I2C – Model Rail Electronics

DS209 – I2C hub extender

Model Rail Electronics — Sun, 01 Mar 2026 22:10:38 +0000

Version 1.0

The DS209 – I2C hub extender can be used to add extra I2C connections to the DS208 I2C hub.

DS208 – I2C hub

Model Rail Electronics — Sun, 01 Mar 2026 22:02:21 +0000

IN TESTPHASE

Version 1.0

The DS208 – I2C hub can be used to connect multiple I2C modules to one bus. The module has it’s own 5V voltage regulator circuit and level shifters on the module allow the module to be connected to either 3.3V or 5V I2C bus.

DS207 – I2C relay module

Model Rail Electronics — Sun, 01 Mar 2026 21:53:01 +0000

Version 1.0

The DS207 – I2C relay module is an 8 channel relay module. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used.

The module has two common pins labeled C1 and C2 and each relay has it’s own output pin (Normally Open connected to C2, when activated connected to C1). To minimize power consumption the module is equipped with low current LEDs but if no indication is needed, these LEDs can be turned off by removing jumper J2.

The DS207 – I2C relay module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P7
Channel 6 = P6
Channel 7 = P5
Channel 8 = P4

Built time for an experienced tinkerer: 30 ~ 40 minutes.

DS206 – I2C switch module

Model Rail Electronics — Sun, 01 Mar 2026 21:48:22 +0000

Version 1.2

The DS206 – I2C switch module is an 8 channel switch module which uses 2 IC’s of type ULN2803 to control electrified turn outs. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used.

The module has two pins labeled C- and C+ for the coil voltage (12-18V DC) for your turn outs. There are two additonal C+ connections for the common wire and ports 1 to 8 can be used to control each coil of a turn out. Therefore a total of 4 turn outs can be controlled with one module.

The DS206 – I2C switch module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P4
Channel 6 = P5
Channel 7 = P6
Channel 8 = P7

Built time for an experienced tinkerer: 20 ~ 30 minutes.

DS205 – I2C reverse loop module

Model Rail Electronics — Sun, 01 Mar 2026 21:37:11 +0000

IN TESTPHASE

Version 1.0

The DS205 – I2C reverse loop module has connections for track signal, section A, section M (middle) and section B. Sections A and B have current detection and the module acts as feedback decoder for these two sections. This module has 3 relays, for each section one relay. The connected Arduino needs to take care of controlling these relays depending on the feedback information received. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used. Starting from software version 0.91 the reverse loop functioning is included in the sketch so the module will only act as feedback decoder if necessary.

The DS205 – I2C reverse loop module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel A = P0
Channel B = P1
Relay A = P5
Relay M = P6
Relay B = P7

Built time for an experienced tinkerer: 30 ~ 40 minutes.

DS204 – I2C sensor module

Model Rail Electronics — Sun, 01 Mar 2026 16:44:41 +0000

Version 1.2

The DS204 – I2C sensor module is an 8 channel sensor module. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to LocoNet, the DS104 – Lnet I2C interface can be used.

The module has 8 triple pins providing 5V, GND and an IN pin for connecting infra red sensor modules (active high) or hall sensors (active low) like the 44E hall sensor.

The module has 2 jumpers to determine if the input pins should be high by default (needed for 44E hall sensor) or low in two sets of pins: J11 controls ports 1 to 4 and J12 controls ports 5 to 8.

The DS204 – I2C sensor module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P4
Channel 6 = P5
Channel 7 = P6
Channel 8 = P7

Built time for an experienced tinkerer: 15 ~ 20 minutes.

DS202 – I2C mass detection module

Model Rail Electronics — Sun, 01 Mar 2026 16:18:36 +0000

Version 1.2

The DS202 – I2C mass detection module is an 8 channel mass detection module. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used.

The module has one common pin labeled C and each detection circuit has it’s own detection pin. It detects a connection between each detection pin and the common pin so it can therefore be used with reed contacts or switches.

The DS202 – I2C mass detection module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P4
Channel 6 = P5
Channel 7 = P6
Channel 8 = P7

Built time for an experienced tinkerer: 20 ~ 30 minutes.

DS203 – I2C relay module

Model Rail Electronics — Tue, 25 Feb 2025 16:20:21 +0000

Version 3.4

The DS203 – I2C relay module is an 8 channel relay module. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used.

The module has one common pin labeled C and each relay has it’s own output pin (Normally Open). To minimize power consumption the module is equipped with low current LEDs but if no indication is needed, these LEDs can be turned off by removing jumper J2.

The DS203 – I2C relay module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P7
Channel 6 = P6
Channel 7 = P5
Channel 8 = P4

Built time for an experienced tinkerer: 30 ~ 40 minutes.

DS201 – I2C current detection module

Model Rail Electronics — Tue, 25 Feb 2025 11:55:40 +0000

Version 3.4

The DS201 – I2C current detection module is an 8 channel current detection module. It has the same pinout as the PCA9685 PWM module and can therefore be connected in the same way. For connecting this module to Loconet, the DS104 – Lnet I2C interface can be used.

The module has one common pin labeled C and each detection circuit has it’s own detection pin.

The DS201 – I2C current detection module is sold as do it yourself project containing PCB and all components.

Programming info:
I2C address configurable using jumpers on J1 (A2-A1-A0):
0-0-0: 0x20
0-0-1: 0x21
0-1-0: 0x22
0-1-1: 0x23
1-0-0: 0x24
1-0-1: 0x25
1-1-0: 0x26
1-1-1: 0x27

Pinlayout on I2C IC:
Channel 1 = P0
Channel 2 = P1
Channel 3 = P2
Channel 4 = P3
Channel 5 = P4
Channel 6 = P5
Channel 7 = P6
Channel 8 = P7

Built time for an experienced tinkerer: 30 ~ 40 minutes.

PCA9685 16 Channel 12-Bit PWM Servo Shield Driver I2C Interface

Model Rail Electronics — Tue, 05 Sep 2023 20:49:23 +0000

Dimensions (no headers or terminal block) 2.5″ x 1″ x 0.1″ (62.5mm x 25.4mm x 3mm)
Weight (no headers or terminal block): 5.5grams
Weight (with 3×4 headers & terminal block): 9grams
This board/chip uses I2C 6-bit address between 0x40-0x7F, selectable with solder pads
Terminal block for power input (or you can use the 0.1″ breakouts on the side)
Reverse polarity protection on the terminal block input
Green power-good LED
3 pin connectors in groups of 4 so you can plug in 16 servos at once (Servo plugs are slightly wider than 0.1″ so you can only stack 4 next to each other on 0.1″ header
“Chain-able” design
A spot to place a big capacitor on the V+ line (in case you need it)
220 ohm series resistors on all the output lines to protect them, and to make driving LEDs trivial
Solder jumpers for the 6 address select pins
i2c-controlled PWM driver with a built in clock. Unlike the TLC5940 family, you do not need to continuously send it signal tying up your microcontroller, its completely free running!
It is 5V compliant, which means you can control it from a 3.3V microcontroller and still safely drive up to 6V outputs (this is good for when you want to control white or blue LEDs with 3.4+ forward voltages)
6 address select pins so you can wire up to 62 of these on a single i2c bus, a total of 992 outputs – that’s a lot of servos or LEDs
Adjustable frequency PWM up to about 1.6 KHz
12-bit resolution for each output – for servos, that means about 4us resolution at 60Hz update rate
Configurable push-pull or open-drain output
Output enable pin to quickly disable all the outputs
(1)Drive board connected to Arduino:
The PWM driver board uses the I2C method, so only four lines can be connected to the Arduino device:
“Classic” Arduino pin mode:
+ 5v -> VCC
GND -> GND
Analog 4 -> SDA
Analog 5 -> SCL
Old Mega pin way:
+ 5v -> VCC
GND -> GND
Digital 20 -> SDA
Digital 21 -> SCL
R3 and later Arduino pin method (Uno, Mega & Leonardo):
(These boards have dedicated SDA and SCL pins)
+ 5v -> VCC
GND -> GND
SDA -> SDA
SCL -> SCL
VCC pin is only for the chip power supply, if you want to connect the servo or LED lights, use the V + pin power supply, V + pin supports 3.3 ~ 6V power supply (chip safe voltage 5V). It is recommended to connect the external power supply via the power supply terminal.
(2) power supply part:
Most of the servo design voltage is 5 ~ 6V, especially in a number of steering gear at the same time running, with the need for high-power power supply. If you are directly using the Arduino 5V pin to power the servo directly, there are some unpredictable problems, so we recommend that you have a suitable external power supply for the drive board.
(3) Connect the servo:
Most servos are connected using standard 3-wire female plugs, as long as the corresponding pin into the driver board on it. (Ground wire is generally black or brown, the signal line is generally yellow or white)
(4) for the driver board assigned address:
Each drive board of the cascade needs to have a unique access address. The initial I2C address of each driver board is 0×40, you can modify the upper right corner of the jumper I2C address. Connect two solder pads to indicate a binary number “1”.