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4-channel TC meter and datalogger project
Randy G


endlesscycles wrote:
Holy cow, that thing is awesome!

I thought the same thing. I wonder how well the "PID" function works on it and whether it has auto-tuning

Life's too short to drink bad coffee.
That reflow gizmo: frankly it looks very good, and very cheap. Even if their firmware is terrible, we could re-program it however you would like -- I use that type of cpu chip in my 'day job'.

But the Arduino is a lot more popular these days, so I'll continue on with Arduino for now.
Edited by bvwelch on 05/18/2010 12:47 PM
Progress report: testing with 700 F soldering iron went well today - looks like I had a combination of software bug and also needed a ground wire in the circuit. Will try another test roast soon.
Randy G
Don't want to sound impatient, and do not mean to be, but can you guess at a time frame when it will be ready? I am trying to decide whether I should spend money on my Omega dual channel temp logger or wait for this... THANKS!

Life's too short to drink bad coffee.
Thank you for your interest, and I don't mind your question at all.

But what are you looking for as a first 'phase' ? In other words, when you ask 'when it will be ready', we need to define 'it' and also 'ready'.

Do you want a 'kit' or do you want a fully assembled unit?
Edited by bvwelch on 05/18/2010 9:05 PM
I hope to do another roast in the morning.

Meanwhile, some of you may be wondering what's under the hood. I'll put together a parts list soon, but if you're curious, you can browse the offerings at this web site, where I've been buying some of the parts:


The 'engine' is one of the Arduino boards. There are various tradeoffs - do you want all-in-one, with lots of room to experiment, built-in USB, etc? Or do you want the smallest unit possible, say to cram it into a hand-held box?

Besides the Arduino, we need a board to interface to the thermocouples. Here is the one I am using now:


If you want an LCD display, you can look at the ones they offer to get a feel for what is available.
Randy G
re: time frame... Ayedunno.. whatever. I am in no terrible hurry at all. At the moment I am hand-recording three temperatures every 30 seconds for roasts of around 13 to 15 minutes or so. I have a feeling that my Omega meter has a bad IR sender and the computer cannot see it. Would rather wait for this device than spend the $$ to replace the Omega.. So, whenever it happens it will happen. If it can display two or three temperatures on a real-time graph and save the data in a file (csv, I assume) then I will be ahead of the game.

I should have my two thermocouples installed in my Hottop some time by the end of next week, so when you have a beta package ready let me know if you need me.

What I want- The basics- Just an interface that will send the thermocouple information through a USB port to my laptop. Are you working on control of the roaster at this time? I would be happy with data collection and a real-time graph display at this point. The ability for some folks to have the LCD display is understandable, but it adds an expense.
Edited by Randy G on 05/18/2010 10:26 PM

Life's too short to drink bad coffee.


endlesscycles wrote:


randytsuch wrote:

I have one at home ;).
I was not able to find one for sale in the states, so I ordered one from CS.


Brand? Model#?

It's strange, there is no brand name or model number on the meter, or on the box.

The first goal is reasonably accurate temperatures. The board has 4 channels, and is already sending data to the PC.

The LCD is also working, but is optional.

Sending the data to the PC and storing it in a file with CSV format is easy too, but viewing real-time requires some sort of program on your laptop to be running.

What sort of laptop do you have? Windows? Mac, Linux? And what kind of software might you already have? Python, Java?

Any suggestions for PC software would be welcome.

If I were going to write something from scratch, Python would be easy for me. But we may be able to leverage some existing programs out there, at least for the near term.

I've seen various 'oscilloscope' programs that mention Arduino, but I haven't looked closely at any of them yet.
We may be able to use the same PC code that many other Arduino projects use -- Here's a coffee-related example.

Note-- it is the PC real-time display that I'm interested in, not so much the Arduino code.

Randy G
I have PCs. The software that the CoffeeSnob meter runs is impressive and I have seen it used by another meter/application/website somewhere (can't remember where), so I think they modified it for themselves.

Life's too short to drink bad coffee.


Randy G wrote:
I have PCs. The software that the CoffeeSnob meter runs is impressive and I have seen it used by another meter/application/website somewhere (can't remember where), so I think they modified it for themselves.

The only drawback to the CS SW is that I think you can only view one temp probe realtime. There is also a excel spreadsheet for it, and I have a kludged version of that to view BT, ET and ET-BT post roast.

I also remember that someone modded the SW for a different meter, I think it was in the meter thread. I think Andy will let you have the source code if you ask.

FYI, the other program I linked to was written in Python, from what I remember.

Lots of ideas for graphing on the PC, from Arduino, etc. here:

Edited by bvwelch on 05/19/2010 10:20 AM
Hi Guys,

there is another good bit of software that also uses the same meter series here http://homepage.n...logger.htm I havn't tried it yet but it can take two meter inputs and the cool thing it can take an OCR input from a display using a webcam

Some benefits over the CS software but the temp rise/min is a great feature of the CS one.
My name is Tim and I have a coffee equipment addiction problem smile

Two Hottops - modded
TJ 067 Electric 1kg 5+years old
Insert new 5-8kg Roaster here urgently BBQ grill
Good news - the test roast went very well today - the readings are accurate, and the rise-o-meter is very handy. The program is logging on the serial port also, as well as outputting to the LCD.

I'll be looking at some real-time graphing on the PC next. But meanwhile we could at least log the serial data with any serial capture program such as Hyperterm, Putty, etc.

I'll try and get some more tests in tomorrow.

I also tried out a nice panel-mount 'jack' today:


It worked well, and allowed me to quickly check the Arduino's temp reading against my old hand-held meter.
great thread

I'm playing guitar while I'm reading this. Three of my hobbies at once.
Good progress today -- The first 'rough cut' of the PC software is running. Using 'Processing' worked out very well.

At this point, all of the pieces have been proven to work, and I'm looking to hear from you if you want to help out with testing.

I had hoped to get some photos up and a step-by-step description of building a 'breadboard' version of the project, but electrical storms have moved in tonight. I've got family commitments for the next few days but I'll work on the project as time permits.
This thread has inspired me to learn about circuits and controls. Thank you.
-Marshall Hance
Asheville, NC
If someone is new to circuits and software, I'd for sure start him with Processing and Arduino.

Both Processing (PC side) and Arduino (embedded microcontroller), have easy to install IDE (integrated development environment). They are based on JAVA, which isn't a personal favorite of mine, but I have to say, it works well, and is multi-platform: Windows, Mac, Linux.

First, install the Processing IDE from here:

Then the Arduino IDE from here:

Next you'll want an Arduino board, and you've got some choices:

1) Always tethered to PC via USB? then may as well go with this one: http://www.modern...uemilanove

2) battery-operated, small size, low-power. Again, many choices. Here's a nice, yet inexpensive one: http://www.modern...le-package

3) Want something even smaller? http://www.modern...s/rbbb-kit

4) with optional radio? http://www.modern...eenode-kit

5) another choice for breadboarding (also a great site for project ideas): http://www.ladyad...boarduino/

Then head down to Radio Shack, pick up one of those white breadboards, some LEDs, jumper wires, and have a ball. Self-paced learning: http://www.ladyad...n/arduino/
Edited by bvwelch on 05/20/2010 8:49 PM
Thanks for all the information and work Bill.

I'm leaning towards getting the Duilmilanove board with the ATmega328. I don't plan to run from battery, will with use a 9V supply, or run off of USB, and size isn't an issue for me.

I need to figure out what display I'm going to use.

Hi Randy, thanks for joining in on the fun!

I just took a closer look at the Duemilanove board - it is a 5 volt system, which is OK, we just need to be careful with our documentation and provide both 5 volt and 3.3 volt options -- some of us will run 3.3 volt systems to be more efficient with batteries.

The mcp3424 module I'm testing, should work fine in a 5 volt system, you may need to connect the 5 volts to the pin labeled '3.3 volts'. The mc3424 chip itself doesn't mind 5 volts. I can test this when I get back on the work bench.

Just about any LCD should work - I'm using some old junkers that I had from years ago. 4x20 would be nice, or even a graphical one, but right now I'm using a cheap 1x16 (which from software looks like 2x8).

We can work up wiring diagrams for various LCD options - even 6-wire will work, since you've got so many I/O pins available. I've also used an I2C module, and there are 'serial' LCDs available too.

I haven't decided on a keypad/buttons yet. Milowe mentioned some game console but I haven't checked into that yet.
Edited by bvwelch on 05/21/2010 9:37 PM


bvwelch wrote:
I haven't decided on a keypad/buttons yet. Milowe mentioned some game console but I haven't checked into that yet.

I was doing some searching today, and there was a wii nunchuck adapter for $4 with free shipping. Since I ahve a wii, that would work great for me, but I don't know how many others have wii's.

Hi Randy,

I was thinking of older game devices that might be found at yard sales, but the wii sounds neat. I don't have one myself.

However, it's OK if we have different I/O and configurations. Maybe we'll eventually have a forum section with different measurement/pid projects similar to the various roaster projects.

We can plan on providing several examples. Here are a few, no doubt folks can think up better ones:

1) dedicated 4-channel data logger. No LCD or keypad, with USB cable and PC software with real-time graphing and logging to CSV file.

2) two-channel 'hand-held' LCD with rise-o-meter. Will also log to PC as in #1 above.

3) add keypad or buttons to #2?

4) local eeprom storage and then dump to PC later.

5) pid

Project status: #1 is working but graph is very basic-- needs a grid, etc. #2 working also. Needs documentation, screenshots, photos for both.
Edited by bvwelch on 05/22/2010 7:05 AM


bvwelch wrote:

2) two-channel 'hand-held' LCD with rise-o-meter. Will also log to PC as in #1 above.

A while back I was planning on building the rate of rise unit posted on HB. This is the only feature I'm interested in at the moment. Any idea if the two-channel hand-held rise-o-meter you are referencing above would be as inexpensive and also would it require less assembly?


1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Hi Allen, seems like there were 2 or 3 variations of rise-o-meter circuits mentioned on HB, so it is hard to compare to what we're doing here without specifics. I wouldn't mind seeing a nice summary and comparison of the HB projects and this one.
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