Murphy's Law #74, "In a circuit where a fast acting fuse protects a delicate transistor, the transistor will always blow thereby protecting the fuse." or in your case, the MOSFET's will toast, in order to stop the breaker tripping . . . .
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Jeff Ferrara
fb@ffej.net

ffej.net

So is there anyway to protect the controllers?
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Tim Team Reaper.

Active current limiting is about the only way to be 90% sure things are going to survive, a fuse or breaker may help protect against dead shorts though.

I wouldnt worry about blowing up the IFI's in a feather under normal use anyway . . . people in the states use them in middleweights without trouble . . .
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Jeff Ferrara
fb@ffej.net

ffej.net

These are the 60 amp ones.
And i will be using 9.6v dewalts at 18 or more volts on large wheels so im not sure if they will hande the motors.
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Tim Team Reaper.

Protecting a combat robot speed controller reliably is hard work..

In combat robotics we are always operating things on the edge of the envelope, with very little safety margin.. so its a fine line between operation and destruction..

If a Robot Speed Controller was designed for an industrial automation application, it would be 4x the size, weight and cost of the present ones we use.. but because we are all weight (and budget in most cases) limited, components have to work with very little breathing space.

To reliably detect this narrow space between "normal" operation, and "overload" is very difficult, especially when you have mere seconds to do so before things start to melt and go boom.

Normally, electronics (current / temperature sensing) is the best way to go, in fast-reactions situations like ours, but that adds a fair bit of cost and complexity to the system.. Jason and I are looking at designing a "Universal Current Limiter" that can be added to an IBC (or any other speed control) to help protect it, but that is still a few months off I'd guess..

The best solution would be to use a bigger controller. If you put a 400 amp controller in where only 200 amps is possible (due to battery limits), then you know you are very unlikely to blow it up. However, as I said, this solution is rarely practical in combat robots.

Fuses are OK for practice, but I wouldnt run one in a battle.. I'd hate to suffer hundreds of dollars worth of damage because a 5c hot fuse popped under impact and left me sitting dead.

I like the look of the Thermal Circuit breakers available from Bursons/Repco.. they're available up to 50amps and are quite small and light.. At least with them if you do have one fire in a match, you're only going to be still for 30 seconds (only!) until it cools off and recloses.

I tried to add a fan to one that only came on when the breaker popped to speed up the breaker reset-cycle, it worked well on the bench, but I forgot that the breaker would be seeing polaritys of both directions and with a widely varying "voltage" (well, PWM mark/space ratio), so the fan didnt like it very much and smoked in the bot. I'll have to rig up a bridge rectifier and a regulator which makes it a bit complicated for a fan-cooled cct breaker.

So Thermal Breakers are the best cheap solution that I know of at the moment.. (if you dont mind being occasionally still if your bot gets overloaded).

They're only a help though.. unless you have the weight, space and $$ to give yourself that safety margin of bigger controllers and/or current limiting, nothing will save you every time when you are running on the edge..
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

I was just wondering if anyone might know where to find
3mm high tensile bolts that are about 60mm long or longer.
Prefer with allen head.
Usually buy bolts from Coventry but at 3 mm thickness they only go up to about 40mm long and I would like them longer.
If they cant be found the second choice would be to find some 3mm rolled threaded rods and cut them down myself but dont know where to find 3mm rolled threaded rod anyway.
Will end up needed about 160 of them.
ANy help appreciated
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Bots that do not destroy you, only make you stronger.

Im thinking of using a 7805t voltage regulator for a bec it ses it can take 35v in and 4.8-5v max out and 1amp supplyed.
How do i wire em up?

Can i reduce interference with a capacitor or something?
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Tim Team Reaper.

bunnings usually have 3mm rolled threaded rod but thats around here not sure bout them mexican bunnings where you are way down south
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as a shadow is seen and not heard i am here
-Waddy the phoenix

i think they have this thing called a data sheet...should tell you something about wiring it up

Catch me on MSN and I'll supply you with a wiring diagram and will even show you what caps to put on it
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https://www.halfdonethings.com/

I went down to dick smith and they done have ANY in stock that will work for what i want so i am thinking of getting a kit that ses it can take 25v so my fully charged 24v pack will be 30v and i have emailed jim at r.m.p and they say the one they have there that ses it can talke 25v has ben run up to 32v successfully so id say this kit can be too as it allso has the caps and stuff on it and can be changed with jumpers to diff voltages so i hope it will work?

Is it a good idea to block up the fan holes to stop crap getting in?
Will the motor over heat?
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Tim Team Reaper.

probabley but if you cool it down after every match ( i had the thought of buying a small air tank to cool down motors after fights) it's should be all right. well that's what i think anyway
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For West ausies interested in robotics email me at: theoneshrug@hotmail.com
OR
dragoonarie@gmail.com
best quote ever:: "Those Gas-Turbine style warehouse heaters arent illegal, and neither is remote controlling one as far as I know."

If i get some spare weight ill put a pc fan on the motors and battery pack to cool them as the one i tested the other day at 24v was soo good that when i accidently stuck my finger in it it smashed off 3 teeth and cut the top of my finger off
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Tim Team Reaper.

How long abouts would a 700mah nicad reciver pack last? or what about a 2300mah nimh pack last?
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Tim Team Reaper.

a good while i would say.

if charged before an event u should have no probs during event
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Andrew Welch, Team Unconventional Robotics