Debounce HAT for Raspberry Pi
The Debounce Hat provides three pairs of opto-isolated, debounced digital inputs to a Raspberry Pi-compatible single board computer (SBC). All inputs accept 3 - 12V with arbitrary polarity and can alternatively be connected to open-collector outputs or mechanical switches leveraging the on-board isolated 5V supply.
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Prototypes of the Debounce HAT are currently undergoing testing and the product will soon enter the production stage. Please add your email address if you wish to stay updated on this product:
- 6 input channels (grouped as 3 pairs).
- Uncommitted inputs (100V channel-to-channel isolation).
- 2kV AC isolation between pairs (connector limited).
- 5kV AC (8kV HBM) opto-isolation to SBC logic.
- 4kV DC isolated 5V 200mA supply (DCDC converter limited).
- Two screw mounting points for earth connection.
- Spark gap overvoltage protection on all isolated connections.
- 2.5mm spring terminals for 0.2-1.0mm² wires (22-16AWG).
- 16 mm PCB height with connectors.
- JST XH / 0.1" screw terminal for 5V/2A input for 0.14-0.5mm² wires (26-20AWG).
- Raspberry Pi-compatible mounting hole pattern.
- Digital inputs with ESD protection.
- Mechanical switch / interlock inputs.
- Isolated sensor interface.
- Isolated DC voltage sensing.
See the HTML BOM for the values of the individual passive components. The 74LVT04 is in SOIC-14 form factor, the CAT24C32 EEPROM IC in SOIC-8. The LTV-824 optocouplers are in PDIP format.
The six channels of the board are mapped to the following GPIO pins:
- BCM 23 (WiringPi 4)
- BCM 26 (25)
- BCM 6 (22)
- BCM 5 (21)
- BCM 22 (3)
- BCM 17 (0)
With 5 VDC connected to the two-pole terminal, power is provided to the connected Raspberry Pi board using the GPIO header's 5V pins.
The inputs are driven with an external voltage in the range of 3 to 12V. With mechanical switches, a circuit has to be formed with the isolated DC header, or with an external power supply.
This board design is currently a work-in-progress and untested. We cannot accept any responsibility for design flaws, but we'll gladly accept feedback and suggestions for improvements.
The EEPROM configuration is provided in the
eeprom_setting.txt file, which can be processed with the
eepmake tool, and flashed to the EEPROM with
eepflash. Both tools can be found at https://github.com/raspberrypi/hats/tree/master/eepromutils. The jumper (three pin header) allows for the EEPROM to be set to write-protected/write-enabled mode (WP, WE, respectively).
[Warning] When not flashing the EEPROM, the EEPROM header should be set to Write-Protect (WP) mode by bridging the
[Write] pins on the three-pin header to prevent any accidental rewriting of the EEPROM's contents.
GitHub project page: https://github.com/MayaPosch/DebounceHat