TH7

Seven-channel multiple thermocouple reader and logger HAT for the Raspberry Pi.

This software supports the following thermocouple types:

• B
• E
• J
• K
• N
• R
• S
• T

Features not yet implemented but planned:

• More database logging options than SQLite3 and InfluxDB
• Advanced filtering, incl. user-selectable filtering stages and sample sizes
• Several logging options at once, one local, one or more remote
• Configure any setting via API call either via RESTful JSON API or GRPC
• A terminal user interface ("TUI") that may be used to remotely monitor/access/configure a TH7 (w/ auth)
• Ability to act in headless mode
• Request dumps from filter stages for noise study
• ... and more!

Note: Most thermocouples that have a coloured and a white lead, usually have the coloured one as the positive.

Configuring the TH7

This program is controlled with a config file config.toml in which the user can configure each thermocouple channel independently, enable a web view, configure database logging, etc. The TH7 software uses sane default values where possible.

# EXAMPLE TH7 CONFIG
[TH7]
port = 9090   # port used by the web view
LED = true    # enable the blinking lights on the Raspberry Pi Hat
debug = false # if true, the software will use a simulated TH7
nolog = false # debug variable, will simulate a DB
noweb = false # set to true to disable web view and the REST API

# Configure channel 1
[Channel_1]
type = 'K'    # set type to K-type thermocouple
gain = 106.8  # gain is used during signal conversion
offset = -5.6 # offset is added to the final converted value (in °C)
filter.samples = 50 # samples for the filter function
filter.type = 0     # integer representing the filter function type
log = false # do not log this channel to DB (if applicable)

# Filter functions:
# 0: simple alpha-beta filter (default)
# 1: lag filter: old * 0.90 + new * 0.10
# 2: lag filter: old * 0.95 + new * 0.05
# 3: lag filter: old * 0.99 + new * 0.01

# Configure channel 2 to read μV
# this example uses default values for gain, offset and filter.
[Channel_2]
type = 'U' # set thermocouple type to 'U' to just read μV

# Database
# Each database type requires its own set of values
# Below is an example for SQLite3
[DB]
type = "sqlite3"
path = "/home/pi/th7.db" # where to save the database file
freq = 60 # logging frequency. specified in seconds

# InfluxDB example
[DB]
type = "influxdb"
host = "https://influxdb-server.com/"
bucket = "my-th7-bucket"
token = "cGFzc3dvcmQxMjMKcGFzc3dvcmQxMjMK"

Using InfluxDB

The host, bucket and token fields may be specified in the env variables, rather than in the config.toml file. Example:

export INFLUXDB_HOST="https://influxdb-server.com/"
export INFLUXDB_BUCKET="my-th7-bucket"
export INFLUXDB_TOKEN="cGFzc3dvcmQxMjMKcGFzc3dvcmQxMjMK"

In this case, the [DB] field in config.toml can be left empty except for type = "influxdb"

Building on a Raspberry Pi

This code builds without fuss on Raspberry Pi 4 with go version go1.19.3 linux/arm

wget https://go.dev/dl/go1.19.3.linux-armv6l.tar.gz
sudo rm -rf /usr/local/go && sudo tar -C /usr/local -xzf go1.19.3.linux-armv6l.tar.gz

edit $HOME/.profile and add the following, if not already there:

export PATH=$PATH:/usr/local/go/bin

source new profile

. $HOME/.profile

then try to build

make