Here is an expansion of my R/C to DCC circuit. I now have all six channels of a cheap 2.4Ghz Radio Control System driving a 2Amp Economi DCC decoder. Throttle stick drives the speed, the other sticks trigger the bell, horn and other sounds. I have one of the switches doing the direction. The DCC amp can drive a 4A load with peak to 5A so more than enough for most G scale Here I’m driving a single USAT motor block. Still have a couple of small issues in the firmware but for the most part it works quite well. I am going to try to finish this off over the next few days and design a PCB for it.

I’ve been neglecting one of my main investments and interests, my airplane- 172ME.

So I spent some vacation time working on sprucing her up. Put in some new plastic trim and painted the headliners. New seats and wall panels are coming in June. I guess next pass will be an owner assisted 100hr with Dan the mechanic man. I need to take out everything to the bare metal on the inside and put it all back in new. And then do something about the paint on the outside. At least touch it up. Needs new seat belts too, and ADS-B. Always something 🙂

Ok, not engineering but eh. Here are my new Brahma Chickens. Ordered 18, they sent 21. All arrived fine and healthy. These will grow into rather large birds, the males can reach 12-14 lbs. I’m not sure why I like chickens but I do. This is the first time I’ve gotten all one breed of chicken. Last shot IS engineering I guess- my fortress Chicken Coop with automatic aluminum door, all solar powered.

Got my prototype to run first pass. This is a motor driver chip that I have wired to convert logic level DCC to 14v 5A DCC. I was working with the LMD18200 but that sucker was $16 from mouser! Ouch. And it only did 3A. This is the L298N which is only 3 bucks from Sparkfun. Big difference! Now I just need to layout a PCB and get it off this breadboard. Sometimes rainy days are not so bad…

I’ve been working with the series 1 Xbee for several years in order to control large scale model trains. For those not familiar with this device, the Xbee 1 is an integrated package that communicates on the 802.15.4 IEEE wireless network. This is the base level network, only the MAC layer, no mesh or other high level network layers. I have the device configured in ‘API’ mode, which means it accepts standard format messages with a header and checksum and passes those out to the network. It’s actually very simple- all of the nodes are on the network and any node (via a 16 bit address) can talk to any other node. So this means I can do anything with this from controlling trains to controlling turnouts or animations or sending back telemetry from the locomotives, etc, etc.

Well, it turns out that the 802.15.4 protocol is rapidly becoming one of the standards used in IoT, Internet of Things. From what I have read, it has about 65% or so of the wireless IoT market share. So I’ve been working on ways to control large scale trains with this in mind. I’ve had quite a bit of success with this and now one of the outputs of my control widget board can generate DCC messages to directly drive DCC decoders (up to 3Amps for now, I have a 5amp version I’m working on).

This is an open-ended algorithm, it can generate the proper DCC bit stream from any input of hex bytes. This lets me keep the network traffic down as the widget generates all the timing for the DCC signal. I only have to pass the basic commands over the network which keeps everything nice and small and fast.

Anyhow, here is the latest incarnation of the DCC 802.15.4 Widget driving a QSI decoder. This one is installed in an Ariso Dash9. Unlike previous designs this one has only one connection- the DCC output from the widget. This is fed to a ‘DCC amplifier’ that then drives the QSI DCC decoder. A 14.8v 5000mah battery provides the power.

This was an interesting install for a couple of reasons. First, the decoder is ‘plug and play’, I disconnected the track pickups and plugged the decoder into the socket- everything just works, no rewire of the motor blocks or LEDs! Very cool. The outputs of the DCC amplifier then drive the decoder directly, no motor controllers or relays or anything.

The second reason was the software. I’m not sure about the vintage of the QSI firmware but it was not happy with the extended DCC packet format for the throttle messages. So I branched the software and made a version that only sends the base DCC packets. I put the QSI into ’28’ step mode and all was good. I wasn’t particularly pleased by this but what can you do eh? I still need to do some CV tweaking for the momentum and braking but it’s working well.

At some point I will be trying out the new WOW large scale decoder and the Economi 400 to see how they react to the extended packets. I’ve played with the Econami 100 and 200 decoders so I assume the 400 will behave in a similar way. Nevertheless, I’m thinking I will need to re-work my firmware to include both the extended and the base level DCC packet generation. That is the official standard according to the DCC docs so I should support it.

Above is the basic circuit. On the left is the DCC driver, then next assembly is the 14v to 5v stepdown power supply which can deliver 2.5 amps of 5v (for servos, etc) to the IoT Widget. In the middle with the Xbee is (obviously) the Control Widget. On the right is speaker #2, I’ll be routing most of the horn and bell sounds to this one with the big sub in the engine compartment handling all of the prime mover sounds.

A picture of the main speaker driver. This is a tangbang full range speaker with passive radiator. Really nice bass from this unit. Here is link to it: tang-bang-speaker

Here is a shot of the ‘terminal’ (Hand held controller) I’ve developed for interacting with the IoT 802.15.4 network. This one is a back-lit alpha numeric display which works great- I can see it out on the layout as it gets dark at night.

Above is a new design I’m trying out- This is a full color graphic touch screen that has tons of features. It incorporates a usb programmer port, a speaker and a built in lipo charger circuit. I just can squeeze it into the same case as the alpha display so we shall see how it goes. Work in progress.

This is the widget driving an Econami 200. Since it’s only 2 amps, I will probably be using this in a critter or railcar of some type. Right now all I have it hooked to in this video is the speaker.

Here is a video of the widget controlling the QSI. I think all the firmware changes are in so I’ll be buttoning up the unit and taking it out to the layout soon for some real world testing. I may go ahead and run the servo lines out just so I don’t have to open it back up when I put servos on the couplers.

I continue to refine my control widgets. Here is the latest incarnation. I’ve shrunk the footprint down and boosted the clock speed to 12Mhz. This module ties into the 802.15.4 network via Xbee. I’m using the Series 1 not the Pro and Zigbee. I’m not real hip on the Pro Zigbee Mesh, it seems overly complex compared to say the Synapse SNAP mesh network.

Anyhow, according to what I’ve been following on the IoT blogs and sites, 802.15.4 has about 65% of the IOT market so I’ve decided to concentrate in that direction.

Basically, this module allows you to control things like servos and digital outputs, plus it gives you a DCC logic level signal output as well. Feed that into a motor driver like the ones from Pololu and you have a nice robust DCC implementation that is network based, rather than the point to point of Bluetooth or R/C.

I’m also looking into another implementation, via the Synapse RF266 SNAP module. I had initially though I could somehow make the RF266 work with the Xbee Series 1. While I think it’s technically possible to do this, the effort involved is quite extensive. Instead, I think a minor hardware platform will make things easier and actually, more flexible, so I’ve started down that road. Essentially, I’ll use the two serial ports on the Attiny to link the two modules together. With the right firmware I should be able to hang a Xbee Series 1 network off of the SNAP network for all sorts of diabolical mesh network fun. 🙂

P1050050

P1050053P1050049

One thing that I have not been real happy with as I build out my control network, is the hand held controller implementation. I had hoped this design would change that but after I’ve played with it a bit I don’t think so.

It features a uLCD-32 smart touch screen display unit, a large aluminum knob and four tactile hardware buttons. The display unit is a very full featured device including a Lipo battery charging circuit! Very cool. The custom graphics chip and language are very powerful and more importantly FAST. This will take all the UI load off the Xbee/Widget device. More info is here – Serial TFT Color LCD

So, I think I don’t like this one either. I’m going to scavenge the LCD and try to fit it in the case I’ve found for the alpha numeric monochrome unit. It’s a tight fit but the quality of this display is just too good to let it go to waste. I’m finding I like the off the shelf case I have (I bought two) better than I thought. I have somewhat large hands so I can hold it in my left and turn the knob with my thumb.

So this one is defunct now. More to come on this project later.

synapse

Well, I can’t believe I have not seen this module before. I may have but discounted it because it is about $11 more than an Xbee Series 1. However, the features in this module are very compelling, you really get a LOT of extra power and features for that $11.

This Synapse RF module-in-an-XBee-Pro-form-factor features OTA (Over-The-Air) speeds up to 2Mbps, maximum 1.2km (4000) range and a chip antenna for compact installation.

This particular RF module includes a user programmable (via python-based scripts), embedded ATmega128RFA1 microcontroller that can be programmed for all kinds of applications including remote sensor monitoring, remote control, or peripheral activation.

Features:

  • XBee Pro pin and footprint compatibility
  • Very high communication speeds (250kbps to 2Mbps)
  • Up to 1.2km (4000′) foot range (line-of-sight)
  • Built-in Python interpreter (Who needs additional microcontroller? This one has one built-in!)
  • Wide low voltage TTL operating range (2.7 – 3.6V)
  • Ultra low power consumption mode (1.18µA. Not mA, but µA!)
  • 15 GPIO, featuring
    • 4 10-bit A/D inputs
    • 4 PWM Outputs
    • 7 Interrupt capable pins
  • 128k flash, with 58k free for over-the-air loaded user programs
  • Communication options include I2C (TWI) master mode, SPI (3 & 4 wire, master mode), 1 UART
  • Low power capabilities (2.3uA sleep current)

More:

  • Embedded ATmega128RFA1 on-board
  • 1 UART port (pin 2, 3) for LVTTL (3.3V) serial control or transparent data
  • Able to be configured to wirelessly program Arduino Uno & Mega 2560
  • Socket-able (2mm spacing) or solder-able
  • SNAP, instant-on, self-healing, mesh network operating system
  • 802.15.4 Protocol at 2.4GHz
  • I2C communication (Pins 9, 13)
  • SPI communication (Pins 18, 19, 20)
  • 128k flash memory (56k available for user applications)
  • Can be used stand-alone (no additional microcontroller required)
  • Low power mode of 2.3uA with internal timer running
  • Supply voltage: 2.7V~3.6V
  • Transmit current: 130mA (Typ)
  • Receive current: 25mA
  • Sleep current: 2.3uA
  • Operating temperature:-40°C ~ 85°C
  • Power output: 20dBm for best-in-class range
  • FCC certified on all 16 channels (2.4GHz)
  • Spread spectrum (DSSS) technology resists noisy environments