rickyjar
Member level 2
User markosik20 found an interesting microcontroller and made this device.
The name Mini measuring Module came from the fact that the device can measure signals of bridge sensors (here from a tensometric sensor) in the range from several uV to 2.5V.
The heart of the module is a Silab'a C8051F353 controller. It is a modified version of the 8051 with a single-stroke instruction cycle and PLL on board, where full 50MHz can be reached.
On board there is a ADC Sigma Delta 16bit with PGA, 2x DAC outputs assembled, which enabled to create a circuit to measure very small signals.
The device presented has:
1. A RS232 or RS485 output with the implemented protocol MODBUS RTU.
2. An output in the form of a 4-20mA current loop created on an operational amplifier and voltage source.
3. An OC-type bit output to connect, e.g. a relay.
4. A bit input to be used as a key grounding, taring or starting collecting samples (max 100).
5. An input to insert a signal from the bridge, input for a external Vref connection and input for bridge power supply (5V).
+/-1uV resolution was obtained, which after converting gives 1000 measuring sections.
Unfortunately, the disadvantage of uC is its Flash memory capacity (8kB), however using the possibilities of the SDCC compiler and assembler insert, it was managed to support all the peripheries.
The board was made in home conditions.
As usually, some additional „modifications” were applied.
To control and configure the module, a proper software was created.
The scale module can be presented in its final version. It was managed to implement bootloader and several interesting functions.
The program has also evolved intensely:
Link to original thread - Mini Moduł wagowy - MODBUS oraz 4-20mA