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FAIL SAFES!


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timmeh
Experienced Roboteer


Joined: 20 Jul 2004
Posts: 2517
Location: Victoria


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FAIL SAFES!

Heres a handy little failsafe unit i found on the team knightmare site and allso a little battery ilimenator Circuit

http://www.robotcombat.com/marketplace_rc.html under R\C ACCESSORIES

And i was thinking about useing a high current switch with a servo to turn it on to controll my spinner motor will this comply with the robowars rules if i make it so the zero point that it reterns to when there no signal is made so it will be in the off position and eaven if it twitters a bit the switch is pretty stif and the servo will have to be all the way to the left to turn on the switch its just cheaper then buying a big seloniod and a RSGEX Dual Switch Module.

If not i will just buy one of the failsafe units on robotcombat.com
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Post Mon Aug 02, 2004 9:28 pm 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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If you can get your controls to switch off when the radio signal is lost, then that is a valid failsafe.

To elaborate, if we ask you to turn your weapon or drives on, then switch your transmitter power off with the weapon or drive channel still in the activated position, your failsafe needs to recognise loss of signal and return all weapon and drive channels to the off state.

I dont see how you are going to do that using a servo without a failsafe module or PCM Radio (with built in failsafes) though. When the signal is lost for an "AM" or "FM" radio, the servos usually either stay where they were or jitter about randomly. if the servo was in the on position when that happens, it will quite likely stay on.

But if you have an idea that can demonstratably and reliably pass the power-off-while-active test, then feel free to use it, and let us know how you did it ! l: Smile
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Post Mon Aug 02, 2004 10:10 pm 
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Grotto



Joined: 30 Aug 2005
Posts: 38
Location: Morisset NSW


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Power-Off-While-Active test query

With the POWA test, is there a timing issue in there?
As in the device "must power down within X seconds",
or anything like that?

Also, does this test encompass BOTH weapons and movement,
or are they separate tests? (as in movement being on a different level
of failsafe to weapons)
My chalkboard design is killing both movement and weapons if RC is
turned off/signal lost FOR 5 WHOLE SECONDS... Exclamation
Is this a problem I need to fix? (Easy to do, simply a Picaxe
programming issue)

Sorry if this is in the rules but I cant find where I put them atm
and this subject is already open... Embarassed
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Post Mon Nov 07, 2005 1:20 am 
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Totaly_Recycled
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Joined: 15 Jun 2004
Posts: 1346


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Brett can fill you in more on the failsafe times ... i think most controlers fail safe if signal is lost for around 2 mili seconds ..in my opinion this is too smal a time delay ..But 5 seconds would be way too much ..a wheapon that could spin up in 2 or 3 seconds if activated would be lethal if it hapened in the pits ..my opinoin is set the fail safes for half to one second and try it Like brett said you mainly have to show that when your bot is going flat out and you turn your transmiter off that the drives and wheapons shut down .Also the bot should be able to be powerd up with the radio off and not take off acros the floor because a servo switch or something is turned on and cant center with out radio signal present .

Post Mon Nov 07, 2005 9:05 am 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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Failsafe sensitivity timing should be obvious to the builder as to whats required to be safe rather than a printed pre-determined number.

In the event of a robot that can cover 10m in a second from a standing start with a saw that spins up in .5sec, then obviously a 1second failsafe would be far too long. a slow wedge might get away with 3 seconds without seriously endangering life and limb.

a pneumatic bot's failsafe would want to be tuned on the "are you absolutely sure you want me to fire this ? tell me 5 times in a row with no errors to make sure" type of thing.

Ideally, I'd like to see something like a sub-1 second shutdowns on drive and weapons on a radio-signal loss, and a sufficiently slow (2 seconds on continuous valid stable signal) before powering up again, but this may be varied at the discretion of the safety inspectors according to *their* perception of the relative danger level of your bot.

Think of it as sending your bot to obedience school.. We're going to be looking a lot harder at any Rotweilers or Doberman Pinschers Wink that dont "sit and stay" when told to than we are any Chihuahua's.. Its common sense.
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Post Wed Nov 09, 2005 1:21 pm 
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Grotto



Joined: 30 Aug 2005
Posts: 38
Location: Morisset NSW


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Cut off times

Hmmm. That makes it tricky, relying on diffferent
peoples "opinion" on the night as such.

But it IS a safety issue so I can see why its done that
way now.

So I'll look at a 1 sec delay on my drive train as I
expect it to be pretty sluggish on takeoff and
0.5 secs on the weapons systems. And both take
5 secs to recover after cold boot or signal loss.

Youve gotta remember I'm still designing the nervous
system of my first battle bot.
Surprised He dont have no body! Surprised

Thanks again
Grotto
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"The future is not set. There is no fate but what WE make."
........CEO Cyberdyne Systems

Post Fri Nov 11, 2005 6:28 am 
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Valen
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Joined: 07 Jul 2004
Posts: 4433
Location: Sydney


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radio reception in the arena typically sucks.
you want it to turn on again as fast as possible
(assuming you have valid signal)
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Post Sat Nov 19, 2005 2:02 pm 
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