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Aaron Harper, 02/02/2013 10:40 pm
EPS Detailed Design¶
Introduction¶
While the preliminary design is nearly a complete detailed design, the PCB design needs to be completed before assembly can begin. This will be completed while parts are on order, as some have a 2-3 week lead time in the quantities required.
Design Criteria Review¶
- EPSRR 1.1 The EPS board uses a Texas Instruments MSP430 microcontroller to measure and store the sensor data
- EPSRR 1.2 the EPS board is made from components which are rated beyond the specification as listed, and the system will operate without direct intervention by an operator.
- EPSRR 2.1 The EPS board is designed in such a way that it may be installed by any person with solar power or electrical wiring experience.
- EPSRR 2.2 The EPS board will have screw holes to mount the board using #10 screws. Alternatively, a DIN rail clip may be used.
- EPSRR 2.3 The EPS board can draw it's power from either monitored load or from another 6-30VDC source.
- EPSRR 3.1 The EPS board shall measure predefined parameters.
- EPSRR 3.1.1 The EPS board measures the ambient temperature in the enclosure using a sensor on the board.
- EPSRR 3.1.2 The EPS board measures voltages of two separate circuits directly with a chip that has built in isolation.
- EPSRR 3.1.3 The EPS board limits the input voltage to the sensor to safe levels using a zener and current limiter.
- EPSRR 3.1.4 The EPS board measures the current of two separate circuits using a directly with a chip that has built in isolation.
- EPSRR 3.2 The EPS board transmits measurement data or fault conditions to the server using a MAC chip with full TCP/IP stack.
- EPSRR 3.2.1 The EPS board will transmit measurement data on demand (web page request).
- EPSRR 3.2.2 The EPS board will be capable of transmitting measurement data on a schedule (FTP or email).
- EPSRR 4.1 The EPS board consumes minimal power. Design maximum is 24mW.
- EPSRR 4.2 See EPSRR 2.3.
- EPSRR 4.3 The EPS board meets all criteria in this area, having a tolerance for massive overvoltage and 12 bit accuracy.
- EPSRR 4.4 The EPS board measures temperature within from -20 to 85C with 12 bit accuracy.
- EPSRR 4.5 The EPS board meets all criteria in this area, having a tolerance for massive overcurrent and 12 bit accuracy.
- EPSRR 4.6 The EPS board meets all criteria in this area, having a MAC controller IC with a fully functional TCP/IP stack and Ethernet Jack with Magnetics.
- EPSRR 6.1 The EPS board is read using standard web protocols which are standardized across all platforms.
- EPSRR 6.2 The EPS board uses standardized connections including Screw terminals and Ethernet.
- EPSRR 8.1 The EPS board is optimized for ease of production.
- EPSRR 8.2 See ESPRR 8.1.
- EPSRR 9.2 The production units appear to cost around $60.00 in parts.
- EPSRR 11.4 Attention has been paid into the durability of the design to keep waste to an absolute minimum.
Block Diagram¶
Schematic¶
Bill Of Materials¶
| Schematic | Description | Package |
|---|---|---|
| C1 | 68uF Capacitor | SMD |
| C2 | 120uF Capacitor | Axial |
| Cf1 | 1uF capacitor | SMD |
| Cf2 | 1uF capacitor | SMD |
| D1 | 1N5817 Schottky diode | SMD |
| L1 | 100uH Inductor | SMD |
| Ra1 | 47k Ohm .25W Resistor | SMD |
| Rb1 | 47k Ohm .25W Resistor | SMD |
| Rb2 | 47k Ohm .25W Resistor | SMD |
| Rf1 | 4.7 Ohm .25W resistor | SMD |
| Rf2 | 4.7 Ohm .25W resistor | SMD |
| Rf3 | 4.7 Ohm .25W resistor | SMD |
| Rf4 | 4.7 Ohm .25W resistor | SMD |
| RL1 | 180 Ohm .5W resistor | SMD |
| RL2 | 180 Ohm .5W resistor | SMD |
| Rs1 | 068 Ohm 10W resistor | Axial |
| Rs2 | 068 Ohm 10W resistor | Axial |
| U1 | LM2594M-3.3/NOPB Voltage regulator | SSOP-8 |
| U2 | TMP102 Temp sensor (I2C) | SSOP-6 |
| U3 | INA226 Current and voltage sensor | SSOP-10 |
| U4 | INA226 Current and voltage sensor | SSOP-10 |
| 3 position jumper block | Std | |
| 5mm barrel jack, 2.1mm center pole | Std | |
| 8 position screw terminals | Std | |
| Populated Ethernet Booster Pack (MSP430 MCU) | Board | |
| EPS PC board | Board |
Budget¶
| Schematic | Description | Prototype Cost | Production Cost |
|---|---|---|---|
| C1 | 68uF Capacitor | $.49 | $1.15 |
| C2 | 120uF Capacitor | $0.62 | $0.62 |
| Cf1 | 1uF capacitor | $0.14 | $1.15 |
| Cf2 | 1uF capacitor | $0.14 | $1.15 |
| D1 | 1N5817 Schottky diode | $0.27 | $0.19 |
| L1 | 100uH Inductor | $0.18 | $0.09 |
| Ra1 | 47k Ohm .25W Resistor | $0.37 | $0.03 |
| Rb1 | 47k Ohm .25W Resistor | $0.37 | $0.03 |
| Rb2 | 47k Ohm .25W Resistor | $0.37 | $0.03 |
| Rf1 | 4.7 Ohm .25W resistor | $0.37 | $0.03 |
| Rf2 | 4.7 Ohm .25W resistor | $0.37 | $0.03 |
| Rf3 | 4.7 Ohm .25W resistor | $0.37 | $0.03 |
| Rf4 | 4.7 Ohm .25W resistor | $0.37 | $0.03 |
| RL1 | 180 Ohm .5W resistor | $0.37 | $0.03 |
| RL2 | 180 Ohm .5W resistor | $0.37 | $0.03 |
| Rs1 | 068 Ohm 10W resistor | $2.14 | $2.14 |
| Rs2 | 068 Ohm 10W resistor | $2.14 | $2.14 |
| U1 | LM2594M-3.3/NOPB Voltage regulator | $2.70 | $2.70 |
| U2 | TMP102 Temp sensor (I2C) | $5.95 | $1.69 |
| U3 | INA226 Current and voltage sensor | $6.33 | $3.38 |
| U4 | INA226 Current and voltage sensor | $6.33 | $3.38 |
| 3 position jumper block | $.22 | $.13 | |
| 5mm barrel jack, 2.1mm center pole | $4.95 | $1.12 | |
| 8 position screw terminals | $2.45 | $2.45 | |
| Populated Ethernet Booster Pack (MSP430 MCU) | $25.00 | $25.00 | |
| EPS PC board (in qty. 10) | $0.00 | $12.00 | |
| Subtotal | $58.21 | $60.75 | |
| Labor | $1762.50 | $135.52 | |
| TOTAL | $1820.71 | $196.27 |
Note: this budget reflects 8 hours of PCB layout which will be complete by 25 FEB 2013
