Hmm i may go ahead and buy one since aaron may have a solution to the failsafe problem and im sure later on there will be others.

If say there was a new program upgrade for the reciever you would have to buy a new reciever to get it wouldent you as the reciever wouldent be set up so you can update it would it?
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Tim Team Reaper.

Just wait till I run the idea past Brett I might have missed something simple..

I've got the PCB worked out..

It should kill 4 RX channels, and all you have to do is plug the throttle into the throttle channel, and the other 4 into the RX where you need them. Then plug you ESC's into the 3-pin headers mounted on the board and off you go. It should work safely with any BEC units and there is even a spot to connect your own RX pack onto it if you want. All within 30mm x 40mm x 10mm.. Let's just hope I haven't forgotten something stupid in the process of rushing this solution

I'll do the wiring diagram up for Brett tomorrow after I get home from work, because I know he loves my PCB-before-schematic designs
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https://www.halfdonethings.com/

Heh, I was just about to growl at you for that. Posting a PCB layout instead of a schematic reminds me of pirate treasure-map style directions. take 6paces left from the coconut tree..
(crawl stagger crawl crawl.. no hang, was it stagger crawl stagger stagger ? )

Any method you want use to implement a failsafe is fine by me, as long as it can be demonstrated on demmand that the bots drive and weapons power down promptly and reliably when the radio link is lost.

The PicAxe idea is fine as far as the rules are concerned. Practically it adds complexity and more "failure points" (things that can go wrong) to the system.. a lot more servo leads to break, fall off, plug in backwards, , micros crash and so on..

It would be nicer to see the failsafe function in the radio work natively, but theres nothing in the rules against an add-on failsafe, as long as it works..
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

quote:

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Originally posted by TDT:
Actually... I just had an idea.

If i built a board with a picaxe 18X that watched the throttle channel, if the throttle channel drops below 20% (indicating a failsafe), the picaxe turns a transistor off, which cuts the signal wire between the ESC and radio. So all the other channels would lose the signal from the RX and they would failsafe.. I believe this would cost around $20 to make and will handle 6ch easily...

I'll get to work on a circuit diagram for those interested....

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Hence the battery pack to keep power to the board so the reciever stays on incase you acidently disable the esc and you can just turn it back on again.

The throttle has no spring so it will stay were ever you leave it.
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Tim Team Reaper.

personally I think the whole failsafe thing is a bit dumb.

The only thing it protects against is loss of radio signal.

Relays can weld on, MOSFETs can go short, wires can melt and stick together, contacts can be jammed by physical damage, servo arms can snap, etc, etc, etc - even with perfect radio signals.

A total loss of signal or interference bad enough to drive the robot around by itself is very rare (I don't think I've ever seen it happen) but all the other mechanical and electrical failures are quite common.

If the bots are only powered up by their owners, and in the arena then it's all pretty safe.
If a radio problem causes the bot to go running around the arena with its weapon on then all we need to do it wait for it to run out of power or stop by itself.
There's obviously the slight worry of robots firing up by themselves any time the main power is on, but anyone who doesn't assume they can, even with a failsafe, is an idiot.
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The Engine Whisperer - fixer of things

quote:

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Originally posted by DumHed:
There's obviously the slight worry of robots firing up by themselves any time the main power is on, but anyone who doesn't assume they can, even with a failsafe, is an idiot.

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quote:

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Originally posted by CELL DAMAGE!:
Hence the battery pack to keep power to the board so the reciever stays on incase you acidently disable the esc and you can just turn it back on again.

The throttle has no spring so it will stay were ever you leave it.

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Arron,

You've shorted outputs 4 - 7 togeather. you should only need to use 1 output to switch the transistors on or off.

quote:

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You've shorted outputs 4 - 7 togeather. you should only need to use 1 output to switch the transistors on or off.

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you mean mA, not mAh
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The Engine Whisperer - fixer of things

The failsafe issues *is* only a limited form of protection. All builders know that. There are indeed a lot of other failure points that can send a robot out of control with the radio link working perfectly. Relays, Mosfets etc..

However, Radio Control issues are the most common (as we all know) and are fairly easily guarded against. Coming up with a system to remotely disable a stuck-on weapon relay isnt so easy. So tackling the major one first makes sense. As bots get more dangerous in the future, so too will the remote-disarm requirements very likely increase.

Pointing out that failsafes arent really needed when the bot is actually in the arena has been said before. The fact is bots are *often* powered up outside the arena, frequently in places they really shouldnt be, for testing, demonstrations or whatever, and it is *then* that the failsafe becomes a worthy layer of protection for those present.

And lastly, as I mentioned before, part of the reason for failsafes are as a reassurance to the average member of the public that we do "have a leash" on these things, and that they are well-trained and wont do anything without instructions. That may not be a 100% guarantee, but I personally would feel more comfortable around a big dog that had been to (and passed) obedience school, more than a dog that hadnt, even although that is not a 100% guarrantee either.

If nothing else, it shows that the owner has at least put *some* consideration towards making sure his device is obedient.
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

mA is a measurement of current flow per second. when the time unit is unspecified, it is presumed to be one second.

mAh or mA/Hr is current flow per hour. mainly used as a measurement of battery capacity, it supposedly specifies the number of milliamps (or Amps) the battery can supply for one hour.

In actual fact, this rating is usually specified at a *20 hour* discharge rate test without actually stating so. Limitations in battery chemistry make it unlikely that the battery can actually supply the A/Hr (or mAh) current for one hour. - a 7A/hr battery should be able to supply .35amps for 20 hours, but it probably wont supply 7 amps for one hour, so this rating is often misleading.

So, what Dumhed meant (I think) is that its the "hour" part of the "mAh" value you used that is incorrect, not the case of the A. the current value in circuits is always specified at the 1 second rate.
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

yeah the case of the A doesn't really matter, but upper case is the standard symbol for Amps. Lower case m is for milli, with upper case M for Mega.

On the failsafes, I really don't think I can remember any instance of a bad signal related issue.

There have been plenty of stuck switches, relays, melted wires, and speed controllers while in the arena (which is not really a problem), but everything that's happened outside the arena has been user error. (Welchy's incidents, Scoopy chopping the desk in the pits at Robowars II, and the occasional drive power up while on the bench.)

I think some sort of system to make sure control stays off without a valid signal is good, but it's not impossible to have intererence that looks like a valid signal, especially when there are heaps of other radio control systems around.
If someone powered up a transmitter on the same frequency (even from outside the event), a control failsafe won't do anything to help.

I just don't like the idea of anyone relaxing their concerns due to a blind faith in a "failsafe" of any kind.

My bot hasn't had a single instance of intererfence causing drive or weapon activation, but I make sure the power is disconnected unless it's in the arena or is set up safely for testing.
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The Engine Whisperer - fixer of things

The mostly likely reason you cant think of a dangeruous signal-related issue is *because* the robots are all equipped with fail-safes..

I'm sure you will remember plenty of circumstances under which a competitors bot has refused to respond to a noisy radio signal and has sat there and twitched or done nothing. Without a failsafe, 50% of these would have been "refused to stop doing something".

I agree that having a failsafe should not make one complacent.. No piece of circuitry is an acceptable substitute for a cautious intelligent operator, but they still fit seatbelts to cars. Even intelligent operators suffer from brain-fade on occasion..
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people