gunrunnerjohn posted:Discussions keep coming up about a signal control board, especially now that there seems to be several choices for cheap O-gauge track signals.
That being the case, I figured we'd start a new thread and see what features might be desirable in something that would be in kit form for users to build. I'm thinking we'd sort out a feature list and then whittle it down so that it could be made in an inexpensive manner with common parts. I'll start with a few attributes and we'll go from there.I'm thinking a thru-hole PCB design with a inexpensive parts BOM that can be easily assembled by most folks that can solder. Having a board greatly simplifies the task of assembling one or a number of these.
Let's all join in and toss some ideas around!
I have an Arduino Nano configured to do some of this. I use it with the WeHonest 2 and 3 aspect signals. It is sensitive enough to detect your fingers touching the ground and signal rails. (I have it currently set for 3 rail operation. 2 Rail would need to be converted for current sensing instead of ground sensing.)
- Low cost! (one of the primary objectives)
About $3 for the Arduino, and $1.50 for the breakout board it plugs into to have a screw terminal on each pin. So $4.50, and each one controls two signals.
- Multiple types of input, i.e. IR, insulated rail, etc.
I use it with insulated rail. I do use IR detectors with the nano for switch anti-derail. It would be pretty easy to add software to detect either ins rail or IR, and use a toggle switch on one of the digital pins to flip which one is being utilized.
- Drives two and three aspect signals with appropriate delays for yellow & green (programmable?)
I do a PWM fade-out/fade-in. The WeHonest signals have a single resistor connected common anode, so you cant have the multiple led's lit at the same time. But the fade-out/fade-in under software control looks pretty good. (It looks hideous on a video at 30 frames per second due to the strobing effect.)
- Drives road crossing crossbuck signals directly.
It could drive a servo-driven crossing gate or wigwag directly without any issue. It would need an fet driver if the mechanism used anything that drew more current , like electromagnets, or if we wanted it to drive the sound.
- Direct drive of LED or incandescent lamps.
Led's are direct drive. Incadescents would need to have logic level fets on the output pins.
So, you could basically take this setup, add a few fet's for higher current draw items like incadescents, and be pretty close.
One nice thing about the arduino microcontroller is its ability to add pullup resistors under software control, without the need for discreet components. That really comes in handy for ground sensing devices.
For my future large layout, I plan on some Arduino Nano's simply becoming block detectors (8 blocks detected per Nano) with these block detecting Nano's communicating to an ethernet nano which sends the block data back to a main system, which then can software control the aspect signals from that data. This would allow easier wiring of the signals, as I wouldnt need to wire the blocks to each signal.
