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Julian we have a remote kill for the petrol engine in Typhoon 2. This was used twice in series 7 when we hit the arena sidewall. The only other kill switch is the failsafe which when Tx contact is lost the robot stops dead. I guess you could in a way call it a remote kill switch.
Weve recently had a similar discussion in the Netherlands. The problem is that FETs can stay in a conductive state if they let out the magic smoke, and relays may stick. Allbrights are the best option, but they are not cheap and carry some weight. This has put a lot of people off.
Im all for a remote relay option. I even suggested to put an infra-red sensor on it so you can shut it down from a distance if the receiver fails somehow. The problem is it will make the sport even more expencive and it reduces relyability a bit because it is yet another component that may fail.
Apologies Pneumatic people - my mistake.
Ill stick to talking about things I know about !
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Eds solution is quite a nice one- disabling the drivers is effectivelly having a fail-safe on a switch. Is this the sort of thing the rule is after, or is it more of a kill switch in the strongest sense of the word- i.e. removing power to the bot?
Paul Cooper said:
M2 has always had remote kill and simply uses a pair of cheap (£15) 180A relays feeding the speedo channels.
How do you turn these relays on or off paul. I know its via a switch on the TX but what does this switch activate?
All help would be greatly appreciated.
Regards
Ian
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.
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.
Oh ok but that wont really work if you have your rx run from your main batteries will it?
Regards
Ian
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
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 :)