Technical specifications of the HBD


To be filled when a functioning device is built. At the moment, we are still in an Alpha phase, but making some progress. See below for already available data.

Overall system schematic

Here a schematic overview of the HBD is available. Some things are noted in German. Achszähler would be "axle counter" , and Taster is "push button"; the rest should be clear.


Schematic

Version 0.9d
This revision corrects an error where the relais activating the radio had been accidentally inserted in the wrong place. It is now between the 10k potentiometer and the radio's microphone input.
The corrected version is available here.
Please substitute the 74HCT4050 and the two transistors interfacing the controller and the Flash with a MAX3392E, while waiting on the next revision.

Version 0.9c
There is a new schematic available: version 0.9c. You can find it here (730 kiB).

The jumpers/bridges B1..3 allow you to select either the speaker output or the radio interface. Additionally, it is possible to isolate the relay and connect external circuitry via the terminal points (TP), in case you want to use it otherwise (e.g., in the Italian version of the HBD we make use of it). This arrangement allows a single PCB design to cover different versions.
Again, power circuitry is not shown, but I plan to do so in the final version.

Version 0.9a
Obsolete: Version 0.9a of the schematic is available, see this link.
Missing is:

  • current supply
  • level shifters
  • matrix keyboard
  • radio monitor input (pin 19)

Source files

Preliminary source code

Version 0.9[download]