Introduction to Handshaking Communication Manufacturing Costs CIM Cost of Manufacturing Introduction to Handshaking Communication Project Lead The Way, Inc. Copyright 2008

Table of Contents Definition Signal Compatibility Components: Optical Isolator Relays Resistors Breadboards Communications: Lynx to Lynx Lynx to VEX VEX to Lynx VEX to VEX Lynx to Fischertechnik Fischertechnik to Lynx Fischertechnik to Fischertechnik

Handshaking Handshaking is the process of communication that occurs between a robot and another piece of equipment in a workcell.

Handshaking This is a very simple form of communication. A signal is sent from one machine to the robot or from the robot to a machine. Can also be between two robots or two machines. This signal is a simple “on” or “off”, in digital terms, a 1 (on) or a 0 (off). Did you ever notice that the symbol for an on/off switch is a “1” inside of a “0”? Check the computer you’re sitting at!

What is it used for? When a part feeder is empty. When a part is available for pick up or delivery. When an operation is completed. Communication between devices in a work cell are very important. A robot needs to know when to pick up a part, drop it off, or perform an operation. How many different forms of handshaking could be performed in the cell above?

Signal Compatibility When two machines talk, signals should be isolated to protect the machines from incompatible signals. Optical Isolators and Relays are used to do this. Some devices we use have a 7.2V signal, some have 5V signals, and still others 3.3V. What would happen if you sent a 3.3V signal to a machine looking for a 7.2V signal? Would it see it as an “on”? Even worse, suppose you send a 7.2V signal to a device expecting a 3.3V signal. This could damage the equipment!

Components: Optical Isolators An Optical Isolator sends a signal as a light pulse from an LED (1 & 2) on the input side. The output side of the circuit “sees” the light and sends the signal (4 & 6). Optical Isolators use a small IR LED connected to the INPUT side of the circuit. When voltage is applied, the LED shines on an IR sensor on the OUTPUT side. This sends the “on” signal with no voltage. It just completes the circuit.

Components: Relays A relay contains a coil of wire on the input side. (A & B) When power is sent to this coil, it creates a magnetic field. This causes a connection on the output side. (C & D) A relay is nothing more than a magnet and a reed switch. When the magnet is energized, it closes the switch.

Components: Resistor A resistor is used to limit the amount of current to another component like the optical isolator. A resistor is a component that resists electrical current. We use it to limit the current going to the optical isolator.

Components: Breadboards A breadboard is used to create a simple circuit without soldering. Keep wires as short as possible. Use as few wires as possible. On a breadboard, the five holes in a “row” above are connected internally, and the “columns” are not. Components must always go across the “gap” in the middle, or they would be short-circuited. The columns on either side of the board above are connected vertically, and are called bus bars. These aren’t used for handshaking. Info and picture from DE ppt Breadboard[1].ppt

Lynxmotion Robot to Lynxmotion Robot Communication Example: When two robots have to perform a task at the same time. or When one robot needs to wait for another to complete a task.

Lynx to Lynx Communication In the example above, the Lynxmotion robotic arm on the left is using pin 15 as an output. Any output, 8-15 can be used for this purpose. Be sure to have the black wire, or ground, always facing the outer edge of the SSC-32 board. The Lynxmotion robotic arm on the right waits for this signal on Input pin D in the diagram above. Depending what you want to do, pins A-D can be used for this. The black wire still has to go to an output on the right side to pick up the ground to complete the circuit. See the curriculum to learn how to modify a servo extension to make this connection.

Lynx to Lynx Schematic 220Ω Ground Black NC 1 2 3 6 5 4 A C B E Signal Yellow/White 4N25 Optoisolator Signal Yellow/White This is an example wiring diagram. Note what happens internally on the optical isolator. It’s the same as a VEX or Fischertechnik light sensor! Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot!

VEX Machine to VEX Machine Communication Example: When one machine completes an operation in a sequence, it can let the next one know when it is done and it is safe to start. In this example, a grinder and a drill press made out of VEX components are used.

VEX to VEX Communication In the diagram above, the VEX Cortex on the left outputs a signal from Digital I/O 1 configured as a digital output in RobotC. The Cortex on the right is using Digital I/O 1 configured as a digital input in RobotC. Any of the Digital I/O ports can be used. NEVER USE A MOTOR PORT AS AN OUTPUT FOR COMMUNICATIONS.

VEX to VEX Schematic Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot! Arrows in the diagram above show direction of communication. When using a VEX component to communicate with another VEX component the signal to the second component gets inverted due to the optical isolator, so keep this in mind when programming in RobotC.

Lynx Robot to VEX Machine Communication Example: When a robot places a part on a conveyor, it can tell the conveyor when it is done. Machines can be simulated with VEX components and can easily communicate with your Lynxmotion robotic arm.

Lynx to VEX Communication In the example above, the Lynxmotion robotic arm on the left is using pin 15 as an output in this diagram. Be sure to have the black wire, or ground, always facing the outer edge of the SSC-32 board. Any output 8-15 not already used can be used for this. The VEX Cortex waits for the signal on Digital I/O pin 1. Any Digital I/O 1-12 not already in use can be used. Note that the black wire always goes to the outside edge of the Cortex when using the Digital I/O ports.

Lynxmotion to VEX Schematic Example When a robot places a part on a conveyor, it can tell the conveyor when it is done. The red arrows denote direction of communication. Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot!

VEX Machine to Lynxmotion Robot Communication Example: When a machine is performing an operation, it can tell the robot when the operation is complete and it is safe to get the part. Example: When a machine completes an operation, it can tell the robot that it is finished, and that it may come and pick up the part. The example above might be a buffer, or a grinder.

VEX To Lynx Communication In this example, the VEX Cortex outputs a signal to a Lynxmotion Robotic arm. The Digital I/O 1 port is being used and is configured as a digital output. Digital I/O ports 1-12 can be used for this purpose. The SSC-32 on the Lynxmotion robotic arm waits for this signal on Input pin D. Depending upon what you want to do, Inputs A-D on the SSC-32 can be used for this.

VEX to Lynxmotion Schematic Arrows denote the direction of the communication. Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot! Programming is done in RobotC by configuring a digital I/O port as an Output, and then using the TurnLEDon/off to send the signal. See the example in the Teacher Notes.

Fischertechnik to Fischertechnik Communication Example: When one machine completes an operation in a sequence, it can let the next one know when it is done and it is safe to start. In this example a Fischertechnik drill press can let a conveyor know when it is done, so it can position itself to accept another part when a robot picks it up.

Fischertechnik to Fischertechnik Communication In this example, the Tx interface on the left is sending a signal from port M1. Any port M1-M4 can be used for this purpose. The Tx Interface on the right is receiving the signal on port I1. Any port I1 to I4 can be used for this purpose.

Fischertechnik to Fischertechnik Schematic Red arrows denote the direction of communication. Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot!

Lynx to Fischertechnik Communication Example: When a robot places a part on a drill press, it can tell the conveyor when it is done.

LynxMotion to Fischertechnik Communication In the diagram above, the SSC-32 of the Lynxmotion Robotic Arm is using Output Pin 15 to send a signal. Output Pins 8-15 may be used for this. Be sure to have the black wire to the outside of the SSC-32 as shown above. The TX Interface is using port I1 to receive the signal. The polarity of the wires from the relay to this port do not matter; it will work both ways.

LynxMotion to Fischertechnik Schematic Arrows denote the direction of communication. There is no polarity on wires going to the TX interface. Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot!

Fischertechnik to Lynxmotion Communication Example: When one machine completes an operation in a sequence, it can let the robot know when it is done.. In this example a Fischertechnik conveyor system can let the Lynxmotion robotic arm know when a part is in position and is ready to be picked up.

Fischertechnik to Lynxmotion Communication In this example, the Tx interface on the left is using port M1 to send a signal. Any port M1 to M4 may be used for this purpose. On the right side above, the Lynxmotion robotic arm is receiving the signal on Input port D. Depending on what you want to do, ports A-D can be used for this purpose.

Fischertechnik to Lynxmotion Schematic Red arrows denote the direction of communication. Remember to keep the wires as short as possible, and use as few wires as possible when bread boarding. This will make it much easier to troubleshoot!