update docker readme.

DOCKER.md

@@ -37,6 +37,61 @@ For example to use a `p300_multi` on the right add:
     OT_EMULATOR_smoothie: '{"right": {"model": "p300_multi"}}'
 ```
 
+
+### Adding more emulators
+
+#### Magdeck
+
+To add a second mag deck emulator make a copy of the existing `magdeck` section and change the key and `serial_number`. 
+
+For example this adds a `magdeck` with the serial number `magdeck2`:
+```
+ magdeck2:
+    build: .
+    command: python3 -m opentrons.hardware_control.emulation.scripts.run_module_emulator magdeck emulator
+    links:
+      - 'emulator'
+    depends_on:
+      - 'emulator'
+    environment:
+      OT_EMULATOR_magdeck: '{"serial_number": "magdeck2", "model":"mag_deck_v20", "version":"2.0.0"}'
+```
+
+#### Tempdeck
+
+To add a second temp deck emulator make a copy of the existing `tempdeck` section and change the key and `serial_number`. 
+
+For example this adds a `tempdeck` with the serial number `tempdeck2`:
+```
+ tempdeck2:
+    build: .
+    command: python3 -m opentrons.hardware_control.emulation.scripts.run_module_emulator tempdeck emulator
+    links:
+      - 'emulator'
+    depends_on:
+      - 'emulator'
+    environment:
+      OT_EMULATOR_tempdeck: '{"serial_number": "tempdeck2", "model":"temp_deck_v20", "version":"v2.0.1", "temperature": {"starting":0.0, "degrees_per_tick": 2.0}}'
+```
+
+#### Thermocycler
+
+To add a second thermocycler emulator make a copy of the existing `thermocycler` section and change the key and `serial_number`. 
+
+For example this adds a `thermocycler` with the serial number `thermocycler2`:
+```
+ thermocycler2:
+    build: .
+    command: python3 -m opentrons.hardware_control.emulation.scripts.run_module_emulator thermocycler emulator
+    links:
+      - 'emulator'
+    depends_on:
+      - 'emulator'
+    environment:
+      OT_EMULATOR_thermocycler: '{"serial_number": "thermocycler2", "model":"v02", "version":"v1.1.0", "lid_temperature": {"starting":23.0, "degrees_per_tick": 2.0},  "plate_temperature": {"starting":23.0, "degrees_per_tick": 2.0}}'
+```
+
+
 ## Known Issues
 
 - Pipettes cannot be changed at run time.