Rule 4.4 Remote Kill (Advisory Only)

[Guest]

Rule 4.4 Remote Kill (Advisory Only)

My IBC has an output for an external relayed channel on it, when I get chance to play with the finer points of the bot, Im intending to connect a DPDT relay across this and route the drive motor leads via the relay. My spinner is controlled by an Electronize, the power supply for which is fed through a separate relay channel. Well, it will be if I can ever get the damn electronize to stay in neutral.

[fwsorg]

Rule 4.4 Remote Kill (Advisory Only)

Ian- you canget solid state switches for Rxs from loads of places (technobots is prob the best place). They are just a circuit which plugs into the RX and switched either on or off depending on how you move the stick. Simple.

[team_ireland]

Rule 4.4 Remote Kill (Advisory Only)

Oh ok but that wont really work if you have your rx run from your main batteries will it?

Regards
Ian

[team_ireland]

Rule 4.4 Remote Kill (Advisory Only)

Found something that might help people. I am currently trying to work it out for myself. Thanks Garath

The Link:
http://www.lancasterbombers.com/electronics.htmhttp://www.lancasterbombers.com/electronics.htm


Regards
Ian Mc Donald

[fwsorg]

Rule 4.4 Remote Kill (Advisory Only)

With regard to turning the FET drivers off being insufficient, I would say it is sufficient as the rule says it should bring the robot to a failsafe position, which one would interpret as meaning it failsafes. Certianly all the PIC based speedos ive seen failsafe by turning the disable pin high on the drivers. Whilst i cant speak for Eds I would imagine it does the same thing. Further to that, with the arguement that MOSFETs have been known to remain conductive having smoked, its normally only one FET that smokes at a time, and assuming were refering to h-bridges, the current has to pass through 2 fets, so the remaining fet should work anyway and stop the current flow.

Conclusion? Turning off the fet drives is a good solution in that its only a couple of extra lines of code, so it weighs and costs nothing extra, unlike switched and relays. On the flip side, only programmer types are in a position to do this anyway, so for the rest of us its switches and relays

[m2xt]

Rule 4.4 Remote Kill (Advisory Only)

Eddy, I have seen a number of bots out of control due to a) speedo failing with a shorted FET driver (quite common on NCC70s) and b) due to a CPU crash - if you say watchdog in reply then think again! In both of these cases attempting to turn off the driver enable will have no effect. I still believe that a remote kill that switches off the FETs is fine in most cases but is not as good as a electro-mechanical power interrupt but far better than nothing. I will never run a heavy without a power relay circuit, if nothing else, it has saved the embarressment of a runaway bot following a Vantec crash.

Paul

[fwsorg]

Rule 4.4 Remote Kill (Advisory Only)

Thank you Paul. That would suggest that the rule may need perhaps some re-wording, as it is not too difficult to take a seperate channel of the TX/RX which should bring the robots failsafe devices to the pre-set off or zero position via a switch on the TX. as meaning that making the controllers failsafe as they normally would is acceptable. As you have described above, that seems to frequently be insufficient. Perhaps in the next revision of the rules (whenever that may be- I seem to remeber Andy Kane mentioning that due to insurance they are either fixed now, or soon to be fixed, for a set period) a note be added on what is deemed acceptable- i.e. that relying on a uProcessor of FET driver is not really suffiecient, or at least not the prefered method? I have no problem with conforming to either of these, but will from now one favour the relay approach.

Thanks,

Eddy

[jim]

Rule 4.4 Remote Kill (Advisory Only)

Good to know Im in the clear about the CO2 tanks. No need to apologise, Ed - if you have concerns you have to raise them even if you dont know everything about the field in question (who does?)

Whatever remote kill system you put in place can of course fail but if you make your weapon or drive reliant on more than one system (speed controller plus relay for example) and you keep them as separate as possible you drastically reduce the risk of a runaway robot.

I will see if Maplin have any of the 180A relays tomorrow for my robots. I suspect that space rather than weight will be a problem for many existing robots though.

[fluppet]

Rule 4.4 Remote Kill (Advisory Only)

This is where my not-yet-roboteer paranoia comes in. Id been wondering about failsafes (for heavyweights). Although I wouldnt want the failsafe to fire when not needed, Id want the fail safe to be *really* safe.

The old Phoenix mainframe in Cambridge used to have a shutdown which fired a glass bolt through the power line (we hypothesised it was for use if it ever became self-aware). Id kind of been thinking along those lines for the robot - chomp a (replaceable) wire as it leaves a battery terminal with a spring-loaded nonconductive (ceramic?) blade of some kind, with a small solenoid holding it in place. Strikes me as a simple and pretty reliable system, and probably not too heavy.

I like the infra-red backup idea, by the way.

Would I be vastly over-engineering this?

--
Fluppet

[bugs]

Rule 4.4 Remote Kill (Advisory Only)

Euhm...
YES!

[fluppet]

Rule 4.4 Remote Kill (Advisory Only)

Just so long as I know. :-)

--
Fluppet

[team_ireland]

Rule 4.4 Remote Kill (Advisory Only)

Well Andrew basically all you need is just to be able to turn on and off the power to the drive and weapons. This can simply be done through some large relays (about 70amps per motor for feathers and 150amps per motor for heavys) These could be simply turned on and off by an electronic relay device such as the electrolise range from technobots.


On a different note would Ian Watts Failsafe double as a remote kill switch?

Regards
Ian

[fluppet]

Rule 4.4 Remote Kill (Advisory Only)

Okay; Im just particularly allergic to pain when it comes to being attacked by 100kg robots. :-)

If someones wandering around with random radio signals (as at the Robot Rumble 2003 when some kids were playing with an r/c car outside) or if theres a chance my electronics might go haywire - always a possibility, if someones stuck an axe through them, or if theyre designed by someone as incompetent as me - I like the idea of being able to kill the thing. Being able to do it in such a manner that it cant get switched back on again would be favourite.

Of course it does mean Ill have to make damn sure that nothing activates it when I dont want it to, but thats a small price to pay. Im made nervous enough by the idea of sticking my arm through some railings to stick the link in - trapped limbs and snapping noises haunt my thoughts, and in the past Ive proposed the idea of a cattle crush to hold robots still before entering the arena. Trying to turn off a robot which is going King B or doing a Behemoth (vs Mute) isnt my idea of fun, if the control system is already known to be flakey. I have an innate concern that relays might weld themselves in nutty robot mode, and for as long as I might consider things like flippers which automatically fire when somethings on them, I want to be sure my failsafe wont get stuck.

I trust (relatively) everyone else to be competent with their failsafes - but since Ill be the one with my hands on the removable link, I reserve the right to be very paranoid with my own! (Its just nice to know *how* paranoid!)

Anyhoo, back to people with less extreme solid-state systems (which Ill probably use as well - no need to spend more time than necessary replacing wires!)

--
Fluppet

[wenman]

Rule 4.4 Remote Kill (Advisory Only)

Ian as Paul says it is quite possible for speedos to fail in a state where they just run even without a signal. In this case the failsafes will not stop a run away bot.

I actually had this happen on my weapons speed controller once, luckily it wasnt connected to my disk at the time. Thats why Im intending to use a mechanical relay this year.

Im using the Ian Watts interface as well this has two weapons channels & I intend to use one to control a mechanical contactor. Now of course someones going to argue that I shouldnt use the mixer to control the contactor in case my mixer fails .

Richard Wenman
Team Mayhem

[team_ireland]

Rule 4.4 Remote Kill (Advisory Only)

Its sounds to me Andrew that your a little too paranoid. If your that paranoid about getting hurt or something going wrong then robotic combat may not be the sport for you. Perhaps tidley winks is more suitable

But the most safety concious teams i.e. Big Brother, Tornado, Shredder and Dantomkia all have something simular to relays fitted. Now by saying there the most safety concious I am not taking away from anyone else I am sure that most if not all teams are very very very safety concious but those 4 sprang to mind.

As for relays welding themselves shut jsut make sure the current your robot can draw is much lower than the relays mak current i.e. if the robot can draw 10 amps use a 15-20amp relay. Equally if the robot can draw 200amps use a 300-400amp relay. Thats my opinion but as I said its up to you.

Regards
Ian