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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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Thats true, but Al, make sure you understand that to be legal to compete at any public-event (or anything other than a back-yard competition), some form of "failsafe" is required - A system that shuts down the robots weapon and drives when the radio link is lost.
Standalone Servo-driven switches will not failsafe and so are not allowed at RoboWars - the other (private) events usually do allow them at the moment, but this will probably change as those events grow.
You can make servo-switches legal with the addition of a small hobby failsafe-unit for about $30-$40 per channel, but by the time you get up to 3 channels (2 drive, 1 weapon), and have to add $100+ worth of failsafes suddenly they dont look so cheap any more.
I have heard that the modified drill-trigger method will shut-down when the radio fails, but havent seen this for sure yet, but that might be an option.
Depending on how tight the budget is, the easiest and most reliable method is always to just buy an electronic speed controller with failsafe, mixing, weapon control and so on built in, which is why 90% of teams go that way, but there are cheaper alternatives if you dont mind fiddling about a bit. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Fri Oct 22, 2004 9:59 am |
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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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While I'm admittedly biased (being the designer of the IBC), I dont know of any cheaper alternative that can do what the IBC does, or else I'd be using it !
Yes, they are one of the more expensive parts in your robot, but they are also the key component that turns a bunch of wires, batteries and motors into a remote controllable machine.
There are cheaper alternatives, but they all have some significant disadvantages to take into account..
Servo switches are the cheapest, but are fiddly to make, prone to mechanical failure, have no variable speed control, no mixing of throttle and steering, no failsafe (making them illegal for compeition use), no braking and no weapon control.. quite a list of disadvantages.
Drill-Trigger speed controllers are even fiddlier to make, but add variable speed control and a simple failsafe function, although they can only operate over a very narrow voltage range and still have the rest of the disadvantages of the servo switches.
Probably the next best step down from an IBC is the Electronize controllers from the UK..
http://www.electronize.co.uk/model_electronics_frames.htm
. They use a single mosfet with relay reversing that makes them cheaper to build, but have the occasional problem of relay contacts welding together. You need one per motor and still would want mixing and so on, but some radios can do this..
There is however, a reason that practically *all* competitive combat robots use an ESC (Electronic Speed Controller) of one sort or another.. Most of the alternatives just dont work reliably.. Ask Jeff (Singularity's Driver) how many of his early losses were due to home-made switch-controller failure (and he's very electronics capable).
An ESC, Radio, Batteries and Charger will likely make up 80% of the cost of your robot to start with, but if you look after them, you should only need to make that investment once and hopefully its the cheap stuff (metal, wheels, drill motors etc) that gets broken and needs replacing in most matches. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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Mon Oct 25, 2004 1:57 pm |
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