# RC kill Switch



## zephyra (Jan 2, 2008)

After another rebuild of my favorite engine following a spectacular crash when my 232U1 leaped free after the coupling between two coaches broke, I concluded it was time to get serious about a 'kill' switch.

I think I've come up with something simple and easy to install without having to fit full RC. I've fitted a servo in the tender which is connected to the throttle by a thin cord which, in turn, is routed via a small block onthe floor of the engine. The servo is normally fully forward which gives enough slack in the cord to allow the throttle to be operated normally. If the servo is switched, the cord tightens, pulling the throttle closed. I used the 'undercarriage' switch on a Spektrum RC7 to control the servo. I still have to carry the full transmiiter and ideally I'd find a really small single channel system to drive the servo but this is a big step forward! it has the additional benefit that if the tender detachs from the engine - which happens rather too easily on the 232U1 - the cord tightens all by itslef closing the throttle.


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## David_DK (Oct 24, 2008)

232U1 crash! Urgh! - Is it ok? 

If I had a like weise crash I would get serious with the "kill" switch as well. 
Please inform us if it works 

Kind Regards 

David Clement 
DENMARK


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## zephyra (Jan 2, 2008)

232U1 is fine following a re-build with $300 of parts. I just need to paint the scratch on the tender. She came off my track at the very short section where it is 6 feet off the ground







" Sod's law" as they say in my native country!

This locomotive is my absolute favorite - really powerful and capable of pulling 10 heavy J&M Wagon Lit coaches at speed. Just a little too frisky when suddenly freed of load......












Robert


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## weaverc (Jan 2, 2008)

This is why I use a Spectrum 2.4 GHz DX6i transmitter and an AR6000 receiver. When a receiver is bound to the transmitter (a setup process), the throttle is set at 0, or closed. If a signal is lost during a run, the throttle automaticlly closes. A good thing for R/C helicopters and airplanes too. In the case of the AM and FM setups I used to use, the reciever just remembered the last setting when the signal from the transmitter was lost. I like the new technology better.


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## zephyra (Jan 2, 2008)

The point here was not to install a full RC system, but I still prefer manual operation. This installation put a single servo in place with one function - close the throttle in an emergency without interfering with normal manual operation. The emergency might be excess speed or a derailment. 

(I have installed a full Spektrum system in one locomotive and agree that the 2.4Ghz systems are great.....)

Robert


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## David_DK (Oct 24, 2008)

Robert 
First of all. The U1 is in my eyes the best piece of engineering that Aster ever has made. And at the same time the one - without comparison - that looks the best. So I can only congratulate you for being one of the lucky owners. Nice to see it has survived the crash. Anyway I run "old school" as well. So I can absolutely follow you in your viewpoint regarding not installing a full remote system. I presume that some kind of self-contained automatic system is better than a remote. All you need is a speedometer, and a piece of electronics that steps in if speed excess a certain limit. We have here - for fun - build some speedometers, where you use the electronics from a simple bike speedometer, and then use a simple magnet glued on the axel to get a reading. After calibration, its very precise. I have no idea of how you do the last bit, but the benefit wouldt be that it just kicks in at high speeds, and its a small item. 

But I think there is a mechanical version of a top speed limiter wagon in and old number of the NLJ. That might be an alternative. But of course if you loose that wagon you are in trouble again.... 

Regards 
David


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## Chris Scott (Jan 2, 2008)

Add safety chains between coaches/wagons, and between loco and tender? 

Don't you need a deadman's safety switch versus something that has to be operator activated on failure. The latter depends on failure happening a certain way or within your view so you can flip a switch on the transmitter. A deadman's safety switch is independent. There's probably a way to make your single servo a deadman's safety switch.


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## zephyra (Jan 2, 2008)

Duh! Thanks for input and trust me to think of a really complex way to solve a simple problem. It comes from having spent all my career in the computer industry where making simple things complex is sort of what we do!

The really simple solution is a deadman's switch triggered by a speed sensor. The speed sensor could be a small electric motor driven from the trailing truck. Voltage rises with speed and a triggers a op amp when the critical speed is exceeded. Op amp triggers a miniature solenoid that pulls the throttle shut. A mechanical version would be even more elegant.

I'd try it this weekend if it wasn't for the fact that we have guests visiting from the UK and my wife has already given me advance warning of her displeasure if I disappear into my workshop......


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## Chris Scott (Jan 2, 2008)

Posted By zephyra on 09 Jul 2009 03:56 PM 
Duh! Thanks for input and trust me to think of a really complex way to solve a simple problem. It comes from having spent all my career in the computer industry where making simple things complex is sort of what we do!

The really simple solution is a deadman's switch triggered by a speed sensor. The speed sensor could be a small electric motor driven from the trailing truck. Voltage rises with speed and a triggers a op amp when the critical speed is exceeded. Op amp triggers a miniature solenoid that pulls the throttle shut. A mechanical version would be even more elegant.

I'd try it this weekend if it wasn't for the fact that we have guests visiting from the UK and my wife has already given me advance warning of her displeasure if I disappear into my workshop......

Call this thinking out loud - which I thinks means I have plausible deniability ... Thankfully.












Wouldn't a Deadman's Safety be controlled by a single trigger event to shut whatever it is down. Like the foot peddle on a locomotive? 


"...a Deadman's switch triggered by a speed sensor. The speed sensor could be a small electric motor driven from the trailing truck. Voltage rises with speed and a triggers a op amp when the critical speed is exceeded. Op amp triggers a miniature solenoid that pulls the throttle shut." This seems like too many varibles (or vunerabilities). 


Consider:
The throttle should be configured in a "normally off" position. Running the locomotive requires opening the throttle which is under the spring's tension to return to its closed position. A single event then triggers shutdown; the throttle automatically and immediately retuning to the normally off or closed position.


Consider:
A spring on the throttle shaft, with just enough tension to keep the throttle closed and return to closed if opened (rotated open). When released by a single triggering event the throttle can return the throttle to its normally closed position.


The Spektrum 2.4GHz product(s) have telemetry capability, one of which is speed detection through RPM. This is meant to detect an RC car's wheel rotation. In the case of a locomotive a sensor on one of the drivers or another locomotive wheel. If speed is The critical factor/event, as mentioned, then use of the RPM sensor to trigger the release of the throttle would seem to be an effective Deadman's Safety solution based on a single event; RPMs.


Whether the Spektrum transmitter and telemetry unit is capable of sync'ing a telemetry event to transmitting a servo command I do not know, but I think it is worth investigating. Possibly another 2.4GHz mfg's product has the capability of linking telemtry data to a channel servo command.


If the Spektrum unit does not support such a immediate direct channel response servo command there seem to be two options: 


1. Worst case, if no 2.4GHz product that supports telemetry that can trigger a channel command to a servo, the telemetry signal will be read/detected by the transmitter operator who can, via a transmitter servo switch, release the throttle servo allowing the throttle spring to return the throttle to its closed position.


2. This is a variation on #1) Spektrum has a failsafe capability. If there is a failure, loss of communication to the receiver, i.e., power failure, etc., any servo returns to it's user programmed default position. The failsafe setting for the throttle servo is with the throttle closed. The operator shutting down the transmitter would cause this failsafe response, the servo returns to it's throttle normally off position.




Last resort... You could also have a small explosive device that when triggered blow apart the servo-throttle connecting rod and the throttle shaft spring causes the throttle to close.












Like I opened with, just thinking out loud ... Others can make their own judgment whether I should have simply kept my thoughts to myself.


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## zephyra (Jan 2, 2008)

Chris, you must also work in the software industry









I went through much the same thought process and even purchased the Spektrum telemetry unit to try this out. I haven't yet found a way of using telemetry to trigger a servo event although it is cool to get a continuous read-out of the scale speed.


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## Semper Vaporo (Jan 2, 2008)

Not sure if this would work with the present "Modern" digital systems, but there is a device that is put between the Receiver and Servo on the older type R/C systems that causes the Servo to move to a predetermined position if the RF signal is lost (or if the DC power drops too low). The Device plugs into the Receiver where the Servo normally does and the Servo is plugged into the Device.

You turn the Receiver On with the Transmitter Off and adjust a pot (on the Device) to move the Servo to where you want it to be if there is no RF signal, then when the Transmitter is turned On the Receiver and Servo work as normal. If the Receiver loses the signal the Servo returns to the position that was set. In Airplane R/C systems this usually set the rudder and ailerons to a gentle turn to try to return the plane to be nearer the Transmitter (assuming that is why he RF signal was lost). 

I used to use one of these Devices in my Live Steam R/C setup to put the Reverser Lever in neutral. (I tried setting the throttle to a closed position but found the servo was not quite strong enough to force the throttle to the FULL closed position against steam pressure and the engine would continue to run slowly). Unfortunately, the Device I had was way too sensitive to the Receiver's battery voltage and my run time was severely shortened over what I could get without the unit... 1/2 hour vs. 2+ hours! So I took it out.

If the Transmitter were equipped with a spring loaded normally open switch that must be held in the closed position by the user's hand, then if the Transmitter were dropped (dead operator?) then the Transmitter would be shut off and the loss of RF signal at the Receiver would cause the train to stop.


But, I thought the Original Question here was how to shut down a train if it separates, not a "Deadman's switch" in the hands of the operator. I suppose the Receiver antenna could be attached with an easily separated connector. With the Receiver in the engine and the antenna in the first car after it, if they separated the antenna would disconnect and maybe that would be enough to cause a complete enough loss of signal to activate the device as I explained above.

??


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## Chris Scott (Jan 2, 2008)

Posted By zephyra on 10 Jul 2009 05:25 PM 
Chris, you must also work in the software industry









I went through much the same thought process and even purchased the Spektrum telemetry unit to try this out. I haven't yet found a way of using telemetry to trigger a servo event although it is cool to get a continuous read-out of the scale speed. 

Nope, hardware type. Software geeks were/are always too tempermental.


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## Semper Vaporo (Jan 2, 2008)

Posted By Chris Scott on 10 Jul 2009 08:54 PM 
Posted By zephyra on 10 Jul 2009 05:25 PM 
Chris, you must also work in the software industry









I went through much the same thought process and even purchased the Spektrum telemetry unit to try this out. I haven't yet found a way of using telemetry to trigger a servo event although it is cool to get a continuous read-out of the scale speed. 

Nope, hardware type. Software geeks were/are always too tempermental.






















Tempermental????









Tempermental!!!!!









TEMPERMENTAL?!?!?!?!!

WHO YOU A CALLIN' TEMPERMENTAL?









TEMPER-MENTAL! HA! So much for you "HARDly-aWARE" types!

Sheesh!









You just see if we ol' SOFTyWARE types write "work-a-rounds" for your weak hardware failings anymore!









(Tempermental! HA! Bah, Humbug!)


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## Chris Scott (Jan 2, 2008)

Posted By Semper Vaporo on 10 Jul 2009 09:37 PM 
Posted By Chris Scott on 10 Jul 2009 08:54 PM 
Posted By zephyra on 10 Jul 2009 05:25 PM 
Chris, you must also work in the software industry









I went through much the same thought process and even purchased the Spektrum telemetry unit to try this out. I haven't yet found a way of using telemetry to trigger a servo event although it is cool to get a continuous read-out of the scale speed. 

Nope, hardware type. Software geeks were/are always too tempermental.






















Tempermental????









Tempermental!!!!!









TEMPERMENTAL?!?!?!?!!

WHO YOU A CALLIN' TEMPERMENTAL?









TEMPER-MENTAL! HA! So much for you "HARDly-aWARE" types!

Sheesh!









You just see if we ol' SOFTyWARE types write "work-a-rounds" for your weak hardware failings anymore!









(Tempermental! HA! Bah, Humbug!)


Software Schedule: The software will be finished in two weeks.


Free beer tomorrow.


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## Semper Vaporo (Jan 2, 2008)

Well, at least it'll be done before the hardware is ready.


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