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OpenParcelBox/hardware/reverse-engineering/kerong-kr-s79-20-jst.md
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KERONG KR-S79_20-JST

Status: Electrical characterization experimentally validated.

The information on this page comes from measurements performed on a new original Boks replacement lock. It may differ from other KR-S79 variants.


Identification

Item Value
Manufacturer KERONG
Model KR-S79
Variant KR-S79_20-JST
Revision 2023.10_KERONG
Manufacturing date 17-10-2023
Patent ZL.201821837049.2

Characteristics

Parameter Value
Supply voltage 8 to 24 V DC
Maximum current 100 mA
Auxiliary contact 3 A max
Connector JST
Harness length 20 cm

Manufacturer Pinout

Color Function
Red +V, 8 to 24 V
Orange GND
Yellow SIG
Black COM
Green NO
White NC

Boks Harness Mapping

Boks Side Lock Side Function
Blue Red +V
White Orange GND
Green Yellow SIG
Yellow Black COM
Black Green NO
Red White NC

Operation

Power Supply

The lock is continuously powered between:

Pin Function
Red +8 to +24 V
Orange GND

At rest, the lock remains closed.


Opening Command

Opening is triggered by a positive pulse on the SIG input.

Validated test:

Action Result
SIG connected to +V Opens
SIG connected to GND No effect

The lock therefore includes its own control electronics.


Feedback Contact

The lock includes a changeover contact.

Experimental Measurements

Locked

Measurement Result
COM to NO Continuity
COM to NC Open

Unlocked

Measurement Result
COM to NO Open
COM to NC Continuity

Note:

OpenParcelBox relies on the experimentally measured behavior rather than assumptions from markings alone.


State Detection

The contact changes state as soon as the latch leaves the locked position.

It is therefore not necessary to wait for the mechanism to complete its full travel before detecting unlocking.

This allows the firmware to detect the lock state almost immediately.


Wiring Diagram

+8 to 24 V
    |
    +-- Red (+)
        KR-S79
    +-- Orange (GND)

Yellow (SIG): positive pulse to +V opens the lock
Black  (COM): common feedback contact
Green  (NO):  closed when locked
White  (NC):  closed when unlocked

Validation

Function Status
Power supply Validated
Voltage Validated
SIG command Validated
Command polarity Validated
COM contact Validated
NO contact Validated
NC contact Validated
Opening detection Validated

Use in OpenParcelBox

This lock is compatible with the OpenParcelBox architecture.

The Seeed Studio XIAO BLE nRF52840 must:

  • Keep the lock powered.
  • Generate a positive pulse on SIG when opening is requested.
  • Monitor the COM/NC contact to confirm that the latch has left the locked position.

The COM/NC contact changes state as soon as the latch is released. It provides reliable feedback for confirming opening without waiting for a fixed delay.

The COM/NO contact is not currently used by OpenParcelBox.