well yeah sorta but having a failsafe on weopon is most important if its a dangerous weopon.

Depends on event and runner of event if its really crutial but i see your point.
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Andrew Welch, Team Unconventional Robotics

As i recall brett said as long as your bot dosent move in testing when the controlle is off thats ok with him.

Id say that only applies to the drive not having a failsafe.
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Tim Team Reaper.

Ajax is correct.. Active weapons require a failsafe *as well as* the drive system.

when I say "doesnt move", that means *any* part of the bot, spinning weapons, lifters, flippers etc.

The failsafe test will be something like activating the drive (and weapons if safe to do so), and turning off the radio while its running.. *ALL* motion must stop.. weapons included.
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can you hook a single failsafe to the reciever, or do you need one for each channel?
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YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH

If you are using servo motors on a non-PCM receiver, then you need 1 failsafe per receiver channel that you want to auto return to off.

So if you are using Microswitches in the usual H-Bridge configuration, you will need 2. If your switches are setup in the drive/steer configuration (not a great idea, since you cant turn on the spot), then only the drive one needs a failsafe.

If you have an active weapon being switched on and off, then you would need an extra one for that too. If you need all 3 of them, it would almost be worth spending the extra money and either building a simple pic-axe relay controller, or going for something like Electronize's or an IBC, since you'd be looking at over $100 worth of failsafes.
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well when i pull out drill trigger controllers i will look into ways to have a springs or something to push servo back to centre or until stuff turns off as it would save money.

for weopon it would be pretty simple to make up something to failsafe but for drive it would get trickyier.
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Andrew Welch, Team Unconventional Robotics

Do you not failsafe the main battery supply?
It negates the need for multiple failsafe devices.

please xplain in more detail and/or how i could do it. thanks
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Andrew Welch, Team Unconventional Robotics

What exactly do these failsafes do? Do they auto return the servos when there is no signal? Because in this case the only thing they protect against is if you lose signal, if there is reciever battery problems they do not help at all.

Personally atm i am building spring return systems for my servo switching and once they are done I will let everyone know how they go and how I built them.

Failsafing the main power would also work, but from what I understand the normal failsafes would take a bit of modifcation to do this. This system would work better than normal failsafes as far as I can see, because you would set it up so the robot has to be recieving the transmitter signal to turn on the main power. This would also mean switching off your controller would deactivate the robot, giving you complete remote shutdown. This system should only need one failsafe, any problems or downsides anyone can see?

It depends on the failsafe..

Most speed controllers have one built into their microprocessor that simply monitors the servo-drive pulse for out-of-spec invalid servo signals. If they receive an invalid servo pulse, they shut the motor drive and auxillary ouputs down until they have received a number of valid pulses in a row, when they start up again.

PCM Radio receivers monitor the receiver voltage as well as the digital error-checked signal from the transmitter and if either go out of spec, then they set the servo ouputs to a pre-set position, or hold the last position as programmed.

Add-on Failsafes usually check the incoming servo signal and if it goes invalid, then they set the output to a preset position (usually adjusted with a trimpot screw on the failsafe). I dont know if the aftermarket ones monitor receiver voltage as well.. they could do, since the servo power and receiver power are the same voltage.

Spring return systems are fine, as long as they reliably shut things down when you turn off the radio.

Failsafing the main power might work, although it would require a big high-current servo-actuated main power switch, and obviously couldnt include the receiver power, or once you switched off, you would stay off until manually reset, which might be annoying in a match

You would need a spring return on your main power actuater servo as welll.

Apart from the safety issues, one of the main uses of Failsafes is reassuring Insurance Companies, Venue Owners, and Legal Beagles that these destructive machines are completely under our control (hah)..

"Yessir, All I have to do is flip this radio off, and that there machine wont do a thing"..
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lol what is this control you speak of

well ive had 3 runaways with the IBC because of the aerial dangling down and touching the metal frame, twice it planted itself into my side wall and another it took a mad dash for freedom up the road (it was on 24v at that time so it was FAST).

spring returns would work but they would really make the system slow as all hell, unless you have the micros really close to the servo horn.
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Failsafing your servo's or esc's isn't foolproof ..... microswitches can become shorted out i.e. welded in the on position ....likewise esc's can do much the same thing.

A failsafe opearated relay / solenoid ( rated to take your robots current ) in the main battery line negates this.

This relay can be operated via a R/C switch ..... either an off the shelf item like the RCE 200 or the microswitch servo method......( A weapons channel would be ideal as this will usually have one of it's functions spare).

An added benefit of the above is the ability 2 turn off ALL the Robot remotely.


http://www.robotcombat.com/store_td-rc.html

Last edited by Woody on Thu Dec 02, 2004 5:09 am; edited 1 time in total

quote:

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ive had 3 runaways with the IBC because of the aerial dangling down and touching the metal frame, twice it planted itself into my side wall and another it took a mad dash for freedom up the road

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Receivers can continue giving valid but erratic pulses with the transmitter turned off.

A decent failsafe recognises that these are only random pulses of a valid command signal.

The technique that most ESC failsafes I have seen/read about use is simply an "x" valid pulses in a row before activation, 1 invalid to deactivate.

so if you receive a jittery signal with a single-invalid pulse they failsafe, anbd then require say 7 valid signals in a row to reactivate.. not good for control at marginal signal levels, but nice and safe..

it still wont stop a receiver that suddenly "drifts" from valid to invalid over a period of a second or so as I have seen some do though.
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