Let us look at these motors again. A lot of you are doing (well, thinking of) drone projects so let's talk a little about my little Beagle and thick-conductored "hot" motors, How we get them making sweet electric love with each other.
Ok what you do is you feed off of one of your PWM or GPIO lines of your favorite beagle. Both have their downsides. Hardware PWM is lacking a certain jeun-se-quoi, its just a little too digital (those that have worked with it before know what I'm talking about). However software-based PWM (how motor speed control is done) via GPIO I would surprised is good on a multitasking OS environment like UN*X. Maybe with interrupts...idk. Of course my solution is elegant. I went out and saw how fast I could get a UART to go, apparently 128K baud...this is acceptable. What you do is you use a slave PIC16Fx (the F means flash btw) and I run a 5V zone next to my Beagle's 3.3V one. The beauty of this approach is I've decided that I'm going to drive these motors DIRECTLY off of my Nickle-Metal Hydrides, no caps just spread my error over an inductive domain than a capacitive one (***knowing look***). Can see my new buddy, Graham, wondering if he should whip out the old complex numbers on this assertion. Can you do ESC direct from GPIO or PWM off of your Beagle? I suppose. And you might try it. Just pull directly off of a PWM line and feed it to the SSR at the front-end of what I'm talking about. I am not adverse to it other than the whole getting UN*X to do it. Maybe one of Lidia's sitaras (I mock) and that PRU to do it. In fact, I would suspect, that that's the whole point of the PRU issue. So you get your PIC to accept on its hardware UART a byte of which motor speed you want to control (I need to control 8). Then I send it an int (2 bytes) with how long on it is, and then an int of how long off it is. And just implement it in a software loop completely bypassing the PIC's hardware PWM as well. It just drives 8 GPIO's leading to nice multi-stage ESC. We feed this nice PWM signal to the SSR's which drive directly to MOSFET, and accept for the blowback rectifier, we are going to run this bare-metal as they put it (semiconduction aside). "You can do it this way?" Its me, dear, I wouldn't steer you wrong. OK so let's look at the power train. We have 1.2V NmH's strung in series to give us about seven volts of beefy power (and we have the same number of cells as our motors) so I'm just going to say 2.5 Amp hours of juice (the rating of one cell). We use our stock BBBW to communicate with the PIC (that's actually doing the speed control) via probably optoisolator-step-up, to custom programmed 5V PIC and then we just pull of its GPIO to cheap SSR direct to cheap MOSFET direct to beefy motor. I so know this will work. Somewhat improper I'll admit, however life isn't perfect. I can just tell this has the characteristics I likey. :D I'll put up a schematic, maybe even a PCB, of what I'm talking about here (tested) so you can use these little drone motors easily. Theory: you'll find these ones come in 2.2KV and 1.0 KV. I'm hoping my advisors have instructed me correctly that with the battery type I'm using, connection, propellers bought that it will transfer my battery power to nice upward force linearly and predictably. I got a grip of 1.0KV ones. the KV rating pertains to the RPM per volt. So a lower value would mean less RPM's per volt, a higher higher RPM's. From an engineering perspective what you want to do is look at the whole power subsystem seeing that you get a tight linkage between your power source and actual FORCE generated by the propellers. You can't just say the 2.2KV ones are "better" or "more powerful" or you might end up with a system that's electrically perfect but just doesn't transfer power right. Anyways...in conclusion...(UART to external MCU) to SSR to MOSFET direct to motor. Or PRU to SSR in previous description. On Monday, January 30, 2017 at 6:19:30 PM UTC-7, woody stanford wrote: > > I posted the remote control for this in Software, but I put a bunch of > hardware in it so I thought I'd post it here. > > > https://groups.google.com/forum/#!category-topic/beagleboard/software/evSIUcuWfUY > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/8c24059d-7c0a-4942-bcb6-56fcf181ffe1%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
