h1. EPS Detailed Design

{{toc}}

h3. 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.  

h3. 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.

h3. Block Diagram

!Block_Diagram.png!

h3. Schematic 

!Schematic_1.png!

h3. 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 |

h3. 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