Motion Control Sure Step Stepping System Do-more PLC Programming (3 of 5) from AutomationDirect

Using the Do-more Designer programming software is very straight forward and makes quick work out of developing a project. Let's take a look! The first couple of rungs in our ladder logic are used for the Auto Cycle logic. Cycle Start and Stop push button, along with an Auto/Manual selector switch shown here are programmed into the C-more Touch Panel. With the Auto Cycle selected, we can press the Cycle Start PB, and internal Auto_Cycle control relay C10 will be locked in. The Cycle_Not_Comp control relay circuit is used to allow an index cycle to complete. This is accomplished by monitoring stepper motor is moving output signal from the drive. If taken out of Auto_Cycle, C11 will stay locked in until the Motor_in_Motion X38 signal opens. As seen in the next two instructions, the Laser Distance Sensors 4-20 mA signal, that is wired into an analog input module with a 0 to 4095 value, is scaled to read as 1.18 to 3.15 inches. With no part loaded in the rotary disk position 1, the Laser Distance sensor will indicate a distance of approximately 3.15 inches. The part when loaded will be seen as a distance of greater than 2.85 inches, but not more than 2.45 inches. The instructions shown here take the 9-bit output from the 360 degree absolute encoder and converts it to read as 1 to 360 degrees of rotation. The first step is to set up the 9 inputs, X8 thru X16, into a one word value. This is accomplished with the INITialize instruction. The output from the absolute encoder is Gray Code, and is converted to an integer value using the GRAY instruction. There is a fixed offset value of 76 that is associated with the 360 degree encoder, so a MATH instruction is used to remove the offset value. Since our application calls for the degrees to read 1 to 360, as the rotary disk moves in a counter clockwise direction, a SCALE instruction is used to reverse and change the reading. The SETUP SERial port instruction is used to initialize the Do-mores CPU serial port. To communicate to the SureStep advanced drive, the serial port is set as follows: Baud Rate: 9600 Data Bits: 8 Step Bits: 1 Parity: None Transmit Control: Unconditional RTS Control: Follows Transmitter The two rungs shown here control the Rotary Index Tables indexing function. The TMR timer shown is used to slightly delay the next index to allow the part that is loading to settle into position. The Auto_Index_RIT internal relay C12 logic becomes true when all of the conditions are met. The requirements are that the cycle is not complete, the settle timer has timed out, the part is loaded, and the steel/brass marble reject cycles are not in process. Shown next is the logic that communicates the ASCII commands of the Serial Command Language from the Do-mores CPU serial port to the SureStep advanced drivers serial port. This is our index move. The rotary disk has eight positions with a pocket to accept a part at each position. The positions are separated by 45 degrees. The stepper drive is set up to produce 36,000 steps per revolution, therefore it will take 4,500 steps to move 45 degrees. The drives acceleration, deceleration, and velocity rates are part of the ASCII string that is sent. Each SCL command is separated by a carriage return shown in ASCII as?$0D. The move command for our index is a Feed to Length type of move. The index can be executed in Auto Cycle and it can also be done in Manual Mode with the selector switch and push button on the C-more Touch Panel. Shown here is the simple logic that is used to allow the rotary disk to be jogged one degree at a time in the counter clockwise direction. The system needs to be selected in Manual Mode by the Auto_Manual selector switch on the C-more Touch Panel. Press the 1 Deg CCW push button on C-more to execute. The SCL commands are basically the same sequence that are used for the index move as described on the previous rung. One degree of movement requires 100 steps. Like the previous rung to jog the rotary disk one degree counter clockwise in manual mode, here is the logic to jog the rotary disk one degree clockwise. Shown here is the logic for the detection and rejection of any steel marbles that come through the Rotary Index Table. The steel marbles are detected at position 2 of the rotary disk by an inductive proximity. A shift register, SR instruction, is used to keep track of any steel marble reject. In our situation, the steel marble is rejected at position 3. The reject is handled by a pneumatic slide cylinder that retracts a gate, allowing the steel marble to fall through a tube into a bin. If a reject is indicated by the Shift Register bit C65, then the solenoid valve, Y0 output, is energized to open the reject gate. Magnetic sensors on the slide cylinder are used to sequence the operation. As seen here, this is the logic for the brass marble detection and rejection function. It operates the same as what was just described for the steel marble detection and rejection logic. The logic to trigger the color sensor to take a reading is very simple. DC output Y2 is used to actuate a solid state relay that is used as a signal isolator between the 24 VDC PLC output and the 5 VDC TTL level input to the color sensor. The actual reading takes place on the falling edge of the trigger signal. In an Auto Cycle, the color sensor reading occurs when the stepper motor has stopped its motion. A manual reading can be called for from a push button on the C-more Touch Panel. Because the color sensor takes a reading at Position 5 on the rotary disk, three Shift Registers are used to keep track of the color senors reading shown here as rungs 20, 21, & 22. The readings are decoded and displayed on the C-more Touch Panel three positions later, so at Position 8 we see the color exiting. For example, bit 0 starts at C216, but is decoded at C218. The logic to decode the three bits is shown on the next slide. This is the logic to decode the three bits from the color sensor that indicate the color reading from Position 5, but indicated at the exit from the Rotary Index Table from position 8. The color exiting is indicated on the C-more Touch Panel. Here are some links to additional information on the Do-more PLC that may be of benefit. Look for the other videos in this series. Thank you for watching.