Servo Trigger
Servo Trigger
This is a basic Servo Trigger with the servos running at variable speed.
The servo can be stopped at any point in it's travel.
Features
- Six trigger input pins
- Five operating modes
- Level trigger inputs
- Edge trigger inputs
- Limit switch inputs
Trigger inputs
There are six trigger input pins that activate when shorted to ground.
The pins are labeled "Switch Inputs" on the circuit board.
A row of ground pins is provided so all that's needed is to short the pair of pins for an input.
the trigger inputs are assigned an input pin (1-6) depending on the operating mode.
The possible trigger inputs are:
- Level trigger, Move to retract (home) position while trigger is active
- Level trigger, Move to advance (deployed) position while trigger is active
- Level trigger, Run continuously (back and forth between retract and advance positions) while trigger is active
- Edge trigger, Move to retract (home) position
- Edge trigger, Move to advance (deployed) position
- Edge trigger, Half cycle
- Edge trigger, Full cycle (to retracted position)
- Edge trigger, Toggle continuous run/stop
Limit switch inputs
There are two of limit switch inputs that can be used with Level Triggers.
When limit switches are used the servo will stop when the limit switch is activated OR when the end of travel (retract or advance position) is reached.
Like the trigger inputs, the limit switch inputs are assigned an input pin (1-6) depending on the operating mode.
The limit switch inputs are:
- Retract position limit
- Advance position limit
Control Knobs
Three trimpots with knobs control these settings:
- Servo retract position
- Servo advance position
- Servo speed
Operating Modes
The input pin functions depend on the mode setting.
The 'setup' button indicates the current mode and allows a new mode to be entered.
Pressing 'setup' blinks the current mode number, then press the 'setup' button 1 to 4 times to set a new mode.
After a pause, the new mode number will blink and the setup is complete.
| Mode 1 - (default) General purpose assortment of level triggers edge triggers | ||
| Pin 1 | Level trigger | Run continuously |
| Pin 2 | Level trigger | Move to advance position |
| Pin 3 | Level trigger | Move to retract position |
| Pin 4 | Edge trigger | Full cycle (to retract position) |
| Pin 5 | Edge trigger | Half cycle |
| Pin 6 | Edge trigger | Run/stop toggle |
| Mode 2 - Level triggers with limit switches | ||
| Pin 1 | Level trigger | Run continuously |
| Pin 2 | Level trigger | Move to advance position |
| Pin 3 | Level trigger | Move to retract position |
| Pin 4 | Limit switch | Advance position limit |
| Pin 5 | Limit switch | Retract position limit |
| Pin 6 | Edge trigger | Run/stop toggle |
| Mode 3 - All edge triggers | ||
| Pin 1 | Edge trigger | Move to advance position |
| Pin 2 | Edge trigger | Move to retract position |
| Pin 3 | Edge trigger | Full cycle (to retract position) |
| Pin 4 | Edge trigger | Half cycle |
| Pin 5 | Edge trigger | Run |
| Pin 6 | Edge trigger | Stop |
| Mode 4 - Edge triggers with limit switches | ||
| Pin 1 | Edge trigger | Move to advance position |
| Pin 2 | Edge trigger | Move to retract position |
| Pin 3 | Edge trigger | Full cycle (to retract position) |
| Pin 4 | Edge trigger | Half cycle |
| Pin 5 | Limit switch | Limit switch on advance position |
| Pin 6 | Limit switch | Limit switch on retract position |
Configuration Console
Servo trigger can be plugged into a USB port and any serial terminal at 115200 baud can be used to configure more settings.
Settings that can be changed are:
- Servo pulse width range (type of servo)
- Servo speed range
Specifications
- Power supply: 5V to 6V (whatever the servo prefers)
- Dimensions: 37mm x 41mm
Optional Input Conditioning
Pads are provided on the circuit board for:
- Stronger pullup resistors (e.g. 1K)
- Filter capacitors (e.g. 100nF)
Design Documents
| Schematic Diagram | servo_trigger_schematic.pdf |
| PCB Gerbers | gerbers_OA22.zip |
| Arduino Source Code | Arduino.ino |
Parts List
| C1-C6 | 6 | 100nF typical | Noise suppression capacitor (optinal) |
| J1 | 1 | .1" 2 pin JST | Power connector |
| J2 | 1 | .1" 2x6 header | Power connector |
| J3 | 1 | .1" 1x3 header | Power connector |
| R1-R6 | 6 | 1K typical | Strong pullup resistor (optinal) |
| RV1-RV3 | 3 | 10K trimpot | Knobs |
| SW1 | 1 | small button | Tactile switch for setup |
| U1 | 1 | ESP32-C3 | Microprocessor |
| PCB | 1 | OA22 | Printed circuit board |
Build Pictures
Breadboard development
Boards from PJRC
Finished Board