Using the ProMiniAir with DCC Accessories

One of the advantages of standards, such as the NMRA’s DCC standard, is that multiple vendors’ products are interoperable. There are dozens of DCC vendors, and they all “play nice” with each other (mostly).

The purpose of this post is to show you that you can use the ProMiniAir Receiver and Transmitter for more than just controlling locomotives – you can use it for dead-rail (wireless) control of any DCC accessory (stationary) decoder for lights, turnouts, etc., simply by connecting a low-cost ProMiniAir Receiver/Amplifier to the DCC inputs of one or more DCC accessory decoders. Generally, DCC accessory decoders are inexpensive, e.g., the NCE Illuminator for lighting ($22.40 for a 3-pack) or the Digitrax DS52 for turnout control ($20.36 for control of 2 turnouts).

Then you can use one of several transmitter options (that you also use for dead-rail control of your locomotives), including 1) an Airwire transmitter, 2) a WiThrottle smartphone app connecting to a Stand-alone ProMiniAir Transmitter integrated with a WiFi-equipped EX-CommandStation, or 3) any DCC throttle connected to a ProMiniAir Transmitter. All three options are designed to easily set the accessory address and activate the device while simultaneously controlling the locomotive or locomotives.

For DCC accessory decoders, nothing extra is required since the DCC accessories get their power from the DCC output from the ProMiniAir Receiver. Battery power can be used in remote or inconvenient locations. You can also wirelessly configure the accessory decoders, such as the address. No proprietary accessory devices are necessary since dozens of vendors use DCC, a widely-adopted standard that fosters competition and innovation. There is no “vendor lock” wedded to one manufacturer’s “solution.” The videos show how to activate DCC accessory decoders using the ProMiniAir Receiver in conjunction with these Transmitter options. 

An Example

In this example, three NCE Illuminator lighting accessory decoders for connecting LEDs for lighting effects are “daisy-chained” with a DCC connection to the output of an unmodified ProMiniAir Receiver/Amplifier using 14.8V battery power. Their addresses were set to 10 (white light), 20 (red light), and 30 (green light). At the end of the DCC daisy chain is a Digitrax DS52 set to address 30 so that it will activate a Tortoise slow-motion switch machine. So, the throttle selection of an accessory at address 30 will activate both the green light and the switch machine. No additional hardware is required.

Demonstration setup connecting an unmodified ProMiniAir Receiver/Amp to various DCC accessory decoders. Note how multiple DCC accessory decoders can be “daisy-chained” together.

The videos below show wireless control of the locomotive and the DCC accessories with 1) an Airwire transmitter, 2) a standard DCC throttle connected to a ProMiniAir transmitter, or 3) a WiThrottle smartphone app connecting to a low-cost stand-alone ProMiniAir Transmitter integrated with a WiFi-equipped EX-CommandStation.

An Airwire throttle transmitting to a ProMiniAir Rx/Amp connected to accessory decoders while simultaneously transmitting to a dead-rail locomotive with an onboard ProMiniAir Receiver/Amp. Note the activation of the switch motor!
A standard DCC throttle connected to a ProMiniAir Transmitter that transmits to a ProMiniAir Rx/Amp connected to accessory decoders while simultaneously transmitting to a dead-rail locomotive with an onboard ProMiniAir Receiver/Amp. Note the activation of the switch motor!
A WiThrottle smartphone app transmitting to a stand-alone ProMiniAir Transmitter integrated with a WiFi-equipped EX-CommandStaion that transmits to a ProMiniAir Rx/Amp connected to accessory decoders while simultaneously transmitting to a dead-rail locomotive with an onboard ProMiniAir Receiver/Amp. Note the activation of the switch motor!

Additional Information

Each accessory decoder has its method for setting up its DCC address, but this is usually as simple as 1) set the “programming jumper” on the accessory decoder if it has one, 2) turn on DCC power to the ProMiniAir receiver, 3) push a “configuration button” on the accessory decoder (if it uses one), 4) use your throttle to select an accessory, 5) enter the accessory’s address you want the accessory to use, 5) use your throttle to push the button that “throws” (activates) the device, 5) turn off DCC power to the device and disconnect an “activation pin” (if it uses one), and 5) reapply DCC power.

At this point, the DCC accessory “remembers” its address so that you can now use your throttle to select the accessory’s address and push the appropriate button to activate or de-activate the accessory.

Final Thoughts

Well-thought-out standards, such as the NMRA’s DCC standard, are good. I hope you can see that connecting an unmodified ProMiniAir Receiver/Amp to any DCC accessory decoder(s) from numerous vendors is effortless rather than using a limited, proprietary wireless solution for controlling accessories such as turnouts and lights while at the same time controlling your locomotives.

I thank one of my customers, Jeffrey Jackson, for the question that led me to investigate this topic!

Using the Pololu TB9051FTGU and TB67H420FTG Motor Drivers as DCC Amplifiers for Dead-Rail

Based on a Dead Rail Society Facebook post by Rich Steenwyk, I investigated the suitability of using the Pololu TB9051FTG ($11.95, 2.6A continuous, 1″ x 1″) and the Pololu TB67H420FTG ($19.95, 3.4A continuous, 1″ x 1.2″) as a DCC amplifier in conjunction with the ProMiniAir Receiver for Dead-Rail operation. This post investigates their feasibility and shows connection details.

Feasibility and Connections

The Pololu TB9051FTG is 1″ x 1″

The TB9051FTG truth table below shows the proper bipolar operation on highlighted rows. Note the pin values for EN and ENB. Based on this truth table, this device should be capable of delivering bipolar DCC to the decoder.

The TB9051FTG truth table

Connections for the Pololu TB9051FTG are shown below. When connected to a “large” decoder such as the LokSound 5 XL shown here, a current-limiting resistor is required to prevent the TB9051FTG from shutting down. The Negative Temperature Coefficient (NTC) resistor is initially at 1 Ohm, but with increased current demand, it heats up, reducing its resistance and voltage drop to a low value. This solution is superior to a high-wattage constant 1 Ohm resistor CVP recommends for its smaller Airwire CONVRTR receivers.

The ProMiniAir Receiver/TB9051FTG connections

A close-up of the connections for the Pololu TB9051FTG is shown below. Bipolar 3.3V DCC outputs and +5V from the ProMiniAir Receiver are required for proper operation. Note the jumpers that set EN to VCC (High), ENB to GND (Low), and OCC to VCC (High, retry after shutdown).

Close-up of ProMiniAir Receiver/TB9051FTG connections

Example DCC output for the decoder provided by the ProMiniAir Rx/TB9051FTG combination is shown below.

DCC output from the ProMiniAir Rx/TB9051FTG combination

A demo of the Pololu TB9051FTG in dead-rail operation, which will NOT operate with the LokSound 5 XL (5A max) without a current-limiting resistor, is shown below.

Demo of the ProMiniAir Rx/TB9051FTG combination

Now let’s turn to the larger, more expensive TB67H420FTG.

The Pololu TB67H420FTG is 1″ x 1.2″

The TB67H420FTG truth table below shows the proper bipolar operation on highlighted rows. Note the value of PWMx must be High. Based on this truth table, this device should be capable of delivering DCC to a decoder.

The TB67H420FTG truth table

Connections for the Pololu TB67H420FTG are shown below. When connected to a “large” decoder such as a LokSound 5 XL, a current-limiting resistor is NOT required to prevent the TB67H420FTG from shutting down. However, the TB67H420FTG is more expensive and larger than the TB9051FTG.

The ProMiniAir Receiver/TB9051FTG connections

A close-up of the connections for the Pololu TB9051FTG is shown below. As with the TB9051FTG, bipolar 3.3V DCC inputs from the ProMiniAir Receiver are required for proper operation. Note the single jumper connecting VCC (High) to HBMODE that turns on the single-output function. Jumpers between A+/A- and B+/B- deliver the maximum single DCC output of 3.7A. 

Close-up of the ProMiniAir Receiver/TB9051FTG connections

Testing with the TB9051FTG when interfaced with a ProMiniAir Receiver was successful.

Conclusion

Both the Pololu TB9051FTG ($11.95, 2.6A, 1″ x 1″) and TB67H420FTG ($19.95, 3.4A, 1″ x 1.2″) can be configured to deliver full-power DCC to a decoder when used in conjunction with a Dead-Rail receiver such as the ProMiniAir Receiver. They require five connections to the ProMiniAir receiver, including 3.3V or 5 V bipolar DCC outputs. The lower power TB9051FTG does require a current-limiting resistor for some decoders that produce large “in-rush” currents during power on, and the TB9051FTG does not.

The Adafruit DRV8871 amplifier is perhaps a better choice because:

  • Cheaper: $7.50+s&h
  • Comparable output: 3.6A
  • Smaller: 1″ x 0.8″
  • Requires only four connections to the receiver: GND, VPOWER, DCC+, and DCC-

The disadvantage of the Adafruit DRV8871 and the Pololu TB9051FTG is they require a current-limiting resistor for some larger decoders. The Pololu TB67H420FTG does not need this current limiter, but it’s slightly larger and more expensive. You decide!