DAS201 MiniDAS

The DAS201 MiniDAS is a single-board DAQ with the following block diagram (MAY16).

  1. The 5 input channels are designed for precision interchangeable thermistors (0-105 degC) but can instead be voltage inputs of 0 V to 4 V fs.

  2. The two digital inputs can detect switch closures or more generally be bit inputs.

  3. The serial synchronous two-bit interface extends the I/O of the DAQ.

  4. The user output is 6 7-segment LEDs.

  5. The user input is a 4-button switch-mouse: MENU (or ESC), ENTER, UP, and DOWN for traversing menu trees and numeric entry.

  1. A jumperable watchdog timer circuit drives the /NMI input of the 6502 mP.

  2. A reset IC initiatess the mP reset computing thread at power-on.

  3. Input power is 6.3 V rms from which is generated 5 V and -5 V.

  4. Two optionally optoisolated output bits - for datalogging or control.

  5. Data acquisition is through an 8 channel MUX followed by a VFC that drives the mC counter input.

  6. The VFC IC (an LM331) and op-amp output a buffered reference voltage, VR = 4.0 V for ratiometric input dividers.

  7. Two of the 8 channels have precision 1/4 and 3/4 dividers with 0.1 % resistors from VR for two-point calibration.

  8. All connections are along one terminal strip along the bottom side of the circuit-board.


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