BusIO address, Trig threshold, NFB control (in beta stage).Ī sensor may be interrogated for raw sensor value while in standby. The sensor stores configuration data in the microcontroller's flash memory. Flashing activates/deactivates via a command received over BusIO. 1-48 of 167 results for 'piezoelectric disk' Results Price and other details may vary based on product size and colour. As the piezo sensor is practically limited to a length of sampling time (a few seconds to a minute) the alarm condition self cancels after sending a set number of raw sensor values. If the peizo voltage changes by a set threshold, an alarm condition. The last three historical raw sensor values before the trigger occured are sent out on BusIO, followed by ongoing real time raw sensor values during the alarm event. During a trigger this fine tuning is temporarily disabled. As mentioned earlier the microcontroller continually monitors the peizo voltage and fine tunes it with narrow maintanence pulses when needed. No BusIO data is sent out but it listens for configuration commands. Standby. The sensor raw value is sampled several times per second and the last few values are kept in a buffer. During aquisition of 50% point the sensor sends out raw signal level data messages on BusIO to show the stabilisation is in progress. This is done with another pin on the microcontroller (3-state narrow pulses via 220 K resistor) to trim the peizo voltage up or down accordingly to stabilse it at the 50% point. To ensure input always operates within ADC range the microcontroller stabilises the voltage on the piezo disc at 50% supply voltage. The peizo is effectively a capacitor referenced to ground and can retain its charge for a considerable time. Stabilisation. The peizo is directly connected to a AtoD input. A completely standard terminal program may be used to create a BusIO environment for monitor BusIO communications and command any sensor. It has some similarities with I2C in its operation but it allows the connection of standard RS232 (TTL levels) interfaces to simplify project development and debugging. The bidirectional serial interface is mentioned in my other project "BusIO". The trigger threshold is programmable through the same BusIO serial interface. If the voltage exceeds a set threshold the microcontroller sends alarm messages through a bi-directional serial interface (BusIO), a 16 bit length message. The microcontroller senses the piezo voltage with its ADC. In contrast to a conventional resistive strain sensor which outputs a stable signal, the piezo generates a transient signal. Otherwise a mechanical strain sensor would otherwise be done with a Strain Guage which produces a tiny resistance change according to mechanical deformation which requires careful amplification at microvolt levels.Ī piezo sensor instead has a much lower part count. What's novel is the extreme simplicity of design thanks to the high sensitivity of the piezo element used as the sensing element. This sensor will easily detect the distortion of sheet of steel or glass it is attached to.
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