Advanced serial interface module (RS232 IO)

From CaveLab
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This module was part of the rack box project — which was terminated when I moved out of my first apartment.
ASIM installed in the Rack box.

Serial (RS-232) interface module; providing 6 analog and 2 digital inputs, and 9 digital outputs. Uses an AVR ATmega8 microcontroller.

Details

ASIM provides 6 analog and 2 digital inputs, and 9 digital outputs for the computer serial port. The outputs give GND when activated, max load pr. channel: 100mA. The digital inputs are triggered when they are connected to GND, the analog inputs need to be queried for the value. The A/D converter is 10-bit, so 0-5 volt is reported back as 0-999. For sensors outside the Rack box, a 1uF capacitor is connected between GND and the signal input, this removed noise and allows for a stable input signal.

This module measures the voltage of the 5, 13.8 and 24 volt supply and the Rack box temperature (LM35). The two auxiliary analog inputs can be connected to any 0-5V voltage sensor, currently connected to two external LM35 temperature sensors.

By sending commands to the module one can change the status of the outputs, the module will confirm when the action is carried out. It's possible to ask for the current status of any in- or output, this is done by not sending a set value. All commands from the module is sent with a checksum.

I/O

Inputs

  • PC0 5V voltage meter
  • PC1 13.8V voltage meter
  • PC2 24V voltage meter
  • PC3 Temperature rack box
  • PC4 Input 5 (Analog)
  • PC5 Input 6 (Analog)
  • PD5 Input 7
  • PD6 Input 8

Calculations

Voltage
Temperature

Outputs

  • PB0 Output 1
  • PB1 Output 2
  • PB2 Output 3
  • PB3 Output 4
  • PB4 Output 5
  • PB5 Output 6
  • PB6 Output 7
  • PB7 Output 8
  • PD2 Output 9
  • PD3 Lifesignal (to Module stability monitoring unit 2)
  • PD4 Link activity

D-sub 25-pin

  1. 13.8V
  2. 0V
  3. Input 5V (Analog)
  4. Input 24V (Analog)
  5. 5V to analog sensor
  6. 0V to analog sensor
  7. Input 5 (Analog)
  8. Input 6 (Analog)
  9. Input 7
  10. Input 8
  11. Output 1
  12. Output 2
  13. Output 3
  14. Output 4
  15. Output 5
  16. Output 6
  17. Output 7
  18. Output 8
  19. Output 9
  20. Lifesignal

Communication

Interfacing is done with RS-232, using MAX232 or MAX202.

Serial settings

Baud
9600
Data bits
8
Parity
None
Stop bits
1
Start command
0
Module ID
005

Source code

Git-alt-brands.svg
Bascom-AVR source is available in a git repository:
https://github.com/thomasjsn/AVR-Advanced-serial-interface-module

Gallery

  • Box drilled

  • Required wires

  • Box inside

  • Box front

  • Working on PCB

  • Working on PCB

  • Working on PCB

  • Working on PCB

  • Working on PCB

  • Working on PCB

  • Assembly

  • Assembly

  • Assembly

  • Module complete

  • Connecting cables

  • Installing in the Rack box

  • ASIM installed in the Rack box

  • Connection block

  • External temperature sensor

  • External temperature sensor in lower part of rack.

  • External temperature sensor PCB

  • External temperature sensor by desk

  • External temperature sensor capacitor

  • Dsc-0532-49rkw4.jpeg
  • Dsc-0533-gr916g.jpeg
  • Dsc-0534-41mx34.jpeg
  • Dsc-0535-gvr854.jpeg
  • Dsc-0536-4wr38g.jpeg
  • Dsc-0537-gkzr1g.jpeg
  • Dsc-0538-qe0704.jpeg
  • Dsc-0539-4587v4.jpeg
  • Dsc-0540-g2zm1g.jpeg
  • Dsc-0541-4lw1zq.jpeg
  • Dsc-0542-4nexz4.jpeg
  • Dsc-0543-4d96oq.jpeg
  • Dsc-0544-gpxen4.jpeg

Schematic drawing

Asim circuit.png

Parts list

Qty. Part
1 × AVR ATmega8-16PU, DIL-28, 16 MHz, 23 I/Os
5 × Capacitor, aluminium electrolytic, 1 µF, 50V
1 × Capacitor, aluminium electrolytic, 10 µF, 25V
2 × Capacitor, aluminium electrolytic, 47 µF, 25V
2 × Capacitor, ceramic, 1 nF, 100V
2 × Capacitor, metallized polyester foil, 10 nF, (0.01 µF)
1 × D-sub soldering cups, 25 pin male
1 × D-sub soldering cups, 9 pin female
1 × DIL socket, 16-pin, 7.62mm
1 × DIL socket, 28-pin, 7.62mm
1 × Enclosure, plastic (1591 FL), 150x80x50mm, flange
1 × Fuse 5x20 mm, 1 A, fast-acting
1 × Fuse holder, panel, 5x20mm, PTF30
1 × Heatsink, 27.3K/W, 19mm, attachable, TO220
1 × LED 5mm clear, Green, 2.1V, 20mA, 385mcd, 6°
1 × LED 5mm clear, Yellow, 2.0V, 20mA, 250mcd, 6°
2 × LED holder 5mm, Black plastic
64 cm2 PCB, stripboard, 100x160mm, 160cm2
4 × Resistor, carbon film, 0.25W, 330 Ω, 5%
11 × Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
2 × Resistor, carbon film, 0.25W, 10 kΩ, 5%
3 × Resistor, carbon film, 0.25W, 100 kΩ, 5%
3 × Resistor, metal film, 0.6W, 20 kΩ, 1%
1 × RS232 interface, MAX232CPE, dual
1 × Spacer, round unthreaded, 3mm, Ø6mm, Delrin
33 × Straight pin header, female, Single row, 2.54mm
33 × Straight pin header, male, Single row, 2.54mm
1 × Temperature sensor LM35DZ, 0 to +100 °C, +-0,6 °C
10 × Transistor, NPN, 100 mA, 45V, 0.5W, BC547B
1 × Voltage regulator +5V, 2 A, L78S05CV

External temperature sensor

Qty. Part
1 × Capacitor, aluminium electrolytic, 1 µF, 50V
1 × Capacitor, aluminium electrolytic, 10 µF, 25V
1 × Capacitor, metallized polyester foil, 10 nF, (0.01 µF)
2 m Control cable, 4-cores, 0.25mm2, 250 V, Ø 4.6mm
1 × Enclosure, plastic (1551), 50x50x20mm
1 × Resistor, carbon film, 0.25W, 75 Ω, 5%
1 × Temperature sensor LM35DZ, 0 to +100 °C, +-0,6 °C
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