Commit 8cd88f9d authored by Jonathan Lock's avatar Jonathan Lock

Initial version

# rabidmantis
Open-source-hardware projects with fairly extensive documentation.
Feel free to contact rabidmantis >at< lerneaenhydra >dot< net!
# Braking resistor
Braking Resistor is, as it's name suggests, a general-purpose braking resistor primarily intended for handling regenerative power from low to mid-power servo and stepper-motor drives.
An external high-power shunt resistor is switched on, draining power from the bus when the bus voltage exceeds some limit V_{bus,high}, and kept on for at least t_{min} and until the bus voltage falls below V_{bus,low}.
Braking Resistor can be used with bus voltages ranging from 12 V to 75 V, and can sustain an average load of 8 A, or 35 A at a 5% duty cycle with 1 ms pulses, with the default pass transistor. Other transistor choices allow operation at up to 300 V and significantly higher currents.
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# Cheapamp
The Cheapamp amplifier is a compact general-purpose --- though audio-oriented --- class-D power amplifier with analog volume controls and a pin-header for full digital control. It is based on the MAX9736A/B monolithic amplifier.
The board design is heavily centered around the filter-less recommended design shown in the datasheet, and is configurable for either mono (bridged) or stereo applications.
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# Compact Crossover
Compact Crossover is a general-purpose active constant-voltage audio crossover filter (i.e. a filter with a completely flat phase response. This is the only crossover filter type that passes a square wave input signal completely unaltered, and as such is the only filter type that is completely transparent in the ideal case.).
By resistor choice the cutoff frequency is effectively arbitrary and maintains a stop-band attenuation of 12dB/octave (40dB/decade). Only through-hole components are used, making it easy to assemble. It is capable of running either from a single supply voltage (10-20V) or a dual supply (\pm 5V to \pm10V). An optional mode, with fewer mounted components, allows it to function as an ultrasonic/infrasonic bandpass filter, passing signals in the audio range (1.5Hz to 58kHz).
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# Flexible Servo Controller
Flexible Servo Controller is, as its name suggests, a multi-use servo controller for brushed DC motors with incremental encoder feedback capable of driving motor currents of up to 25 A continuous (10 A continuous without active cooling) at supply voltages of up to 42 V (limited by an absolute maximum of 50 V).
The input position setpoint uses an encoder-like quadrature (A/B) interface and supports speeds up to 1 MHz. A configurable charge pump or active-low input activates the controller, bringing the output out of a configurable off state (brake or coast). Logic outputs are a controller active output, a fault output, and an encoder index output. A serial UART interface (RX/TX) allows for configuring and reading the system state with a command line interface which offers easy access to read and modify the system configuration, tune the controller parameters, read any logged system faults, and save settings to nonvolatile memory.
A programmer capable of programming devices over the PDI interface (such as an AVRISP MKII) and a serial terminal, such as a USB to UART converter (3.3/5 V compatible) are required to program and configure Flexible Servo Controller.
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# Isolated USB-UART
Isolated USB-UART is a galvanically isolated USB to UART converter. It is based on the FT232R and ADuM1201 IC's and offers speeds up to 3Mbaud (1Mbaud with the default components) with support for up to three data transfer pairs, RX/TX, RTS/CTS, and DSR/DTR, controllable by component mounting choices. Galvanic isolation of up to 1131V is achievable as per the IEC 60950-1 standard, making mains isolation easily achievable. A 2.7V to 5.5V output voltage range allows for communication with most devices. An optional mode supplies the load with 5V from the USB bus, though without any isolation.
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# Temperature Controller
Temperature Controller is a general-purpose temperature controller that can be used for any single-ended load such as a resistive heater, cooling fan, refrigerator/freezer, either directly or through some intermediary (such as a relay).
The control law can be varied from a linear ramp in power between two levels to a purely hysteric output, with an additional minimum duty cycle and minimum switch period. Complementary OK and ERROR outputs indicate a temperature-out-of-range and/or temperature-sensor error condition. A rotary encoder and three-digit seven-segment display is used to configure parameters and display the current temperature.
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# Waveplayer
Waveplayer is a general-purpose, standalone, stereo audio playback board. Wave files are read from a removable microSD or microSDHC card (up to 32GiB) with a FAT12/FAT16/FAT32 file system. Files with any combination of mono or stereo, 8-bit or 16-bit, and 8/11.025/16/22.05/32/44.1/48kHz sample rates are supported.
Waveplayer's analog output has an SNR level exceeding 90dB at full output amplitude and an estimated THD typically under 0.005% (3.9Vpp, 1kHz). A low-power mode allows for battery powered applications, with an idle-state current draw of typically 1.7 mA.
Six user-configurable inputs are available for triggering events (play, pause, next track, etc) on a rising or falling flank. One of these inputs can be used as an analog input for controlling the playback amplitude from -100dB to 0dB with a linear change in voltage.
A header row allows for directly connecting Waveplayer to a Cheapamp board (another rabidmantis OSHW project), for a complete audio amplifier system.
An integrated serial interface can be used for more complex control and allows for navigating the file-system, controlling the playback state, and changing system settings.
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