#Get a Slack message when a limit is crossed

Post to a Slack channel when a reading crosses a value. The test keeps running.

#Before you start

• A Slack connector on Connectors in the console. Its bot needs the chat:write scope. See Slack.
• The bot invited to the channel it posts in.
• A Trellis setup you can deploy from Phloem Computer. See Trellis.

#Steps

1. In the console, open Alerts and choose New role.

2. Type a role name, such as test-conductor. Use lowercase letters, digits, - or _.

3. Pick your Slack connector in choose a connector… and type the channel, such as #test-alerts. To post in more places, press + another channel.

4. Press Save.

5. In Computer, open Trellis and open your setup in Code. Add an alarm that names the role in notify=:

   Copysetup("heater")
   
   ch = channels()
   ch.read("/demo/temperature", unit="degC")
   
   alarm(
       "too_hot",
       when=ch["/demo/temperature"].above(80),
       severity="warn",
       notify=["test-conductor"],
   )
   
   page("Heater test", layout=col(alarms()))

   when	above(x), below(x), within(lo, hi) or outside(lo, hi) on a channel
   severity	info, warn or critical
   notify	role names from Alerts

6. Press Deploy.

#Check it worked

When the alarm fires, Slack gets a message such as [warn] too_hot on /demo/temperature …, with how long ago it fired.

On Alerts, Recent deliveries lists each firing and its outcome:

Updated November 6, 2026