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USB-SOLAR
 

 

 

USB-SOLAR

 
 
USB-SOLAR can charge USB devices such as mobile phones, IPod, GPS devices etc, from either a Lipoly battery or a solar cell. There are four modes of operation:
  • Use solar cell to charge SuperCaps, which in turn are used to power USB +5V
  • Use solar cell to charge LiPoly battery, which can then be used to power USB +5V
  • Use PC USB to charge LiPoly battery, which can then be used to power USB +5V
  • Use external +5V supply to charge LiPoly battery, which can then be used to power USB +5V

 

Charge Source Super Caps Description
Solar Yes Solar cell can be connected to either J2 pin-6, or via USB-PWR adapter to miniUSB (J6). Can be used with or without LiPoly battery. If using with battery place jumper between J1-2 and J1-3. If NOT using battery then place jumper between J1-1 and J1-2.
USB Not required Connect USB to miniUSB (J6).
Ext +5V Not required External +5V can be connected to either J2 pin-6, or via USB-PWR adapter to miniUSB (J6). External supply should be capable of supplying 5V @ 500mA.
USB and Solar Yes Connect USB to miniUSB (J6), and solar to J2 pin-6. Battery will charge from both sources.
Ext +5V and Solar Yes Connect Ext +5V via USB-PWR adapter to miniUSB (J6), and solar cell to J2 pin-6. Battery will charge from both sources.

Table (1) Charging power sources

 

Lithium Polymer Battery

3.7V LiPoly batteries available from SparkFun plug directly into J7. The battery should be capable of supplying 750mA if you plan on charging USB devices at 500mA. Also it should be capable of being charged at 500mA, although you can change resistor R24 to alter the charging current. Current drain during standby is less than 1mA.

Name

Pin Number

Description

V_BATT J7-1 + Supply. Polymer Lithium Ion Battery positive supply. Nominal 3.7V. Current drain 750mA max, <1mA during standby. Charge current 500mA max.
GND J7-2 - Supply. Polymer Lithium Ion Battery negative supply

Table (2) Battery Connector

 

Solar Cell

Solar cells available from SparkFun plug into the miniUSB (J6) via USB-PWR adapter. If the solar cell has an open circuit voltage greater than 5.1V, then the short circuit current should be less than 300mA, or you risk burning out the zener diode D1. Alternatively you can change the zener for a part with a higher power rating.

 

Power Switch

The V_USB output voltage is available at USB connector J4 and also at J2 pin-5. The voltage output can be switched on and off using momentary action switch SW1, or by external switch connected between J2 pin-1 and GND (JP8)

 

Bicolor LED (D2)

The Bicolor LED indicates state of V_USB output voltage and battery charging state.

Red LED State V_USB Output Voltage
Off 0V
Blinking +5V
Steady Reserved for future use
Green LED State Battery Charging State
Off No battery, or no charging supply
Blinking Battery charging
Steady Battery charging complete

Table (3) Bicolor LED States

Microcontroller

A SiliconLabs C8051F330 microcontroller, controls the power supplies and reports status. External systems can communicate with the microcontroller using I2C or logic level RS-232 signals connected to J2-2 and J2-3. Four unused I/O pins are available to the user at JP4, JP5, JP6, and JP7. You can use the C2DBG port to run and debug your own custom program. You will need C2DBG-ADPT to connect the SiLabs USB Debug Adapter to the 3-pin J5 connector.

Name

Pin Number

Description

C2D J5-1 C2DBG Data
GND J5-2 Ground
C2CK J5-3 C2DBG Clock

Table (4) C8051 Debug Connector

 

Host System Connector

There is provision for an external host to utilize USB-SOLAR as a smart battery. If you have a system that uses a single +5V supply, then you can simply connect your +5V supply to V_USB, and then use V_CHARGE to power your system. The connector can also be used as an alternative connection point for a solar cell (V_CHARGE), especially if you wish to retain the miniUSB for USB charging, and thus have a dual charge source system. Wires can either be inserted directly into the board, or you can use a 6-pin or 7-pin 0.1" pitch connector. Eg Molex 7pos header 22-27-2071 (Digikey WM4116), Molex 7pos housing 22-01-3077 (Digikey WM2005), Molex crimp terminal 08-50-0113 (Digikey WM1114CT). There is the possibility to strip a lot of components if using the USB-SOLAR as a smart battery controller. ie J6, J4, JP2, D2, U9, C1, C2, C71, C72, R17, R18, R19, R20, R13, R21

 

 

Name

Pin Number

Description

GND

JP8

Ground. Positioned next to J2-1, so J2 can be stuffed with 7-pin 0.1" pitch connector, and this ground can be used in conjunction with J2-1.

PWR_BUTTON

J2-1

Connected in parallel with SW1. Pulled up to +3.3V. Momentarily short to ground to enable or disable V_USB.

BATT_DATA

J2-2

Reserved for I2C SDA or UART TXD. Pulled up to +3.3V

BATT_CLK

J2-3

Reserved for I2C SCL or UART_RXD. Pulled up to +3.3V

GND

J2-4

Ground

V_USB

J2-5

Output supply, +5V @ 500mA

V_CHARGE

J2-6

Input supply. Connect to solar cell or +5V 500mA power supply

 

Table (5) Host System Connector

 

Jumper Configuration

The power source for the V_USB output voltage must be selected by jumper placement. If using battery place jumper between J1-2 and J1-3. If NOT using battery then place jumper between J1-1 and J1-2.

The state of USB data lines connected to device to be charged is controlled by JP2. However, it seems that jumper JP2 can be left in, and all devices tested so far appear to happy with this setting. The conclusion being that R17 and R19 could probably be removed from the board.

 

Case

Can be used with Serpac 031i,BK (Digikey SR031-IB-ND). The two PCB mounting holes align with the mounting bosses on both the lid, and the base of the box. Mounting on the lid tends to work better, as the bosses are shorter, and this leaves  more room in the case for the battery and Super caps.
 

 


 

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Last modified: 07/12/11