My enormously complicated, enormously fun DC throttle project

[mmagliaro]

John,
I designed all the boards myself using KiCAD (main throttle, receiver, transmitter, pulse generator, and a few other little ones that are only used
for the "power pack version").  KiCAD is awesome, free, and VERY intuitive.  It also includes a massive library of 3D cad models of the actual components, so you can have it render you a 3D vision of what the actual populated board will look like (and any models it doesn't have, you can usually download from sites like Digi-Key or Mouser on the page from the component, or from various other component CAD sites like GrabCAD).
It uses the netlist from the schematic and enforces it when you design the PCB, so you won't screw up and leave something unconnected, or short traces to each other that shouldn't be, and so on.  In my case, I already had the schematic from another tool, so I did not redraw it in KiCAD.
Instead, I used somebody's "WireIt" plug-in to KiCAD which let me specify the nets ("what-connects-to-what") by hand (but graphically, by clicking components on the PCB).

It spits out the Gerber files that PCB makers all need, and many of them will just take a zip of your KiCAD project directly.

As for where I got the boards made, I started by using aisler,net.  They are based in Germany, but have a manufacturing plant in Houston, so the labor is US-based for US customers, and so is the shipping (and no import duty).  They cost about $8/board.  Turn-around time was very slow, about 3 weeks, but I was willing to put up with that to keep the labor US-based.  But I became frustrated by their poor customer service.  Inquiries can only be made through public message forum.  It took days for one of them to reply.  And my question about making boards with a black silk screen was reponded to with a confusing, and completely wrong, set of answers from more than one person at Aisler.  It took weeks for me to get a straight answer out of them (and the answer was ultimately, "No, we can't do any color but green").

Soooo..  much as I did not want to, I was forced to go to a China supplier, JLCPCB.  I tried about 20 US companies, and they either wouldn't touch a small job, or couldn't do black, or wanted about $25-$30 per board, which is so oppressively expensive that it's out of the question.  JLCPCB does them for about $2/board.  But on a 5-board order plus the shipping from China, you end up spending about $35, so $7/board is the end cost.  Of course, on a larger order, the shipping would be much less of a factor and the cost would come down.  The other thing about JLCPCB is that they are stunningly responsive.  My questions were almost always answered instantly through a chat window, no matter what time of day or night.  One time, they even had to look at my board layout to answer the question, so they grabbed while we were in the chat window, and opened the gerber files to check something before answering my question.  It takes about 8 days from the submitting the files to when I have the boards in my hand, which is amazing.

[mmagliaro]

Here's a 3D render of the maint throttle board from KiCAD:
The posted image doesn't do it justice.  You can rotate and zoom this view in the tool, and all the letting and edges are rendered crisply
and accurately.  You don't appreciate how important this rendering is until you use it.  Then you immediately see problems that you won't see
just by looking at your PCB layout, like components that are positioned so as to make it clumsy to insert them, or terminal blocks there it's
too hard to get the wire into them because of some nearby component, or things that get hot being badly placed near components
that really don't like heat.
The rendered 3D components are all good likenesses of the real parts.  Those relays are not, because I didn't bother to hunt down the
correct CAD file for those.  They are just generic relay models with the correct footprint and pin-out.

[mmagliaro]

Just to let folks know, I have not "dropped" this.  I am in the process of building one and timing myself to see just how long it actually takes to build, so I can add that to the cost of parts and come up with how much it would cost to make one for somebody else if they want one.  I also have a complete technical guide written that explains how all the sections of the circuitry work, has a complete parts list with schematics, and an illustrated assembly guide.  My goal here was to build it and have it documented, whether I ever build any for other people or not.  I don't want all this work to disappear when I disappear someday, like what happened to the GML throttle.

[mmagliaro]

After extensive design testing and updates, here it is...

To be crystal clear.  This is a DC THROTTLE.
For anyone who missed my previous mentions of this and the brief video demo I showed on YouTube,
- I fully realize DC control is in the minority
- However, I also realize that periodically people ask where they can get a DC throttle because so many
makers have gone by the wayside
- I started out just building a nice clean update on a "transistor" throttle I built in the 70s (which still controls my layout),
but got carried away and it became an almost industrialized item

Next week, I still start a thread in the "Product Announcements" in the event that anyone has an interest in owning
one of these.  A few people inquired when I showed it back in February.

==========================

FEATURES:
- Works as a stand-alone analog throttle with conventional controls (speed pot and switches to control direction, momentum on/off, pulse on/off, overload reset)
- Capacity up to 3A (and it's an honest 3A.  It can do 3A at any voltage up to full.)
- Track voltage is 0-12.
- Sensitive, accurate, fast-acting overload detection (not a slow, clumsy fuse or breaker).  If I set it to trip at 3A, by golly,
it is going to trip within a few percent of 3A, and it will do it in less than 50 mSec
- Because people asked: the speed control is a standard single-turn dial.  No "spin it round and round" to increase or decrease speed, and no "up/down" speed pushbuttons.  While I am building these with a SPDT toggle for direction, you can connect two momentary contact pushbuttons just as easily if you are just using the main throttle board directly.  I won't be building the wireless hand-held controller with pushbuttons.  The circuit board and enclosure openings are all set up to accommodate the toggle.

- Can also use an optional wireless receiver and transmitter for full wireless walk-around.
- Each transmitter can be set to any of 10 different "channels" so you can have more than one main throttle board
on the layout, each set on a different channel, just like having separate DC throttles or power packs as "cabs" and they
can all be separately controlled by different walk-around hand-held controllers.
- Wireless hand-helds work off a 9v battery.  I estimate the battery life at 3-4 months if you used it for 2 hours every day, but I don't actually have any total measurements on this yet.  I'm estimating based on current draw and the mAh life of an alkaline 9v battery.

Technical Documentation
I created an exhaustively detailed 100 page technical guide that includes the theory on all the circuits, full schematics, full part lists with exact part numbers and sources (i.e. Mouser, Tayda, Jameco, others), and assembly instructions (if somebody were to try to build one themself).  It is as much for my own reference as for anybody else.  Anybody can have one if they want it.  Just PM me.   But it is 80MB in size, so I'm not exactly sure how to get it to you.   It has a lot of photos and drawings, but I warn you, it is an uber-nerd electronics manual.

COST
- I compiled a complete cost of materials, and also timed myself building everything.  So in the event that anybody would want one...I came up with these costs assuming $20/hr for my time (which is ridiculously low, I know...  my kid makes $16/hr working at KFC!):

Just the main analog throttle board $200+ shipping - I can provide things like toggles and pots for the speed and controls.  If you want them prewired with connectors to plug into the board, that will be extra, just based on the hours it takes to prepare them.

The Main throttle + wireless receiver + wireless walkaround transmitter: $335 + shipping

==============
Here are photos of what it looks like:
Main Throttle:


Throttle + receiver


Throttle + receiver + transmitter

[peteski]

Very impressive!
Now you just have to  come up with a catchy model-railoradee name. Maybe retro-style, like something from the 50s that ends with "matic".    Thrott-o-matic?    Or maybe a more modern name that reflect the unit's complexity?  Compu-throttle?   Digi-pak?

I know, I'm being silly. 

[jagged ben]

What did the approximate wireless range turn out to be?
What frequency does it use?

[mmagliaro]

I am travelling, so I won't be able to address questions properly until Tuesday.  But I can tell you I currently use either 433MHz or 315MHz for the frequency.  I can buuld it with either and have tested it.  There are little OOK modules out there for 868 and 915 MHz as well.  They might work, but I have never tried them.  I have not done an exhaustive range test yet.  It definitely works up to 30 feet through multiple walls, but I need to test more to see how far it can go, especially line-of-sight.  I will be reporting in here as I test that. 

[mmagliaro]

Very impressive!
Now you just have to  come up with a catchy model-railoradee name. Maybe retro-style, like something from the 50s that ends with "matic".    Thrott-o-matic?    Or maybe a more modern name that reflect the unit's complexity?  Compu-throttle?   Digi-pak?

I know, I'm being silly. 

You think YOU'RE being silly... my working title for it has been the "MaxCow Throttle"... and I may not change it.   

[peteski]

You think YOU'RE being silly... my working title for it has been the "MaxCow Throttle"... and I may not change it.   

Now that you mentioned it, I'm not too surprised.
I seem to recall that you used that name in the past - I don't remember where though.  I'm curious as to the origin of that name.

[mmagliaro]

Now that you mentioned it, I'm not too surprised.
I seem to recall that you used that name in the past - I don't remember where though.  I'm curious as to the origin of that name.

I have used "MaxCow" on things before, like my website URL.  It's because it is short, easy to spell, and people will remember it because it is funny (has the word "cow" in it, and as Gary Larsen observed, cows are just naturally funny).
Well, okay, that and... I like cows.

[peteski]

I have used "MaxCow" on things before, like my website URL.  It's because it is short, easy to spell, and people will remember it because it is funny (has the word "cow" in it, and as Gary Larsen observed, cows are just naturally funny).
Well, okay, that and... I like cows.

Fair enough. Do you practice bovilexia when you see cows on the side of the road? 

Gary Larsen? He's brilliant!

[randgust]

I'm interested, but two questions..... or maybe if I just read more I'd figure it out.

DC output - is this a 'pure' DC, or a square/pulse transistor, or otherwise modified output?

Power in - every walkaround throttle I have is set up for DC voltage in and DC voltage out on a 4-pin connector.    I'm having difficulty figuring out what your input power supply is.
If got a collection of conventional wired throttles, some commercial, some home-brew, varying from a pair of ancient CAMA throttles to a pair of PS550 cabtrollers to a pair of home-brew pure DC throttles with internal additional resistors.  Getting rid of the cable here would be nice, so I'm interested.

[jdcolombo]

Hi Max.

Well, it's not enough to get me to switch back to pure DC, but . . .

It's majorly impressive.   If this would have been available back in 1990, it probably would have delayed my switch to DCC by 10 years.  A major part of my switch to DCC in 1995 was to get the wireless walk-around capability that a small company called Digitrax was just introducing.   I'd have ended up with DCC sooner or later, but it would have been later.

John C.

[mmagliaro]

Hi Max.

Well, it's not enough to get me to switch back to pure DC, but . . .

It's majorly impressive.   If this would have been available back in 1990, it probably would have delayed my switch to DCC by 10 years.  A major part of my switch to DCC in 1995 was to get the wireless walk-around capability that a small company called Digitrax was just introducing.   I'd have ended up with DCC sooner or later, but it would have been later.

John C.

Heh, yeah.  Well, back in 1990, something like an Arduino microcontroller board was an abstract gleam in somebody's eye.  And there weren't ready-made cheap RF transmit and receive modules no bigger than a postage stamp either.  My purpose, as I've said, was for my own fun, experimentation, education, and the end product of a much nicer DC controller for my own self.  But I am keenly aware that periodically people ask about "where they can get a good DC throttle these days".  So when I was redesigning all this, I did it in a way that it could possibly fill that need if anybody really wants one.  And all the documentation, parts lists, schematics, etc, that I prepared with it are so it doesn't "die with me" if somebody wants to use one or fix one someday, which has happened to other throttle designs.

[peteski]

Max,
Going by the large filter caps, my guess that your throttle can output filtered "pure" DC voltage.  You also mention pulse option and that it can use a "pulse module"  That sounds rather complex.  I'm curious why didn't you just use a simple on-board pulse generator (either made up from discrete transistors or something like a 555 timer IC)?

Back in the day I built the TAT V throttle (from the plans in Model Railroader), and it uses that kind of simple pulse generator. It features adjustable frequency and pulse width, and that really works well to finr tune it to make every motor crawl at slow speeds.  That throttle works really well,