Cover, rollershutter over sonoff dual R2, set duration

Configuration
1

Hi all,
i change firmware of a sonos dual R2 and connect via mqtt to HA.

I define it as a cover in order to control a sun rollershutter (awning).
The motor who move the awning doesn’t report the position so i need, when i press the open or close button (and then via automation) define how many seconds the relays is in ON state.

How i can configure it?

cover:
  - platform: mqtt
    state_topic: "stat/sonoff02/POWER"
    command_topic: "cmnd/sonoff02/Backlog"
 #       command_topic: "cmnd/sonoff01/power"
#    state_topic: "stat/sonoff01/POWER"
    name: "Tenda"
    qos: 0
    retain: true
    payload_open: "power1 on"
    payload_close: "power2 on"
    payload_stop: "power1 off;power2 off"
    state_open: "ON"
    state_closed: "OFF"
    optimistic: false
    value_template: "
    {% if value_json.POWER1 == 'OFF' and value_json.POWER2 == 'OFF' %} 50
    {% elif value_json.POWER1 == 'OFF' %} 100
    {% elif value_json.POWER2 == 'ON' %} 0
    {% endif %} "
2

on automation.yaml i resolve with a open --> delay --> stop

- alias: open cover for 30 seconds
  hide_entity: True
  trigger:
    platform: time
    at: '10:23:00'
  action:
    - service: cover.open_cover
      entity_id: cover.tenda
    - delay: 00:00:30
    - service: cover.stop_cover
      entity_id: cover.tenda

but i don’t know how to set a similar things for the manual command via cover. My needs is that if i click on the open button it remain triggered for a specific time and then goes to stop