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Ajax
Experienced Roboteer
Joined: 17 Jun 2004
Posts: 298
Location: Sydney
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DumHed,
What you have just explained about your radio control configuration
quote:
My receiver does shut down the servos if there's no input signal, but obviously it won't turn off the main power if the power switches are jammed in the on position and there's no radio.
That is against the safety rules!!
This is a dangerous sport so I would recommend that you re-address your control design.
A suggestion that I can make is to install a main relay circuit, to cut all power from the batteries, if there is no transmitter signal.
This is where the IBC has its advantage. If anything goes wrong power is cut. Yes it is over $300, which just means you need to put some extra armour around it. Or put something else in that is safe.
If I were a technical inspector at an event I would not allow your bot to compete for safety reasons. Sorry, not trying to be nasty. But everything needs to be safe, for other competitors, spectators, and to comply with Insurance companies polices _________________ It's all about the destruction.
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Wed Jul 07, 2004 12:54 am |
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DumHed
Experienced Roboteer
Joined: 29 Jun 2004
Posts: 1219
Location: Sydney
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those look ok, but realistically there are always going to be times when a failsafe is not fail safe.
If your receiver power is cut (as it was in mine) then that particular unit will be of no use at all, since it still needs power to return the servos to the brake point.
If power is gone it won't do anything, and if a servo or servo horn is damaged you can still end up with weapon power being on even if the receiver and fail safe are working.
The only way I can see it working properly is to monitor the receiver outputs, and hold a relay energised as long as the servo pulses are all within spec.
That way if you do end up with major mechanical damage the relay will either drop out due to lack of power, or you can turn off the transmitter to cut power completely.
Of course you can still end up with power being maintained if the relay welds itself on (easy to happen with stalled high current motors), or wiring get shorted out.
This can happen even with an IBC or similar. If you cook the FETs and they go short, or you cop a hit that shorts the motor power on you won't have any way to stop it.
Personally my view is that with 12kg bots the fail safe is not that important, since it isn't possible to cater for all conditions anyway, and the power available isn't that great - so there's not really a huge danger present.
I'd be inclined to stick with the cutoff switch / removable link on the main power - and then focus more on having a way to disable errant bots physically.
If a bot is running around the arena flat out with the weapon running the best way to stop it would be to throw a large blanket over it, and to have a bit of 4x2" timber or something to push it around if necessary.
Really it's a bit stupid to rely on an electronic failsafe when it can only prevent problems caused by a complete loss of transmitter signal.
Next time I'll have my own multi channel electronic controller anyway, which will pass the usual requirements - and will cost a similar amount to one of those fail safe units. _________________
The Engine Whisperer
- fixer of things
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Wed Jul 07, 2004 12:08 pm |
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