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projects:crazyflie:hardware:explained [2012-12-03 22:13] tobias [Expansion header] |
projects:crazyflie:hardware:explained [2014-11-17 06:19] chad [LiPo] Small spelling correction |
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- | ====== Crazyflie KIT electronics explained ====== | ||
- | This section is here to explain all high level electronics used in the Crazyflie. | ||
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- | ===== Electronics overview ===== | ||
- | {{: | ||
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- | ===== Battery ===== | ||
- | {{: | ||
- | The battery we use is of the type LiPo (Lithium-Polymer). They are currently the most popular battery type for R/C use. The LiPo is hoverer not the safest chemistry and should be handled with care. Failing to do so could make it catch on fire. It is also sensitive to under/over charge, to high discharge/ | ||
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- | ==== PCM ==== | ||
- | To handle some of the LiPo shortcomings we use a PCM (Protection Circuit Module) that will prevent the user from under/over charging or shorting it. The PCM is located under the orange tape on the top side of the battery where the wires come out. | ||
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- | The PCM has the following spec: | ||
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- | || Item || Specification || | ||
- | || Overcharge detection voltage | ||
- | || Overcharge release voltage | ||
- | ||Overcharge | ||
- | || Over discharge detection voltage | ||
- | || Over discharge release voltage | ||
- | || Over discharge detection delay time || 115~173 ms || | ||
- | || Over discharge current | ||
- | || Over discharge current delay time || 7.2~11ms | ||
- | || Short detection delay time || 220~380us | ||
- | || Short release condition | ||
- | || Current consumption | ||
- | || Suggested max continuous charge/ | ||
- | || Suggested operation temp || -20 - +60 deg C|| | ||
- | || Internal resistance | ||
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- | ==== LiPo ==== | ||
- | The LiPo used is the **671723HS25C** from [[http:// | ||
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- | Specification: | ||
- | || Model || Voltage (V) || Capacity (mAH) || Thickness (±0.2) || Width (±0.5) || Height (±0.5) || Weight (g) || Charge Rate || Continues Discharge Rate || Burst (≤5S)|| | ||
- | || 671723HS25C || 3.7 || 170 || 6.9 ||17 || 23 || 3.9 || 1C-5C || 25C (≥ 80%) || 50C || | ||
- | {{: | ||
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- | === Connector === | ||
- | The connector we use is on the battery side is the [[http:// | ||
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- | ==== Replacing ==== | ||
- | It is possible to replace the battery with another LiPo to get longer flight times or make it lighter. Best would be to fit the new LiPo with the same connector, it is common and can be bought at most distributors, | ||
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- | We have tested several sizes of LiPo batteries, 100mAh to 400mAh, and found out that 150mAh to 250mAh is the sweet spot giving the best flight performance. | ||
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- | ===== Power management ===== | ||
- | {{: | ||
- | The power management is mainly handled by the [[http:// | ||
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- | ===== MCU ===== | ||
- | The MCU (Micro Controller Unit) we use, the brain of the Crazyflie, is the ST Microelectronics STM32F103CB. We actually choose this MCU in 2009 and now it is very commonly used by hobbyists and other UAV platforms. The STM32F103CB MCU we run at full speed, 70Mhz, and it has 128Kb flash and 20Kb RAM. As of December 2012 our current firmware takes 46kb flash and 16kb RAM. The RAM can definitely be more optimised so there are plenty of room to implement more algorithms and fun stuff. We use about 40% of its processing power (with a stabilization update loop at 500Hz) and a big chunk of this is because we use a " | ||
- | ===== Sensors ===== | ||
- | As for sensors we run a " | ||
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- | With a 6-axis system it is not possible to remove the yaw drift and for an autonomous system this could important. Therefore it is possible to manually solder-mount an magnetometer HMC5883L/ | ||
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- | It is also possible to manually solder-mount a MS5611 pressure sensor afterwards if that is of interest. This could make it possible add an altitude-hold functionality. No SW support now though. | ||
- | ===== Expansion header ===== | ||
- | {{: | ||
- | The expansion header is located on the left side of the Crazyflie. It is a 10x2 pin 1.27mm (0.05" | ||
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- | The header is divided into two parts. The JTAG part, pin 1 to 10, and the buss/power part, pin 11 to 20. The UART RX/TX is located on the JTAG part because on many FTDI based JTAGs it is possible to use one channel for serial communication which can be very handy when debugging. | ||
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- | Header pin description | ||
- | || Pin nr || Name || Description || | ||
- | || 1 || VCC || Digital supply voltage || | ||
- | || 2 || TMS || Test Mode Select || | ||
- | || 3 || EXT_I2C_SCL/ | ||
- | || 4 || TCK || Test Clock || | ||
- | || 5 || EXT_I2C_SDA/ | ||
- | || 6 || TDO || Test Data Out || | ||
- | || 7 || N/A || Could be used for keying || | ||
- | || 8 || TDI || Test Data In || | ||
- | || 9 || DGND || Digital ground || | ||
- | || 10 || SNRST || System reset || | ||
- | || 11 || EXT_SPI_CS/ | ||
- | || 12 || EXT_SPI_MOSI/ | ||
- | || 13 || EXT_SPI_SCK/ | ||
- | || 14 || EXT_SPI_MISO/ | ||
- | || 15 || VCC || Digital supply voltage || | ||
- | || 16 || VCOM || Battery/USB voltage || | ||
- | || 17 || DGND || Digital ground || | ||
- | || 18 || DGND || Digital ground || | ||
- | || 19 || AGND || Analogue ground|| | ||
- | || 20 || VCCA || Analogue supply || | ||
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- | ===== 2.4GHz radio ===== | ||
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- | ===== Motor drivers ===== | ||
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- | ===== Motors ===== | ||