Wanna fight?
by Pev
Wed Sep 20, 2006 11:17 am
Awesome, but I have to ask, does it help him stay upright? I was thinking in a newtonian manner as a spinning disc will act like the gyroscopes we had as kids and will always try to maintain an upright position, or atleast maintain the orientation that they were originally spung up in. (hope I am remembering my school physics correctly it has been a long long time lol)
Anyway would be interested to know what effect it has if any
Pev
Anyway would be interested to know what effect it has if any
Pev
by beermat
Wed Sep 20, 2006 4:37 pm
h3dude - the motor is a 'pancake' electric motor about 1.5" in diameter. I have it powered from PWM port 1, with a resistor in series to limit current draw (mostly concerned with stall current if he falls over). The motor shaft is 2mm, the hole in the center of the blade is 11mm, but I discovered a propeller shaft adapter for electric R/C planes designed for mounting things with big holes onto small shafts. Oooeerr missus.
Pev - interesting point. I haven't had him move around too much yet (wooden floors + spinning metal blade = night on the couch), but I'll play around later on a foam mat, see what happens. I definately 'felt' the push-back/resistance from the spinning blade when holding him and tilting him, so there is definately a gyroscopic effect here that is more than negligable. Section 2.8 of this article I just Googled is relevant to this topic.
Pev - interesting point. I haven't had him move around too much yet (wooden floors + spinning metal blade = night on the couch), but I'll play around later on a foam mat, see what happens. I definately 'felt' the push-back/resistance from the spinning blade when holding him and tilting him, so there is definately a gyroscopic effect here that is more than negligable. Section 2.8 of this article I just Googled is relevant to this topic.
by Bullit
Wed Sep 20, 2006 8:45 pm
You say you have the motor powered by the pwm port? Or do you mean you have a rc speed controller that is connected to a pwm or servo port? I would think powering the motor off the pwm port could be bad. I would think that an r/c speed controller could be placed on any of the servo ports or the pwm port.
by beermat
Thu Sep 21, 2006 12:58 am
Bullit, what is your main concern about going directly from the PWM port without using an ESC? PWM for DC motor control is not new, though it's a bit primitive? Various documentation on the MR-C3024 mentions the 3 DC motor ports. Am I mis-understanding something? The need for a BEC, for instance?
by Bullit
Thu Sep 21, 2006 2:15 am
The PWM's are putting out current from the mr-c3024's onboard regulator which is something like 350ma total. I think that they intend that you will use this output to drive a transistor which will switch the battery rail to a dc motor. You can make a small circuit with a few components to do this. My concerns are that you will either damage the ATMega128 or the regulator without a transistor to handle the load of a motor. The up side is that switching the battery rail you can put more voltage and power to a motor.
by beermat
Fri Sep 22, 2006 1:19 am
Gotcha! I have the same concerns. At the speed it is spinning right now, current draw is less than 100mA, so I'm safe. That will increase at a higher spin rate and/or with some resistance when I start cutting things, at which point I was going to move onto a different method of motor control, along the lines of things you have previously mentioned. Right now, though, it's still fun to have the fiance freak out about it as it is! 
