This project has evolved from a classic MCU design using an STR912 ARM9 based micro controller to an mbed design. The primary reason for the migration to mbed was a ready to go local file system which allowed for easier uploading of new audio files to the robot. The upgrading of firmware was also easier as the both the audio files and the firmware can now both be upgraded via the USB interface.

The male mannequin was a German produced mannequin made by Loutoff and available to purchase from Ebay. The mannequin cost about £70 and was chosen as it looked like there was a degree of freedom in the shoulder which could be motorized with a little redesigning. The plan was to produce a motorized arm that could be raised and lowered at will. The hand at the end of the arm could be used to hold a variety of object including walking sticks, radar guns and water pistols.

Whilst not many of of you have a use for a motorized mannequin the technology inside the mannequin can be used for other projects. The technology includes the following key areas:

• motorized ARM This is based on a windscreen wiper motor, gearbox and cam assembly from an old Ford Fiesta and acquired from a local scrap yard for £30. It is controlled with a proportional speed control using a single PWM channel from the mbed. The motor speed can be altered throughout the raise and lower cycle to provide a smooth, natural motion of the arm. The motor drive power stage uses a fault protected MOSFET from ST Microelectronics, which is capable of surviving short circuit and a stalled arm, and over voltage stresses from the motor. The circuitry can also monitor the current flowing in the motor during the raise and lower cycles by providing an analogue current feedback signal to the mbed. This means the mbed can detect a stall condition (due to obstruction) and can safely turn off the motor drive to prevent damage to the motor and the mannequin

• voice/wav player The mbed is equipped with a DAC-OUT analogue output signal and this signal is used to drive an audio power amplifier TDA2050 from ST Microelectronics. The power amplifier is capable of delivering enough audio power for it to be too loud to stand next to. This is ideal for outside use. The audio signals are .wav files which are downloaded from the USB interface on to the local file system on the mbed module. The .wav files are copied from the local file system into M25P64 serial flash memory, where they can be replayed at full speed when required by the mbed.

• local file system for uploading new audio The local file system is too slow for replaying .wav files at full speed so the mbed will copy across any .wav files into an external M25P64 serial flash memory. A naming convention for the files is used to identify which audio tracks you want synchronized with the arm movement and which ones you want to be played periodically but without any arm movement. For example a gun shot sound can be played in sync with the arm movement whilst a burping noise can be played independently of any arm movement.

• An external switch input for Passive Infra Red Detection A PIR movement detector can be connected to the robot so the voice and arm movements can be synchronized with the detection of an intruder for example, or the motion of a passing car.

• In external I2C Interface for connection to a shock sensor Provision has been made in this circuit to allow for an external I2C shock sensor such as the devices from ST Microelectronics motion sensors. The I2C devices provide an x,y and z signal for acceleration and hence make an ideal shock sensor. The external I2C bus can be used for other I2C peripherals as well, not just shock sensors.