Hard Stop
Emergency stop (Hard stop). Cuts down the power of all motors (platform and arm). Since the arm motors have no brakes, the arm can/will collapse.
Hardware
You need to buy an emergency stop button (can be bought in most electronic shops). They all function in the same way, which is a "Normally closed push-button"
Usually Emergency stop buttons have 4 pins (industrial safety regulations require the safety systems to be redundant), however, to enable hard stop in youBot you only need 2 pins. Remaining two can be shorted.
Connecting
Only Pin 1 and 2 have to be connected with an Emergency Stop Button, which is nothing else than a 'Normally closed push-button' as shown below. Pin 3 should not be connected.
As written in the documentation when Pin 1 and 2 are connected (Closed CIrcuit) youBot will function and at Open Circuit, communication or Power will be cut down, if connected as Soft Stop or Hard Stop accordingly.
