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Dosing Machine PLC

Disclaimer: This project was part of Udacity's "From Wire to PLC, A Bootcamp In Industrial Automation" course. I completed this project with help from the videos in the class and my final product was ultimately checked against the solution provided.

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Link to Course: https://www.udemy.com/course/from-wire-to-plc-a-to-z-compilation/

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I took Udemy's "From Wire to PLC, A Bootcamp In Industrial Automation" course because I became very interested in automated manufacturing after working at Tesla and wanted to learn more about it. The course covered topics such as:

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  1. Basic electrical concepts and components and how they operate

  2. Traditional motor driving control circuits and modern motor driving equipment

  3. Protection components and how to choose them

  4. Wiring and cable sizing

  5. Sensors and their utilization in real projects

  6. Electrical Panel Troubleshooting

  7. Schematics drawing and design

  8. PLC programming using Ladder Logic, Structured Text, and Functional Block Diagrams

  9. Allen Bradley - RsLogix 500, RsEmulate 500 and Rslinx Training

  10. Human User Interface design and Animation

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Completion Certificate

Dosing Machine Project

Goal: Design the control logic for a dosing machine and build an animated visual to simulate the machine.

 

A dosing machine takes two materials and dispenses and mixes them according to the recipe to create a final product.

Main Components

  1. Motor 1: for feed elevator 1

  2. Motor 2: for feed elevator 2

  3. Motor 3: for spiral conveyor 1

  4. Motor 4: for spiral conveyor 2

  5. Motor 5: mixer

  6. Dosing silo 1 load cell: to measure amount of material 1

  7. Dosing silo 2 load cell: to measure amount of material 2

  8. Mixer gate valve: to oper mixer gate

dose.jpg

Example of a Dosing Machine

Motor Driving and Cabling

Motor 1 and Motor 2 (elevators)

Given criteria:

  • 3kW 380VAC 3-Phase

  • AC-3 Contactor

  • Distance from the panel: 5m

Calculations:

  • I = W/(V*0.7*1.73) = 6.5A

  • Overload at least 6.5A

  • From cable size table: 1.5mm diameter cable

Motor 3 and Motor 4 (spiral conveyors)

Given criteria:

  • 1kW 380VAC 3-Phase

  • Speed control: 1kW VFD

  • Distance from the panel: 5m

Calculations:

  • I = W/(V*0.7*1.73) = 2.2A

  • Overload not required

  • From cable size table: 1.5mm diameter cable

Total power = (3kW * 2) + (1.1kW * 2) + 5.5kW = 13.7kW

Need:

  • 60m of 1x1.5mm

  • 15m of 1x2.5mm

Motor 5 (mixer)

Given criteria:

  • 5.5kW 380VAC 3-Phase

  • Speed control: 5.5kW VFD

  • Distance from the panel: 5m

Calculations:

  • I = W/(V*0.7*1.73) = 12A

  • Overload not required

  • From cable size table: 2.5mm diameter cable

Sensors, Actuators, and Cabling

Analog Load Cells

  • Load cells have distance of 1m and 4x0.75mm shield cable type 

  • Analyzers have distance of 6m and 4x0.75mm shield cable type and run at 4-20mA

 

Current = 20mA per PLC input + internal consumption Current = (20mA + 8mA) * 2 = 56mA

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8 load cells = 8 * 1m = 8m

2 analyzers = 2 * 6m = 12m

Total: 20m of 4x0.75mm

Actuators​

table1.JPG

Current = 12mA per input + 9mA per relay coil

Current = (12mA + 9mA) * 6 = 135mA

Choosing PLC and IO

Digital Outputs (12mA each)

  1. Motor 1 (elevator 1)

  2. Motor 2 (elevator 2)

  3. Motor 3 (spiral 1)

  4. Motor 4 (spiral 2)

  5. Motor 5 (mixer)

  6. Mixer Gate

  7. Spare1

  8. Spare2

Digital Inputs (12mA each)

  1. Motor 1 (elevator 1) OVLD

  2. Motor 2 (elevator 2) OVLD

  3. Motor 3 (spiral 1) OVLD

  4. Motor 4 (spiral 2) OVLD

  5. Motor 5 (mixer) OVLD

  6. EMGC stop

  7. Spare1

  8. Spare2

Analog Outputs (12mA each)

  1. VFD1 frequency

  2. VFD2 frequency

Analog Inputs (20mA each)

  1. LoadCell analyzer 1

  2. LoadCell analyzer 2

Current = DOs + DIs + AOs + AIs + Relays + PLC Internal + VFD Internal + Analyzer

Current = (12mA * 8) + (12mA * 8) + (12mA * 2) + (20mA * 2) + (9mA * 8) + 20mA + (5mA * 3) + (8mA * 2) Current = 427mA

1A 24VDC power supply with shortcircuit protection is more than enough.

Choosing Circuit Breakers

Main Breaker

Total power = 13.7kW

Total current = 13.7kW / (380 * 0.7 * 1.73) =30A * 10 (worst case inrush current) = 300A

Cable length from power source to breaker = 10m

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Is 2.5mm enough? In other words, is voltage drop less than 3%?

Voltage drop % = (1.73 * current * cable_imp._per_meter * cable length * 100) / voltage source

Voltage drop % = (1.73 * 30 * 0.0138 * 10 * 100)/380 = 1.11% < 3% -- 2.5mm is acceptable

 

MCBs

From cable size table, max current for 2.5mm cable is 32A. Main input MCB should be rated at 32A type C to account for inrush currents.

table3.JPG

Since these are only for switching, any rating higher than the device max rating is enough.

Schematics

schem`.JPG

MCB Schematic

schem3.JPG

VFD Schematic

schem2.JPG

Motors Schematic

schem4.JPG

PLC Schematic

CodeSys Demonstration

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