Large Scale Central

New RC Train Control

Electronics Power and Sound
#41

Thanks for the feedback. I tried to make operating multiple locos as easy as possible. I’ve added features I have always wanted on a remote control system.

I’m still working out a few things, including providing for multiple transmitters. I have two approaches I’m testing. The testing is what takes time. Thank goodness testing is fun!

I’m leaning toward making a kit which would have most of the parts but somethings would need to be purchased elsewhere such as the transmitter case (Radio Shack $4.99), and motor controllers (Pololu $35). There will definitely be some assembly required. I may offer boards that have parts already soldered in place. I have worked hard to keep the boards easy to assemble but some soldering skill is required.

I am close to having a few people user test the systems for me. I’m trying to decide what aspects I want them to test, the full assembly or just operating the final product. I’m leaning toward operations right now to insure I work out any software bugs. I expect it will be about two months before I feel comfortable making a kit.

#42

Let me know when you have something you want to test as far as a kit. Would be glad to purchase and try out. Building and fixing electronics use t be a part time job for me - fixing circuit boards and other computer equipment, so putting it together, soldering etc. is not a problem.

#43

I am working on one of the last features on my list, support for multiple channels (10 to be exact). Right now I have two transmitters each controlling a different set of locomotives. So far, so good, no interference problems. I will set up one more transmitter and make any tuning necessary to the radio protocol. This will allow people to use several of the systems together. It also maintains the fail-safe for each transmitter, i.e. if one of the transmitters is turned off then its associated locomotives will all shut down.

#44

Russ,

Are you going to include a battery saver in the transmitter, on that will shut down the transmitter if it hasn’t been used for a while?

#45

My original design specification required a fail-safe. Shutting down the transmitter will shut down the locomotives. I may make a provision to turn off the fail-safe and allow the transmitter to go into a low power mode of some sort but that didn’t make the current short list of features I’m trying to complete. If the receivers don’t hear the transmitter within a five second period (which can be changed) then they will shut down.

Right now I’m using a 9 volt alkaline battery to see how long they last. It would be quite easy to use a rechargeable 9.6 volt pack for marathon railroading sessions. I also have an external power plug I use on the prototypes.

#46

Hi Russ -

That really looks nice. Clean board, nice display, and a good looking face using common components. Good job !

I like your fail safe idea over the power saving function. Especially on large layouts where trains move fairly fast, it’s good to know that when you press the stop button the loco is going to get the command. So long as you can turn of back lighting on the LCD, you should get pretty good life from a 9V without having to power down when idle. Could always replace the transistor battery with a rechargeable pack if battery cost becomes an issue.

Is the pot the speed control ?

#47

Thanks. The transmitter case graphics are done on a laser or ink jet printer with a laminate on the front. Very easy to do and makes things look professional. I’ve even been caught in the rain and no damage to the label. I really wanted to have a fail-safe for the locos. Especially battery because you can’t just turn off track power and have them all stop in an emergency! There is also an All-Stop button that sends a broadcast data packet that all locomotives (on that channel) will respond to and stop immediately. The backlight for the LCD is controlled by hitting 7 on the keypad. In daylight you don’t need it at all. The backlight draws about 15mA when on. The nice thing about the Radio Shack project box (6"x4"x2") is that it will hold a fairly large rechargeable battery and still fit comfortably in your hand. BTW, I now have 10 channels supported so that as many as 10 people could each be controlling 32 locomotives. There may be interference problems with ten but so far three transmitters work with no problems at all. I have assembled two versions of the transmitter having different placement of the throttle. The throttle by the way is a rotary encoder, not a potentiometer, that is how I can change between locomotives and not have them jump to the previous locos speed. Here are pictures of the two transmitter versions so far. Transmitter with throttle on the right side (could make left):

(http://i68.photobucket.com/albums/i27/rmcintir/Robotics/HPIM2990.jpg)

Transmitter with throttle on the front:

(http://i68.photobucket.com/albums/i27/rmcintir/Robotics/HPIM2989.jpg)

I prefer the throttle on the side, more comfortable to operate. The front mounted throttle works fine and if I had started with that version I probably would prefer it instead. The reason the side throttle transmitter has a plug is that it is undergoing long term run testing to insure it can run for days without a problem. I don’t have any batteries that will last that long.

#48

I like the failsafe, too. I find it very frustrating to find the transmitter has turned itself off just when I realize that the bridge is out!

Russ said:
If the receivers don't hear the transmitter within a five second period (which can be changed) then they will shut down.
Does the transmitter continuously update the receiver automatically?
#49

I am glad to hear the fail-safe was the right direction to take. I built the system the way I wanted it to work and later took into account what other people wanted. All radio communication is one way, from the hand held transmitter to the locomotive and accessory receivers.

Yes, the transmitter updates all the locomotives frequently. If for some reason a locomotive stops it will get an update to start again based on what the transmitter had it doing last. Here is an overview of how data transmissions are sent to the receivers:

Every 2 seconds the transmitter sends out an update to the currently controlled locomotive, direction, speed, accessories, etc. At the same time it also updates one of the 31 other locomotives not being actively controlled and increments the second locomotive number. Two seconds later it does the same thing but updates the next uncontrolled locomotive. About every 60 seconds all the locomotives receive an update whether they are actively controlled or not.

When changes to speed, direction or accessories are made to the currently controlled locomotive they are sent immediately. During this transmission one of the 31 other locomotive is also updated using the procedure outlined above. If you are actively changing speeds on a locomotive you will update all the locomotives being controlled more frequently than the 60 second cycle.

If the all-stop button is pushed a broadcast to all 32 locomotives is sent which immediately stops them.

Since I just added the ability to have multiple channels I need to do quite a bit of testing for interference. I may find out I need to modify some of the updates outlined above to insure multiple transmitters don’t step on each other. The data packets are sent so quickly that there shouldn’t be a problem but only testing will tell. As I said, so far 3 transmitters seem to work fine together so far. I haven’t built enough transmitters to test more.

Oh, lastly, the 100 non locomotive accessories for turnouts, lights, etc. are always set to channel 0. Since there will only ever be one railroad being traveled at a time. That way all transmitters can control accessories on whatever railroad they visit.

#50

So far the channel testing has gone very well. I left the systems run all night in a test harness with no errors and no interference. I still need to get them out in the field running together. That will hopefully happen very soon.

Today I added the ability to quickly change channels for each locomotive. Originally I had channel changing bundled with the features of speed, Back EMF and accessory settings. Now it is very easy to change channels for locomotives without affecting the other features. This makes it easier to use with other Cab Command transmitters.

Just for grins I put in a a motor controller that does not provide feedback. The software adjusts and allows it to run like a normal non Back EMF locomotive. You know, the normal, crank it up then back it down to get the slow speed you really want, at least until it bogs down again. I think it will make a great demo locomotive. :slight_smile: Bad thing about that motor controller is that it does not have good overvoltage and overheat protection compared to the new one with BEMF. I need to be careful with it.

#51

Going to run the system again on my friend’s all battery layout tomorrow. I was inspired to use a 19.2 volt Craftsman power tool battery since Bob had shown me that trick last visit. Here is a link to fitting it with no permanent modifications into a Bachmann caboose: http://www.gscalemad.co.uk/forum/index.php?showtopic=5586

#52

Here are some videos of today’s battery power railroading:

First overview of B&D railroad:
http://www.youtube.com/watch?v=X_n4dA1ooQ4

Second overview:
http://www.youtube.com/watch?v=Ls6X9YIG_t0

First track level video:
http://www.youtube.com/watch?v=_W5EsSJvpXI

Second track level video:
http://www.youtube.com/watch?v=IFyUUCpjYfY

#53

Russ,
Enjoyed the videos.
“Crawl” speed is pretty impressive.
How much run time are you getting using the drill batteries?
Ralph

#54

The total visit was pushing 6 hours but we did not run the engines that long. The SD45 ran the entire time on the drill battery, probably 3 hours. I couldn’t tell if it had lost any power or not, seemed to run just like when it started. I’ve been impressed with how well battery power works.

At the end of the visit Bob ran his steam engine. That was fun. Unfortunately the camera had run out of juice so no video. The train batteries far outlasted the camera battery!

PS, Happy Father’s Day to all!

#55

Moving forward with creating a kit for the RC system. One of the problems I had was making a suitable enclosure for the transmitter. I think I have solved that problem. I bought a very inexpensive CNC machine and set it up to cut the enclosure for the keyboard, LCD and switches. It takes a short time and they look nice. Only thing I should get is a shorter spiral cut bit, the Rotozip bit is a little too long even though I haven’t seen any significant flexing. Here are pictures of the process: Cutting out the front panel:

(http://i68.photobucket.com/albums/i27/rmcintir/Robotics/HPIM3024.jpg)

The finished panel, this is the first one!

(http://i68.photobucket.com/albums/i27/rmcintir/Robotics/HPIM3028.jpg)

Here it is with parts installed:

(http://i68.photobucket.com/albums/i27/rmcintir/Robotics/HPIM3026.jpg)

EDIT (8/1/09): For anyone else making their own enclosures, I found that it is much easier to cut out the front case with the label applied already. Since the spiral bit throws cuttings down it presses the label onto the case and there is no tear out. I’ll have the final pc boards next week to verify they have no errors.

#56

Russ

This appears to be an interesting project.

My question. Does keying the Tx to send a “stop” command, actually produce zero voltage at the Rx motor terminals? Or is a detectable potential still present at the motor terminals?

Thanks.

#57

When a locomotive is told to stop, either by setting its speed to 0 or hitting the all-stop button which sends a broadcast packet to all locomotives, the receiver sets the motor controller off. The PWM input is set to 0 and the H bridge controls are also set off. There is no voltage potential across the motor output.

The all-stop will immediately set all locomotives to 0, it is intended as an emergency stop. Hitting reverse will more gradually reduce the speed of the currently controlled locomotive to 0 before reversing the direction.

Additionally, if a receiver loses signal for over 5 seconds it will shut down the locomotive, i.e. turning off the transmitter.

#58

Russ

Thanks for the response.

Might it be possible in the event of loss of signal, To implement a gradual drop to zero?
Perhaps a time-frame of a second or two.
I’m thinking of catastrophic damage to gearboxes and such.

#59

The all-stop puts the motor controller into a coast mode. Motor coast is different than braking for instantaneous stop. I will try to measure how fast the stops are. The all-stop function is intended as a battery powered equivalent to the shutdown of power on a track powered layout if there is an emergency.

Right now I’ve installed a receiver into a USA Trains F3A/B combo. It is the only locomotive I have with traction tires. I am looking at the effect fast stops have on it. So far the stops are quick but don’t seem to be instantaneous such that gear train damage might occur. I need to determine the affect of a full train consist being suddenly stopped however.

Typically if I wish to bring a locomotive to a stop I hit the reverse button. That automatically reduces speed gradually. Otherwise I just use the throttle.

You reinforced my own thoughts about the traction tires and fast stops with this kind of locomotive. BTW, two seconds is an eternity if you are about to plow the back of a sitting train. As with most things it is a trade-off, fast stop to avoid crash but possibly cause gear train damage.