Freescale is demonstrating a non-contact proximity sensor reference platform. This platform is based on Freescale's MC33794 proximity sensor, which generates a low-level electric field and uses feedback to detect the presence of objects. Freescale's proximity sensors provide solutions for automotive electronics and industrial control manufacturers who are designing systems that detect objects without direct contact.
Proximity sensing offers reliability advantages over traditional methods that require physical contacts, which can deteriorate due to wear and become less dependable over time. Freescale's e-field technology has been applied in vehicle occupant sensing systems, touch panels and liquid level sensing applications. Automotive equipment manufacturers can use the e-field technology as an alternative to mechanical systems for liquid-level detection applications. The technology is usefull for designing intelligent airbag systems that detect passengers. In addition, e-field technology can enhance human machine interface (HMI) dashboard applications designed to make the driving experience easier and more comfortable.
Proximity sensor reference platform features
- Human touch detection through the touch pad and slider board
- Water level detection through the water pump and water slider board
- Based on MC33794 proximity sensor with 9 + 1 electrodes 8-bit microcontroller (MC68HC908QB8)
- Multiple switch detection interface (MC33993) drives LEDs
- H-bridge motor driver (MC33886) serves as a water pump
- Input supply voltage +12V DC / 2A
- 7-segment numeric LED display and LED bar graph
- Connection with a PC via RS232 (FreeMASTER GUI)
E-field sensors
Designed for applications that require non-contact sensing of objects, the MC33794 sensor contains circuitry to generate a low-level electric field and measure the field loading caused by objects moved into the field. The MC33794 generates a low-frequency sine wave, and the frequency is adjustable by using an external resistor and performs optimally at 125 KHz. The MC33794 supports up to 66 touch points and up to 11 electrodes and includes watchdog and power-on-reset timers.
A cost-effective alternative to the MC33794, the MC34940 addresses the appliance and industrial markets. The MC34940 is suitable for implementing proximity detection and three-dimensional e-field sensing. It is able to trigger functions such as turning switches on or off, disabling features or setting off alarms to indicate dangerous situations for devices such as coffee pots, hair dryers and lawnmowers. The MC34940 supports up to 28 touch pad sensors and up to seven simple electrodes, which when used independently, can provide information to perform multiple functions simultaneously.
