Upgrading a Web based DCC control station

This is a new article being developed by Eric Timberlake

This is a WORK IN PROGRESS! Do not trust anything as "real" just yet!

A DCC WiFi receiver upgrade

A recent SIG meeting featured THIS device, a functioning steam locomotive throttle that requires actual input from the operator to run the locomotive all packaged in a clever 3D printed enclosure with levers for the Johnson bar and such.

(include information about IOS/Android DCC control app here!!)

Project Reception

All Geoff had done was HO sized applications via track delivery, but the G-Scale crowd at the April 2023 MRT SIG meeting was all very excited about the project and the idea of adapting it to G-Scale use.

Problem is, we need 3-6 amps of DCC modulated power to run our big locos and loud sound cards.

I volunteered to see about updating the receiving end of all this work by Geoff and others to support a G-Scale sized load.

Research

My first step was to research what is called an "H-Bridge" and some design theories behind it. I learned that when using MOSFET as a switch, a thing called "Gate Capacitance" is your enemy.. What that describes is the time required to TURN OFF a typical MOSFET and how if you're not careful it's easy to turn on BOTH SIDES of the bridge for very brief periods which will lead to overheating and eventual failure of the output stages.

Reverse Engineering existing product

I spent LOTS of time digging through SPEC sheets, but then I realized I had an actual example of what I want to do sitting right on my bench.. An Airwire 900 CONVERTER-60 - the EXACT THING I want to duplicate, except it's receiving a signal via 900MHz radios vs. WiFi frequencies at 2.4Ghx.

They use a device called a BTN8982TA : https://www.infineon.com/cms/en/product/power/motor-control-ics/brushed-dc-motor-control-ics/single-half-bridge-ics/btn8982ta/

They use a Texas Intruments micro-controller and an off the shelf 900MHz receiver module, so there's not really much to reverse engineer here.

Sample Application

And reading the SPEC sheet, I found this device has built in circuitry to prevent the overlap condition mentioned above from happening, and THEN I found Infineon had done almost all the work for me in terms of a "sample application circuit"! Talk about helpful!

Adapting to the D17 ESP8266 code

So, now I can take all these typical concepts and start working on a schematic that integrates a everyday ESP8266 "Wemos D1 Mini" into a "wifi" receiver that outputs DCC capable of up to 6-10 amps or so.. This example application lines up VERY nicely with Ulysse Delmas' ESP8266 code base for a 754410 half bridge chip - we'll just sub in the new parts and you end up with a viable circuit that SHOULD work!

The BTN8982TA half H-Bridge features "IS" or Current Sense out, but we can't really use it:

1. A: I didn't write the D17 code, and I'm not about to change it...
2. B: The Wemos D1 Mini only has one Analog input, and we'd need two, so...

We'll just leave the IS outputs open and forget about that feature for now.

I also skipped the reverse polarity protection in the example, and likely will delete some of the power supply bypass capacitors as the Wemos D1 Mini actually has most of these parts already on it.

Make a circuit board

Now that we have selected the parts list, or Bill Of Materials, designed a schematic and assigned what is known as a "footprint" to all the parts we can consider trying to craft a circuit board to hold it all...

TBC - To Be Continued... Check back soon-ish - or not..  ;-)