der Automat
machine
A device that independently dispenses goods or provides a service after payment or at the push of a button.
Ich muss noch Geld am Automaten abheben.
I still need to withdraw money from the ATM.

machine / automaton
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machine
A device that independently dispenses goods or provides a service after payment or at the push of a button.
Ich muss noch Geld am Automaten abheben.
I still need to withdraw money from the ATM.

'Automat' is often the second part of a compound noun. The first part describes what you get from the machine, e.g. 'Geldautomat' (ATM), 'Fahrkartenautomat' (ticket machine), or 'Snackautomat' (snack machine).
Der Fahrkartenautomat ist leider kaputt.
Unfortunately, the ticket machine is broken.
Common verbs used in connection with machines are 'Geld abheben' (to withdraw money), 'ein Ticket ziehen' (to get a ticket), or 'etwas aus dem Automaten holen' (to get something from the machine).
Du kannst an fast jedem Geldautomaten Geld abheben.
You can withdraw money at almost any ATM.
To indicate a location, you use 'am Automaten' (at the machine, dative). To express movement toward it, you say 'zum Automaten' (to the machine, dative).
Ich warte auf dich am Automaten.
I'll wait for you at the machine.
The meaning 'person who acts mechanically' is a metaphor. It is often introduced with the comparison word 'wie' (like) to describe emotionless behavior.
Er erledigte seine Arbeit wie ein Automat, ohne nachzudenken.
He did his work like an automaton, without thinking.
device / apparatus
'das Gerät' and 'der Automat' both refer to technical objects. However, 'Gerät' is much more general: it can be almost any technical apparatus. An 'Automat' is a specific kind of device that independently dispenses something or performs a service after a button is pressed, a card is used, or payment is made. The words can be confused because every 'Automat' is a 'Gerät'. But not every 'Gerät' is an 'Automat'. If the thing automatically gives out goods or provides a service, 'Automat' is more precise.

Nach der Arbeit zieht Tom eine Fahrkarte am Automaten.
After work, Tom gets a ticket from the machine.
Sie benutzt das Gerät jeden Morgen, um Kaffee zu kochen.
She uses the device every morning to make coffee.