side note: i've always wanted to make a flipper that fires automatically (in addition to on radio command) by having a button strategically positioned on the flipper itself that fires it off if you happen to have the opposing robot contact it.
This is because you usually have fractions of a second to perceive the opposing bot is in a vulnerable position, react and fire
any lag between firing and the actual release of the flipper will be fatal here too
im aware you're not planning it as a flipper but the principle is the same _________________ <Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls
Mon Sep 19, 2011 11:25 am
frogbiscuit
Joined: 26 Aug 2010
Posts: 82
Location: Wollongong
12V motor on 18V? really??
I know DC motors can take 110%, but 150%? Too chicken to try that without a temp probe on the motor.
Good call on the auto-recock. Fully intend to automate. Right now just motoring manually to cock & fire positions with forward & reverse pushbuttons. No time for such in a real fight. In future, one button to fire and then auto-rewind the 6 C-135 Bunnings springs. Could o' would o' should o' ...talk is cheap til I can put metal on deck.
Grandiose plans for sensors, optical and tactile. Farnell has cheap "sounders", piezo devices tha twork great as hair folicles.
Mon Sep 19, 2011 8:54 pm
Knightrous Site Admin
Joined: 15 Jun 2004
Posts: 8511
Location: NSW
quote:Originally posted by frogbiscuit:
12V motor on 18V? really??
I know DC motors can take 110%, but 150%? Too chicken to try that without a temp probe on the motor.
Hehehe, still stuck in that "Uni Robotics Theory" mode How much you can over volt a DC motor is really dependent on it's construction and design. Some motors like the 12v scooter motors happily run on 36v without deathly results, others just fry from nominal voltage use Although a temp probe on the motor is pretty good in theory, it's not as effective in practice. Especially with brushed motors, by the time the motor can heats up enough to trigger your thermal threshold, the armature can have already smoked, cooked and died spectacularly. And the other side of it, most builders would rather fry a speed controller or motor then be limited by software and control systems when ham fisting it out in the middle of a heated battle. _________________ https://www.halfdonethings.com/
Mon Sep 19, 2011 10:46 pm
haz
Joined: 15 Aug 2011
Posts: 169
yes they can be run at 18v, i am in my featherweight with no problems
Tue Sep 20, 2011 1:13 am
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
Thats seriously cool, got any pics of the mechanism itself?
Drill motors are always finicky but giving an educated guess you could try 18v on that pretty safely. the motor doesn't sound all that loaded. When you stall them out they instantly start pouring out smoke though, so you'll want to avoid that at all cost with some limiting switches or something like that.
The linear actuator is out of it right now being worked on, that actually makes it easier to see the mechanism.
Sun Sep 25, 2011 5:24 pm
frogbiscuit
Joined: 26 Aug 2010
Posts: 82
Location: Wollongong
Define "...instantly..."
Like within a second of stalling? So a rotation detector would be better than temp probe?
Yeah, guess I'm stuck in retardo roboto 101...
Sun Sep 25, 2011 5:44 pm
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
if your keen on doing it mathamagically you need to model the efficency of the motor, its heat disipation Vs ambient and RPM.
Also you need to measure amps and volts in.
At sane voltages your not going to explode the brushes in one hit or arc through the insulation.
As such you work out how much energy your putting into the motor vs how much its putting out and the left over is heat.
You want to keep the armature < ~100C and the magnets < 70 or so max.
Combine all that with a thermal probe to correct for drift in your model and you have the best current limit you can do.
I'd say you can go to 3x volts and 2x amps with a drill motor, but not at the same time ;-P
Too many amps and the brushes explode too many volts and they get eaten by sparks.
too many amps*volts and the winding cooks _________________ Mechanical engineers build weapons, civil engineers build targets
Sun Sep 25, 2011 6:05 pm
frogbiscuit
Joined: 26 Aug 2010
Posts: 82
Location: Wollongong
Progress:
Established radio link. Motors turn wirelessly.
Upgraded PICs from 877s to J50's.
Full circle on encoders. Back to incremental, with neutral channel.
Weapon now with auto programmable load-cock-fire positions.
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