1) Wiring and Connectors/PC 104 Enclosure

ELECTRICAL

The following sections

The subsystem decomposition of our design concepts will be presented as follows in the subsequent pages of this document:

2) Power

3) Communication/User Interface

4) Coordinate Storage/Software

5) Accessories:

1) Cables and Connectors:

Overview

Wiring is one of the most critical phases of design because the complete functionality of the platform depends on it. Proper wiring and connections within the platform will ensure equipment protection and safety. In determining which concepts to choose, the following had to be considered: safety, regulation, ability to meet specification, modularity, robustness, and adaptability. Due to the similarities in the electronics of the 100kg and 10 kg platforms, both teams decided to combine resources and adopt the same wiring and connector concepts. The only differences will be the difference in the wire gauges connected to the motor modules due to different current consumption needs.

Data and power cabling both need to be properly designed in order to accommodate the required needs of all the subsystems. A main objective in choosing the wires and connectors is to minimize power and data loss which can be obtained by proper installation and good understanding of the constraints and capabilities of the connectors and wires. The wire sizes were chosen with regard to the platform power needs. 16 AWG wires were chosen for data cabling due to the low power consumption of the electronic components. 10 AWG wires were chosen for power cabling. For the 100kg robotic platform team, the current consumption for the motor module is as high as 27 Amps with a spike value of up to 87 Amps, which requires the use of 7 AWG wire. Due to price and availability issues, 10 AWG wires are being used. This can lead to safety concerns due to the low current handling capability of the 10 AWG wires.

Due to budget constraints, shielded color coding wiring design will not be adopted. Although it will allow ease in understanding the wiring design, other methods such as labeling will have to be adopted instead. Corrugated tubing might be considered during the future final stages of the project to add more robustness and organization to the wires. Choosing the connectors depended on the modules which were provided by the other teams on the Vehicle Systems Technology Track. Other teams, such as the data acquisition, motor control, and motor module teams has incorporated connectors into their design. The main concern is to be able to connect those modules in a safe and reliable manor.

Specifications:

NEC Standards for Color Coding and Shielded Wires

• Black – Negative

• Red – Positive

• Green - Ground

4 Pin Molex

· 600 V rating

· Temperature: -40 to 105 C

· ROHS compliant

· 4 circuit Brass Connector

Figure E1.1: 4 Pin Molex

4 Pin ATX

· Pitch 4.2 mm

· Current up to 9A

· Contact Resistance: 10m ohm

· Voltage: 600 V

· Temperature: -40 t 105 C

Figure E1.2: 4 Pin ATX

10-16 AWG

• Temperature: -40 to 80 C

• Voltage Rating: 1000 V

• Strand: 26/30

• Length: 100 ft

Figure E1.3: Wire

DB-9 Connector

• 9 Pin

• 1.15 mm Drill

• Minimum PCB Tin Plating to be 0.003 mm thick over 0.002 +- 0.001 thick copper

Figure E1.4: DB-9 Connector

LED Drive

· Drives 6 LEDs from 2.6 V to 5.5 V (Li-Ion) input supply

· 1×/1.5×/2× fractional charge pump to maximize power efficiency

· 1% max LED current matching

· Up to 88% power efficiency over Li-Ion range

· 2.5 to 5 mA current supply

· Shutdown Current 5 uA

Spade Screw terminals

· Copper Terminals

· 10-12 AWG wires

· Stud Size 8

Figure E1.5: Spade Screw Terminal

Top Level Electrical Subsystem Wiring Block Diagram:

Figure E1.6: Block Diagram

Detailed Wiring Diagram

Figure E1.7: Detailed Wiring Diagram

Metric conversion: 1 inch = 0.0254 m

Calculations

AWG / Diameter / Turns of wire / Area / Current Rating / Max Current Rating
(mm) / (per cm) / (mm²) / (A) / (A)
6 / 4.115 / 2.43 / 13.3 / 37 / 101
7 / 3.665 / 2.73 / 10.5 / 30 / 89
8 / 3.264 / 3.06 / 8.37 / 24 / 73
9 / 2.906 / 3.44 / 6.63 / 19 / 64
10 / 2.588 / 3.86 / 5.26 / 15 / 55
11 / 2.305 / 4.34 / 4.17 / 12 / 47
12 / 2.053 / 4.87 / 3.31 / 9.3 / 41
13 / 1.828 / 5.47 / 2.62 / 7.4 / 35
14 / 1.628 / 6.14 / 2.08 / 5.9 / 32
15 / 1.45 / 6.89 / 1.65 / 4.7 / 28
16 / 1.291 / 7.75 / 1.31 / 3.7 / 22

Table E.1.1: Wire Gauge Current Specifications(NEC Standards 2005)

Note: The cross-section area is also roughly proportional to the maximum current that a wire can carry safely.

With respect to the 100Kg Robotic Platform, the maximum current intake is 27 A. For this reason 7-8 AWG wire would be appropriate. Instead 10 AWG is being adopted due to extremely high price of 7 AWG wires.

For the 10Kg Robotic Platform, the maximum current intake will be 4 A, and hence, the 10 AWG wire can be used without any problem.

Cost:

Table E1.2: Bill of Materials

Note: The budget might drop below $ 81.98 if samples are available. Also, if the 16 AWG and the 10 AWG are not available from the RIT resources, then the budget will increase $ 255.00

The lead time on the all the components is a maximum of 14 days; this was determined by contacting each vendor. The time required for the most economical shipping method was calculated as the worst case lead time.

Risk ID / Corresponding
Spec #’s(10kg) / Corresponding
Spec #’s(100kg) / Description of Risk / Probability
(0 – 1) / Impact
(low, med, high) / Importance
(1-4) / Classification / Mitigation Strategy
1 / NA / 1.1,1.5 / Using 10 AWG wires instead of 7 AWG / 0.9 / med / 3 / Technical / Make sure over current protection works properly
2 / 18,19,62 / 1.1,1.5,2.5,5.1,8.2,8.4 / Not using color coded wires due to tight budget / 0.5 / Low / 1 / Safety/Budget / Using wiring labels
3 / 12 / 1.1,1.5 / Improper grounding / 0.1 / High / 4 / Safety / Double check wiring and connections before powering platform
4 / 11 / 1.1,1.5 / Plugging in power and ground backwards / 0.1 / High / 3.5 / Safety / Have clearly labeled warning signs
5 / 12 / 1.1,1.5 / Shorting/Breaking of wires / 0.1 / Med / 3.5 / Safety
Technical / Proper installation with corrugated tubing
6 / 62 / 5.1,8.1,8.4,11.1 / Not being able to get wires for free. / 0.5 / Med / 3 / Budget / Avoid color coding and use 1 color.
Adopt wire labeling.
Contact additional suppliers for donations/samples
7 / 12,18,19,62 / 1.1,1.5,5.1,8.1,8.2,6.1 / Not using corrugated tubing / 0.5 / Low / 1 / Safety/Budget / Using wiring labels
Use shrink tubing
8 / 46 / 7.2, 7.4 / Sensor mount cannot accommodate sensor / 0.5 / low / 2 / Technical / Make sensor mounting procedure as generic as possible
9 / Enclosure Overheat / PLEASE FILL OUT NATHAN
10 / Cannot Afford enclosure / PLEASE FILL OUT NATHAN

Risk Assessment

Safety

Overall safety of the robotic platform is a major concern of this project. The order of precedence of safety is as follows; protect the user first, then the environment, and lastly the robotic platform itself. The major concern in choosing the wiring concepts and connectors is that the user can clearly understand the wiring layout. This will be done by using wire labeling. This will prevent the user from getting shocked or shorting out any electronic components. The sizes of wires were chosen based on the worst case current handling requirements which include the initial spikes in currents from the motor module startups. Table E 1.1 shows the wire gauge current specifications. From that table, the use of 16 AWG and 10 AWG wires was determined as the wires to be used to connect the electronic components and power to the platform.

Reference:

Enclosure for battery

http://www.hammondmfg.com/1455ZT.htm

Enclosure for PC 104

http://www.diamondsystems.com/products/cantainer#kc