Integrating the ProMiniAir Receiver with QSI Decoders using Gwire Connections

Users of the QSI Revolution or Titan series of DCC decoders may want to take advantage of these decoders’ built-in Gwire connections for radio control but cannot find the discontinued Gwire receiver. This post describes how you can use the ProMiniAir Receiver as a “drop-in” replacement for the Gwire receiver so that you can control the locomotive with the following radio-control throttles:

  • CVP Airwire throttles such as T5000 and T6000
  • NCE’s discontinued Gwire throttle
  • Our ProMiniAir Transmitter
  • Stanton Cab
  • Tam Valley Depot DRS1 transmitter

Integrating the ProMiniAir Receiver with the QSI decoder’s Gwire capability is easy.

Introduction

I strongly recommend you review Greg Elmassian’s excellent post, “QSI AirWire & GWire cab.” It deals with using the Gwire receiver with various QSI decoders, which have a built-in flat flex cable (FFC) plug initially designed to connect to the discontinued and now hard-to-find Gwire receiver.

The QSI Titan FX-DO decoder is an example of a QSI decoder equipped with a Gwire flat flex cable (FFC) plug.

The ProMiniAir Receiver is highly compatible with the Gwire receiver and is somewhat more flexible with more channels and DCC-based reconfigurability. The ProMiniAir Receiver also has a smaller footprint (1.1″ x 0.76″). The modular design approach of the ProMiniAir makes it feasible to take full advantage of the QSI’s Gwire capability to use the ProMiniAir without an additional amplifier.

Integration of the ProMiniAir Receiver using Gwire Connections

The only additional item required is a Parlex HF05U-03-ND 5-position flat flex cable (FFC, 5 Position, 1.00mm conductor spacing, 3″ length, one side connector on both ends), found at Digi-Key here, that plugs into the QSI Gwire plug. Other brands of 5-position flat flex cables are available, notably from Molex.

The Parlex Flat Flex Cable (FFC) 5Pos 1.00mm, 3″

The ProMiniAir Receiver is easily connected to one end of this cable by soldering 30 gauge wires that match up well with the dimensions of the flat flex cable, as shown below.

The soldered connections join 30 gauge wires to one end of the flat flex cable. Only three connections are required: GND, +5V, and DCC.

The other ends of the 30 gauge wires are soldered to the ProMiniAir Receiver, as shown below.

The three 30 gauge wire connections to the ProMiniAir Receiver. Optional connections to an LCD were soldered in place for diagnostic purposes, and these LCD connections are NOT required for final operation.

No DCC amplifier is required because the QSI decoder creates DC voltage from its onboard rectifier. The QSI Gwire connections provide the +5V/GND needed to power the ProMiniAir Receiver, which sends 3.3V Logic DCC back to the QSI decoder.

The QSI decoder must be configured to accept DCC from the Gwire connection by setting “indexed” CV56.1 to 1. This means first setting CV49 to 1 and then CV56 to 1. See Greg Elmassian’s excellent post for more details. Once the decoder accepts this setting, it will only respond to DCC from the ProMiniAir receiver until the decoder is reset, as Elmassian’s post described.

My only addition to Elmassian’s information is that a firmware update may be needed before the decoder will “accept” this setting. I could not successfully update CV56.1 on a QSI Tital FX-DO I used for the testing shown in this post until I updated the decoder’s sound file.

Demonstration

The photo below shows the demonstration setup.

Demonstration setup

The Digitrax DCS52 DCC throttle supplies Track Right/Left DCC, which only powers the QSI Titan FX-DO and the ProMiniAir receiver via the Gwire flat flex cable. The Airwire T5000 throttle will then transmit DCC commands received by the ProMiniAir Receiver, sending 3.3V Logic DCC back to the QSI Titan FX-DO that controls sound and the motor. DCC commands from the DCS52 DCC throttle are ignored.

Below is the video demonstration

Demonstration of the ProMiniAir Receiver using the QSI’s Gwire connections. No additional amplifier is required. Note that the decoder is responsive only to the Airwire throttle. The motor displays an observable “jerk” when changing directions.

Wrap-Up

I have just recently started using QSI Titan decoders. They are challenging to find but produce fantastic sounds and are very flexible. The modular design of the ProMiniAir Receiver makes it very simple to take full advantage of the QSI decoder’s Gwire capability. I provide the Gwire-compatible ProMiniAir Receiver (including the cable) for $19.99+S&H on eBay here. Plug the flat flex cable into the QSI decoder’s Gwire connector, program CV56.1=1, and you are ready to go with radio control!

My thanks to Greg Elmassian for his very useful posts.

Author: Darrell Lamm

I earned my Doctorate in Physics from the Georgia Institute of Technology in 1982, and before retiring in 2019 I worked for 37 years at the Georgia Tech Research Institute. My last position was Chief Scientist of the Electro-Optical Systems Laboratory. Like many people, my love for model railroading began at an early age, and I rekindled that interest starting in 2017.

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