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Shooting Chrony PC Serial Interface

Shooting Chrony sells a PC interface cable for use with the Chrony for around $23. If the parts to build the interface are not readily available or constructing a board with surface mount parts is an issue then buying the Chrony interface cable is a good choice.

The Chrony uses a 3.5mm (1/8") stereo jack as the serial port connector. This connector is also used for the remote button interface. The following diagram shows the signal locations on the plug. The signals are 5V digital I/O and need to be translated to RS-232 levels before being connected to a PC. The signals are named from the Chrony's perspective; e.g. after level shifting the TX signal is connected to the PC's RX line.

Chrony Serial Plug Diagram

The following schematic has been used to connect to a Chrony using a serial terminal emulation application, it has not been tested with the Chrony Ballistics II software or any other ballistics software. Q1 and Q2 are N-Channel MOSFETs with an ESD protected gate. The gate of a regular 2N7002 is susceptible to being destroyed by electrostatic discharge and proved to be a problem on early prototypes. Having the gate of a FET at the tip of a stereo jack is always going to be a problem.

Chrony Serial Schematic Diagram

Parts List
Designator Description Manufacturer Mfg PN Digi-Key PN
J1 CONN DB9 FEMALE SLD CUP NICKEL Norcomp Inc. 171-009-203L001 209FE-ND
J2 CONN AUDIO JACK 3.5MM STEREO SMD CUI Inc. SJ-3523-SMT CP-3523SJCT-ND
Q1, Q2 MOSFET N-CHAN 154MA 30V SOT-416 ON Semi. NTA7002NT1G NTA7002NT1GOSCT-ND
R1 RES 2.2K OHM 1/8W 5% 0805 SMD Rohm MCR10EZPJ222 RHM2.2KARCT-ND

The image below shows the location of the parts on the board. The board is about 0.960 x 0.520 inches and fits between the pins of the DB-9 connector. The board was fabricated using Techniks Press-n-Peel Blue on 1/16" thick single-sided stock. The PDF file used to produce the board is available here.

Chrony Serial Board Assembly

The assembled board is shown below.

Chrony Serial Board Assembly

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Copyright © 2008, Jesse Marroquin. All rights reserved.
Last modified: July 15, 2008