Alarm Script Recipes

Steve M edited this page Aug 16, 2015 · 21 revisions

LinkMeter on the RaspberryPi has the ability to fire off user scripts when an alarm goes off. This is in addition to beeping the piezo buzzer. This requires some degree of Linux shell scripting expertise, but using some of these recipes might make things a little easier to understand.

A Note About Alarm Arming

To prevent alarms from turning on and off every time the temperature bounces back and forth across the alarm point there is a hysteresis. This means that the temperature must be outside of the alarm range by more than 1 degree before the alarm will "arm" and be capable of sounding.

Example: Your current temperature is 99.9, and you set the high alarm for 100 at this time. Your alarm is not armed yet and will not arm until is is a degree from the alarm threshold, that is below 99, say 98.9. Even if the temperature rises to 500 the alarm will not go off, as it was never armed.

Now assume the current temperature is 98.9, and you set the high alarm for 100. When it hits 100, the alarm will fire. Even if it drops back below 100, it will keep ringing until silenced. Silencing the alarm only silences the alarm. If the temperature drops below 99 again, the alarm will rearm, and then goes back over 100, the alarm fires again.

Action Will Ring Again? Must Re-Arm?
Press any button on HeaterMeter unit Yes Yes
Unplug the alarming probe Yes Yes
Clicking 'Silence' on web popup Yes Yes
Setting the trigger point to 0 with al_set Yes Yes
Open the lid until lid detect activates Yes No
Un-ticking Alarm 'On' in web config page No Yes
Setting the trigger point negative with al_set No Yes
Alarm Action = Silence Yes Yes
Alarm Action = Disable No Yes

Editing Scripts

Via Web

From the LinkMeter configuration website navigate to LinkMeter -> Alarm Scripts. Each script has its own reset / save button! Do not try to edit multiple scripts without saving each in between. The script will only run if the "Execute on alarm" box is checked at the time the alarm goes off (currently ringing alarms have no effect).


First of all, alarm scripts are located in /usr/share/linkmeter/. Do not edit the script named "alarm", as this file will be replaced every time LinkMeter is upgraded and you will lose all changes. Instead, create new files for your scripts. The system first looks for alarm-all, and executes that. If the return value of that script is zero (the default), the system looks for a file named alarm-{probeidx}{alarmtype}. To not execute the alarm-specific script, exit alarm-all with a non-zero return code (e.g. exit 1).

For example if the Pit probe high alarm is going off, it will look for alarm-0H. These files can be a shell scripts, lua scripts, or a regular ARM ELF binaries. These recipes can be used for either an alarm-specific or alarm-all file. The files must be executable, i.e. chmod +x or they will not be run.

There are many variables available to use in your scripts. From a command prompt execute lmclient LMCF for a list. In addition, the alarm system adds al_probe, al_type, al_thresh, pn (alarm probe name), pcurr (alarm probe current value) variables. The al_set function can be used to change the value of the current alarm.


All scripts

# The first line of any shell script must begin with the above #! line 
# Comments begin with #

Turn the alarm off

# Silence this alarm, it will ring again if re-armed
al_set 0


# Disable this alarm, it will not ring again
al_set -$al_thresh

HeaterMeter Control - Shutdown

Often you want to turn off the Pit when your food is done, this can be done automatically from the Alarms configuration page. However, this is also easily done using lmclient to send a command to HeaterMeter to change the setpoint.

# Lower the setpoint to 100
lmclient LMST,sp,100

HeaterMeter Control - Ramp Down

You can do more complicated setpoint control with a ramp down script.

case $al_thresh in
  180) NEWSP=215; NEWAL=190; ;;
  190) NEWSP=205; NEWAL=200; ;;
  200) NEWSP=100; NEWAL=0; ;;

lmclient LMST,sp,$NEWSP
al_set $NEWAL

HeaterMeter Control - Super Ramp Down

10 degrees too much? That's ok you can ramp down two degrees for every two degrees the meat climbs if you like

if [ "$al_thresh" -gt 199 ] ; then
  # done
  lmclient LMST,sp,100

lmclient LMST,sp,$NEWSP
al_set $NEWAL

Time Delays (UNTESTED)

Often you may not want be notified when the alarm happens but some time after it happens. Cron can be used. Note cron only has per-minute resolution so don't try to make things happen every N seconds. This example calls the alarm-all script 1 hour after the alarm triggers.

# If no parameter, this is a regular alarm
if [ -z "$1" ] ; then
  NOW=`date +%s`
  # Set target for 1 hour from now 3600=seconds

  TARGET=`date -D "%s" -d $WHEN +"%M %H %d %m"`
  echo "$TARGET * /usr/share/linkmeter/alarm-all RING${al_probe}" | crontab -

  # make sure cron is started, it won't start if there is no crontab at boot
  [ -z "$(pidof crond)" ] && /etc/init.d/cron start
  # This is the cron callback
  # Don't fire again
  crontab -r

  # Do whatever you want here, using another recipe

Alarm Script Variables

Common Variables

Variable Description
al_prep Preposition describing alarm (above/below)
al_probe Index of ringing alarm (0-3)
al_set FUNCTION change current alarm threshold
al_thresh Threshold of ringing alarm
al_type Type (L/H) of ringing alarm
sp Setpoint
pcurr Current temperature of ringing alarm
pcurr0, pcurr1, pcurr2, pcurr3 Current temperatures
pn0, pn1, pn2, pn3 Probe names

Configuration Variables

Variable Description
fmin, fmax Blower min/max
ip IP adddress of LinkMeter
lb LCD Backlight
lbn Home Mode
ld Lid detect duration
le0, le1, le2, le3 LED trigger/invert
lo Lid detect offset %
oflag PID output flags
palh0, palh1, palh2, palh3 Alarm high thresholds
pall0, pall1, pall2, pall3 Alarm low thresholds
pca0, pca1, pca2, pca3 Steinheart A coefficients
pcb0, pcb1, pcb2, pcb3 Steinheart B coefficients
pcc0, pcc1, pcc2, pcc3 Steinheart C coefficients
pcr0, pcr1, pcr2, pcr3 Steinheart resistances or thermocouple scale
pidb, pidp, pidi, pidd PID constants
po0, po1, po2, po3 Probe temperature offset (config)
prfn0, prfn1, prfn2, prfn3 Probe RF mapping
pt0, pt1, pt2, pt3 Probe type
smin, smax Servo min/max position (10us)
ucid HeaterMeter version

MSMTP Configuration

The mail transfer agent "msmtp" must be configured before any of the sendmail (email/SMS) commands will work. The web interface for this is under Services -> SMTP. If you prefer editing files, edit /etc/msmtprc with the information appropriate for your mail server

SMTP over SSL / Gmail

account default
port 465
auth on
tls on
tls_certcheck off
tls_starttls off
password password

Hotmail / Windows Live Mail

account default
port 587
tls on
tls_certcheck off
auth on
password password