Joined: 30 Mar 2006
Posts: 111
Location: Sydney, Australia
Yeah i've done the sums, and your right, its going to be just as expensive to buy the bits, as it would be to buy the kits of the electrozine kits, so thats the way i'm leaning at the moment.
I can see that the thought is very much don't do it, so i will most likly buy the electrozine kits. But thanks for the help and advice.
I will probably come back to it at some point, and see if i can do something, but to get a first bot up and running it isn't economical
Mon Apr 03, 2006 4:45 pm
Damien (not Damian)
Joined: 15 Sep 2005
Posts: 327
Location: The other side of The Wall...Melbourne
I've heard drill motors are good. But are they fast and powerful enough for a featherweight rammer? _________________ It seemed like a good idea on paper...
i was thinking of a cheap way of making a variable speed controller because the drills im using do not have variable speed triggers and this is what i came up with
[/img] _________________ WHEN YOU GO TO COURT YOU'RE TRUSTING YOUR FATE TO TWELVE PEOPLE
WHO AREN'T SMART ENOUGH TO GET OUT OF JURY DUTY
what do u think _________________ WHEN YOU GO TO COURT YOU'RE TRUSTING YOUR FATE TO TWELVE PEOPLE
WHO AREN'T SMART ENOUGH TO GET OUT OF JURY DUTY
Tue Dec 05, 2006 11:47 am
dyrodium Experienced Roboteer
Joined: 24 Aug 2004
Posts: 6476
Location: Sydney
I'd bet the pots would overheat uber fast, that's just a complex variation of a mechanical speed controler, the old versions people used to use in rc cars. I think big Al uses this, but has trouble with it catching fire and such...
On a similar note, im developing a cheap esc for my lightweight... will have some more info on it soon, it involves aspects of both el bravo's, AND vertex's awesome speed controler. _________________ ( •_•)
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
That will work only for *very small* motors. Big ones will smoke your pots
The problem is, the resistance of the Potentiometer dissipates unwanted power as heat.
So, if for example your 12v motors would normally use 20amps at full-power (240 watts), and you want to reduce it to half, then you need to get rid of 120 watts worth of heat.
Imagine your potentiometer glowing brighter than a 100 watt light bulb and you will get the idea.
PWM Electronic Speed Controllers work by pulsing full-power at the motor with variable timing to control the speed. That way, any unwanted power is never sent to the motor..
When using resistors, the power is still drawn out of the battery, it is just burnt up as heat before it gets to the motor. Not very efficient for battery life either since any power you dont use is still being consumed/wasted.
Thats why resistive speed controllers are only effective for very small motors. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Tue Dec 05, 2006 12:01 pm
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
I want a valve based ESC, no pesky smoke to worry about then. And it'll look cool. Cmon if they can make a mercury vapor arc rectifier take 10's of thousands of amps..... ;-> _________________ Mechanical engineers build weapons, civil engineers build targets
Tue Dec 05, 2006 4:49 pm
Spockie-Tech Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
Interesting Idea.
I've been tinkering around with Valves recently (Nixies and DekaTrons), but I dont know anything about high current switching with valves.
I imagine it wouldnt be easy, since stopping an arc without something to interrupt the power supply is difficult. What do the tesla coil guys use ? Still rotary spark gaps ? _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Tue Dec 05, 2006 5:38 pm
Rotwang Experienced Roboteer
Joined: 15 Jun 2004
Posts: 1589
Location: Vic
You wont to talk to the coin squasher guys.
Tue Dec 05, 2006 6:03 pm
dyrodium Experienced Roboteer
Joined: 24 Aug 2004
Posts: 6476
Location: Sydney
Jake remember we were talking about that back at PnP a while back lol.
I still don't know what's the problem with people buying a beetle esc, they're cheaper than most rc car esc's and are a one off thing (unless you're a n00b and blow it up first off)
... glen XD _________________ ( •_•)
angus different type of valve lol.
We mean the old style things that look like light bulbs. _________________ Mechanical engineers build weapons, civil engineers build targets
Wed Dec 06, 2006 9:38 am
Fish_in_a_Barrel
Joined: 30 Sep 2006
Posts: 673
Location: Perth, Western Australia
The tesla coils and coin crushers are run from capacitors so they don't need to interrupt the current - it drops to zero all by itself.
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