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            "802": {
                "pageid": 802,
                "ns": 0,
                "title": "Reducing power consumption of a raspberry Pi",
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                        "*": "= Introduction =\n\nThe Raspberry Pi relies on a linear regulator for its 3V3 rail. This dissipates a third of the energy as heat, which is a bit of a waste, if you want to power your Pi from an battery. Our solution: Replace the linear regulator with a [http://www.bitwizard.nl/shop/power-heat/dc-dc-step-down-conv  switching regulator from our shop]. We also used another regulator for the 5V power, to test powering a Pi from a car battery.\n[[File:switcher.jpg|none|thumb|300px|alt=One of our switching regulators|One of our switching regulators]]\n\n= Initial measurements =\n\nWe tuned our benchtop power supply to 12V DC, and set the current-limit to approximately 400mA. Then we adjusted one of the switching regulators to 5V, and labelled it. We gave our Pi an SD card, and ethernet connection. We then hooked up the power to the Pi, on its GPIO header (GND on pin6, 5V on pin2). After booting, the current consumption from the benchtop supply stabilized between 190 and 200mA, which translates to a power consumption of about 2,4W.\n\n= Slicing the Pi =\n\nTo make sure the linear regulator stopped wasting power, we completely removed it from our Pi, with a hot air rework station. To do this, we grip the regulator with some metal tweezers, lift the Pi about a centimetre, and then blast the regulator with air at about 400 degrees Celsius. After a few seconds, the Pi drops to the table, and the regulator was removed:\n[[File:No_LM1117.jpg|none|thumb|300px|alt=There used to be an LM1117-33 at this spot...|There used to be an LM1117-33 at this spot...]]\n\n= Decorating the Pi =\n\nWe adjusted a second switcher to 3,3V and connected both the 5V and 3V3 switchers to the GPIO header of the Pi (with the benchtop power supply still turned off); 3V3 on pin1, 5V on pin2, GND on pin6.<br>\n[[File:2regulators.jpg|none|thumb|300px|alt=The two regulators connected to the Pi|The two regulators connected to the Pi]]\nThe Pi also got the same SD card and ethernet connection as with the initial measurements.<br>\nWe double/triple checked everything, crossed our fingers, and turned on the benchtop supply. After booting, the power consumption settled on 150mA at 12V, a 25% improvement!\n[[File:benchtop.jpg|none|thumb|300px|alt=The resulting current draw|The resulting current draw]]\n[[File:Final_setup.jpg|none|thumb|300px|alt=The final working setup|The final working setup]]\n\n= Further reduction =\nA further power reduction can be achieved by tying the 5V and 3V3 lines both to the 3.3V DCDC converter (and obviously removing the 5V one). Everything that depends on the 5V will stop working, but most of the 'pi will work. What won't work are devices depending on the 5V powersupply on the GPIO, HDMI and the USB connectors.\n\n= Conclusion =\n\nIf you're not afraid of modifying your Raspberry Pi, and want to power it from a limited power source, such as a battery or solar panel, it's well worth the trouble and cost of replacing the linear regulator by a switching one. The only downside is that the extra regulator takes up a little extra room."
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            "53": {
                "pageid": 53,
                "ns": 0,
                "title": "Relay",
                "revisions": [
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                        "*": "[[File:SPI_relay.jpg|thumb|300px|alt=The SPI_relay board|The SPI_relay board]]\n[[File:bigrelay.jpg|thumb|300px|alt=The BigRelay board| The BigRelay board]]\nThis is the documentation page for the I2C/SPI Relay and BigRelay boards. \nThe Relay board can be bought here in the [http://www.bitwizard.nl/shop/expansion-boards/relay BitWizard Shop].\nThe BigRelay board can be bought here in the [http://www.bitwizard.nl/shop/expansion-boards/bigrelay BitWizard shop].\n\n\n== Overview ==\nThe Relay board allow you to drive two relays, while the BigRelay board can drive six relays. Both of the boards have a I2C and SPI version.\n\n== Assembly instructions ==\n\nNone: the board comes fully assembled. \n\n== Protocol == \n\nTo make the relay PCB do things, you need to send things over the SPI bus to the PCB. \n\nThe general overview of the protocol is [[General_SPI_protocol|here]]. \n\nThe specific commands for the relay PCB are explained on the page about the spi_dio board, as the two boards share the same protocol: [[DIO_protocol]] . The address of the BigRelay was incorrectly documented at first. The correct address is 0x9c. \n\nFor Arduino, a sample PDE is available, called ardemo_lcd.pde, also at [http://www.bitwizard.nl/software the BitWizard software download directory] .\n\nThis is a demo to send things using SPI to the lcd board. The SPI routines there are applicable for the dio and relay boards as well.\n\n== Jumper settings ==\n\nThe Bigrelay has a jumper on the right side of the board. It is usually marked \"SV1\". The pinout is as follows:\n\n* 3 - +5V from SPI/I2C (marked \"5V\")\n* 2 - 5V for the relays (marked \"aux 5V\")\n* 1 - GND (marked GND)\n\nThis allows you to use the SPI/I2C  5V by installing a jumper on 2-3, or use an external powersupply by connecting the powersupply GND to pin 1 and the 5V from the powersupply to pin 2.\n\n== Additional Considerations ==\n\nEach relay draws about 70mA. This means that if you have the bigrelay board, and turn on all six relays, the current draw will amount to about 400mA. If you have the board connected to a Raspberry Pi, this might stress your polyfuse on the 5V line, and/or exceed the capabilities of your powersupply. You can supply extra 5V power on the 5V lines of other connectors on the board. For example, if you have the SPI version, you can mount one of the I2C connectors and provide GND and 5V on pin 1 and 4 respectively. \n\nNote that your extra powersupply is likely to start powering the Raspberry Pi a bit as well. (Due to the voltage drop over the polyfuse in the Raspberry Pi, the 5V on the relay board is likely to be a bit higher than that what ends up on the Pi itself.) You could consider powering the whole system through this extra powersupply, but be careful, the polyfuse on the Pi is now circumvented.\n\nOn the other hand, on the newer bigrelay boards, you can provide the power for the relays on SV1 as described above.\n\n== Default operation ==\n\nBy default the relays will start out in the \"off\" position. (i.e. a connection between the common and the \"normally closed\" will be present).\n\n== Power Consumption ==\n\nEach relay typically consumes about 55mA. Max 70mA. So for a bigrelay with all relays \"on\" you need to arrange for about 400mA of power. The board uses about 8mA when idle (typ).\n\n== Pinout ==\n\nFor the SPI connector see: [[SPI_connector_pinout]]. \n\nFor the I2C connector see: [[I2C_connector_pinout]]. \n\n{| border=1\n! pin !! function !! remark\n|-\n| 1 || NO 1 || Normally open contact for relay 1\n|-\n| 2 || C 1 || center connection for relay 1\n|-  \n| 3 || NC 1 || normally closed contact for relay 1\n|-\n| 4 || NO 2 || Normally open contact for relay 2\n|-\n| 5 || C 2 || center connection for relay 2\n|-  \n| 6 || NC 2 || normally closed contact for relay 2\n|-\n| colspan=\"3\"| Only for BigRelay:\n|-\n| 7 || NO  || Normally open contact for relay 3\n|-\n| 8 || C  || center connection for relay 3\n|-  \n| 9 || NC  || normally closed contact for relay 3\n|-\n| 10 || NO  || Normally open contact for relay 4\n|-\n| 11 || C  || center connection for relay 4\n|-  \n| 12 || NC  || normally closed contact for relay 4\n|-\n| 13 || NO  || Normally open contact for relay 5\n|-\n| 14 || C  || center connection for relay 5\n|-  \n| 15 || NC  || normally closed contact for relay 5\n|-\n| 16 || NO  || Normally open contact for relay 6\n|-\n| 17 || C  || center connection for relay 6\n|-  \n| 18 || NC  || normally closed contact for relay 6\n|-\n|}\n\n== Controlling the relays of Relay or BigRelay ==\nWith the 10 register you can turn everything on or off.  It is a bitmask register. (bw_tool uses hexadecimal numbers, so add the values for the diffrent relays together, 1,2,4,8, 10, 20 for relays 1-6.)  \n bw_tool -s 50000 -a 9c -W 10:0:b #Everything off\n bw_tool -s 50000 -a 9c -W 10:1:b #Relay 1 on\n bw_tool -s 50000 -a 9c -W 10:20:b #Relay 6 on\n\nYou can use register 20 till 25 to turn every single relay on or off. \n bw_tool -s 50000 -a 9c -W 20:0:b #Relay 1 off\n bw_tool -s 50000 -a 9c -W 25:1:b #Relay 6 on\n\nWhich method you use is up to you. If your program \"knows\" the state of all the relays, using register 0x10 may be easier. But if say you have one program controlling one relay and another program controlling another, using the 20-25 registers is probably easier.\n\n== LEDs ==\n\nThere is one power led. \n\nOn the regular relay board are two LEDs near each of the relays indicating the state of the relays. The BigRelay board doesn't have indication LEDs.\n\n\n== Related projects ==\n\n* [[Temperature_control]]\n\n== External resources ==\n\n=== Datasheets ===\n\n5A variant: [http://www.parallax.com/sites/default/files/downloads/27115-Single-Relay-Board-Datasheet.pdf Songle SRD-05VDC]\n\n10A variant: [http://www.omron.com/ecb/products/pdf/en-g5le.pdf Omron G5LE-1]\n\n== Additional software ==\n[[bw_tool]]\n\n== Changelog ==\n\n\n=== 1.0 ===\n* Initial public release"
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