Today’s layouts may have multiple lighting or automated elements. Your layout may include signals or crossing flashers, or even working traffic lights. You may have street lights or prelit buildings that you want to be able to set custom brightness. You may have servo powered turnouts or other moving features such as crossing gates. Perhaps you want to have some special effects, such as simulating incandescent or fluorescent lighting, or perhaps a fire or welding simulation.
When you want to control a servo, and/or do more with layout lighting than just turning LEDs on or off — when you want to control brightness and run simulations — you need PWM ports. PWM (Pulse Width Modulation) allows you to do all of those things by outputting current in modulated pulses. The length of the “on” portion of the pulses is expressed as a “duty cycle” from 0% (full off) to 100% (full on). By varying the duty cycle of the pulses you can move a servo or change the brightness of an LED.
The DN9685 duinoNode is a PWM I/O expansion device, for use with most microcontrollers (such as Arduino, ESP32, etc) and microcomputers (Raspberry Pi, etc.). Built on the PCA9685 LED controller chip, this board provides 16 12-bit PWM ports for micro servos and LED devices that can be controlled via I2C. The DN9685 is fully compatible with other PCA9685 devices, and with standard PCA9685 code libraries.
What sets this board apart from the competition is unique design features that address the needs of model railroading. For starters, in addition to traditional servo headers, we’ve included wire terminals for each port allowing easy connection of LEDS and other wired devices. Having connections for both servos and wired LEDS, or other PWM devices, one board can — without modification, soldering or custom connectors — power a complicated scene like a crossing with both flashers and servo-controlled gates, plus lighting and other features for the surrounding environment.
Key Features include:
- This board is designed for lighting and automation needs of a layout, so it has both plug-in servo headers, and wire terminals for each port. On any port, you can either plug in a standard micro servo OR attach an LED, or other wired device, via the wire terminal.
- Our wire terminals are the “rising cage” type that work well with a wide variety of wire types and gauges, including magnet wire. Ground terminals are provided to complete LED circuits.
- We’ve made this a 5 volt device, since that is the voltage required for servos, which simplifies connections and allows a single power input with MOSFET polarity protection.
- It has 220 ohm limiting resistors on the PWM outputs, so most LED devices can be attached without additional resistors.
- Each board has a 5 Amp power rail to facilitate power sharing between boards. Attach one board to your main power source, and up to 10 more boards can be chained and share power. Each board has two sets of power terminals which can be either power in or power out as you decide.
- This board gives you control over the output enable function of the PCA9685 chip. You can select, via jumper, whether OE is enabled or disabled when the board powers up. From there, you can control OE via an additional pin on your MCU. Unlike other boards on the market, OE on this board controls both the output from the PCA9685 chip and the 5v power supply to the servo headers. In this way, servos are fully disabled until OE is enabled.
- Dip switches are provided for easy setting or changing the I2C address of the board
- No soldering required to use this board, ever. The board is a little larger than products used in robotics making it easier to work with underneath a layout. Flexible connectivity makes it easy to modify wiring and change connections in the future.
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