This project uses relays to control a Firgelli Automations linear actuator without feedback. The relays are controlled by the MIDI Volume (Control Change number CC7) command which is read by the microcontroller and converted into one of the only 3 states of operation:
1) The Linear Actuator is stopped,
2) The Linear Actuator is extending,
3) The Linear Actuator is retracting.
Using the MIDI Volume CC7 command allows the user to automate the control of the linear actuator, either in real-time or the MIDI data can be recorded into a MIDI sequencer and then played back to repeat the sequence as required.
The MIDI Linear Actuator unit utilizes:
- An Arduino Board including a suitable pre-programmed Atmega microcontroller,
- A 2.1mm power socket, and associated LED,
- MIDI Control Change (CC7) Volume control value is used to control the Linear Actuator, but may be pre-programmed to any value,
- A 2 relay board, to extend or retract the Linear Actuator,
- A MIDI IN/OUT Board,
- A MIDI 5-pin DIN input socket,
- A MIDI 5-pin DIN output socket,
- MIDI channel is selectable via a 4-way DIP switch.
The MIDI Linear Actuator also requires:
- A 12v DC power source
Circuit Schematic:
A circuit schematic of the Arduino/MIDI board shows the Input/Output connections for both units. The relay board circuit schematic is also available.
Operation:
At power-on (or reset) the software waits for the Volume Control (CC7) Change command to approximately reach mid-position, which is signified by turning On the LED connected to Pin 13 on the Arduino board.
Now the main program reads the Volume Control (CC7) Change value and if it remains in the mid-position then both relays are Off and the Linear Actuator is stopped.
if the Volume Control (CC7) Change value increases above a certain threshold Relay 1 is switched On, (Relay 2 is Off), and the Linear Actuator starts extending. This also lights LED1 (LED2 is Off). Also the LED connected to Pin 13 on the Arduino board is now Off.
If the Volume Control (CC7) Change value decreases below a certain threshold Relay 2 is switched On, (Relay 1 is Off), and the Linear Actuator starts retracting. This also lights LED2 (LED1 is Off). Also the LED connected to Pin 13 on the Arduino board is now Off.
If the Volume Control (CC7) Change value returns to the mid-position then both relays are Off and the Linear Actuator is stopped.
For more detail: MIDI Linear Actuator
