a real time display can be generated and seen on any device capable of displaying web pages. That way you wouldn't need work out how to display the data on the web.

In my energy system I monitor hot water cylinder temperatures but find that its difficult to get accurate measurements due to poor contact with the tank. How do you go about implanting the temperature sensors within the oven?

[awalker]

Sept 1, 2015 15:28:02 GMT purrcat said:

Interesting idea.

A couple of years ago I built various units to monitor solar power generation and energy usage in the house using real time voltage and current sensors using arduino. Open Energy Monitor Organisation do various arduino based kits which can take a set of temperature feeds and transmit the measurements wirelessly or even simply send them directly to the web.

My energy monitor system sends data to an LCD display which constantly shows me power generated as well as consumed so it wouldn't be too much of a stretch to transmit temperature thermocouple data in the same way. If the data was transmitted to their EmonCMS site a real time display can be generated and seen on any device capable of displaying web pages. That way you wouldn't need work out how to display the data on the web.

In my energy system I monitor hot water cylinder temperatures but find that its difficult to get accurate measurements due to poor contact with the tank. How do you go about implanting the temperature sensors within the oven?

Sounds like an interesting project, as you say not much of a stretch to have it on an LCD.
I have something else planned for the display.

Sparkfun have a free site you can upload data to data.sparkfun.com

Placement of sensors is something, I am not sure of yet. But will be building a new oven next year so want to implant them (and spares) at build time.
Will probably go for floor sensors front and back of barrel oven.

But am open to ideas as want to do it right!

[awalker]

Sept 1, 2015 6:53:23 GMT spinal said:

Nice... what sort of costs are you looking at? Are you planning on having it permanently installed, or only plugged in when in use?

I've got 4 TCs in my oven, but never really connected them to anything as I couldn't find a way to waterproof the recorder or get power to it 24/7 (for some odd reason, I wanted to embed the screen into the side of the oven and not have something "hot pluggable")

Arduino Uno £5
Datalogger Shield £5
K Type Thermocouple (600oC) 3M £5
MAX31855 PCB £20
SD Card £2

So £37 so far, this is for one thermocouple

Hopefully can bring the price down on the MAX31855 boards in the future

[spinal]

Tempting...

Ian - for placement, it's really a "while you build" thing. Retrospective placement would mean drilling the dome! :eek:

I placed 4 sensors when building (under insulation in the floor, between insulation and floor fire bricks, in a gap between bricks in dome and outside dome bricks, but inside insulation). The idea was, I could get floor and dome temps of the bricks, as well as internal over temperature (as close as possible). The fourth, under the floor insulation was to see how effective the floor insulation was.

Never actually wired them to anything though! Thermocouples are pretty cheap, iirc I bought 999c ones for £2-£3 each... but only a 1m cable

[purrcat]

Sept 1, 2015 21:52:14 GMT spinal said:

Tempting...

Ian - for placement, it's really a "while you build" thing. Retrospective placement would mean drilling the dome! :eek:

I placed 4 sensors when building (under insulation in the floor, between insulation and floor fire bricks, in a gap between bricks in dome and outside dome bricks, but inside insulation). The idea was, I could get floor and dome temps of the bricks, as well as internal over temperature (as close as possible). The fourth, under the floor insulation was to see how effective the floor insulation was.

Never actually wired them to anything though! Thermocouples are pretty cheap, iirc I bought 999c ones for £2-£3 each... but only a 1m cable

I had no idea that these thermo couples were so cheap!

It seems like I could wire in four of them and terminate the connections on a weather protected connector under the base and simply plug a monitor in:

A unit such as this would suffice - I simply need to put a serial connector between the sensors and the display and then, within reason the measurement unit can be placed wherever I want.

www.ebay.co.uk/itm/4-Channel-K-Type-Digital-Thermocouple-Thermometers-Sensor-Probe-2501-F-battery-/221844674172?hash=item33a6f9167c

This definitely seems like a good addition and, considering the cost of the oven, it's "buttons" in terms of extra cost!

[dougclay]

Wow, I haven't been on here in a while... Was just "driving by" when I was amazed to see somebody else actually talking about this subject I had to login to say hi..

I built an arduino logger back in 2012, logging from 4x MAX31855.
Actually the first one didn't log much but it displayed values on an LCD 2x40 character display.
I later added an microsd card by soldering pins into the tabs of an sd-card adapter

That was then, I since started afresh with a Raspberry Pi and boy is it a lot easier!!!
Same 4x MAX31855 and LCD, but now with built in wifi accessible webserver and data logging using RRD (rrdtool) to log and provide graphs. Raspi can do many languages but I found python easiest. Means you can do almost anything from send notifications to your phone to say we're up to temperature or that the temperature dropped and we need another log for the fire

There are dozens of larger LCD screen options for the Pi, would be very easy upgrade.

Never thought about making anything weatherproof as it's easy enough to plug in and go when you need.

When is comes to thermocouples, they seem to be getting a lot cheaper... I got a couple of these:
www.ebay.co.uk/itm/3M-K-type-100-1250-Thermocouple-Control-Temperature-Controller-Sensors-Probe-UK-/370876027770?hash=item5659ef137a

They come with 3 meters of cable which was more than I needed and as the cable is made of the 2 different types of metal all the way along, I made extra thermocouples by simply cutting and twisting new lengths together. This was useful when testing the code on the logger, I made 4 mini thermocouples with a few centimeters clipped of a spare length. I used the probe in the dome, but the ones under the floor are all "homemade".


Glad to see some more interest in the subject after all these years

Aug 12, 2012 13:18:40 GMT dougclay said:

...I guess it's too geeky for this forum... wrong kind of breadboard and not oven chips ;-)

Cheers

Doug

[awalker]

Nice doug . You got any pictures?