OK, values, sorry for not putting them on there. The resistor network on the far left side of the schematic is a standard voltage-divider for doing a low-cost....ok.....I JUST MESSED UP (proving my point about getting schematics directly from the internet). There are a LOT of things wrong with this schematic. That;s why you breadboard first before doing anything real.
The voltage-divider is going the wrong way. What you need to do is a step-up optoisolator (or SSR which is just a bidirectional optoisolator on the output stage) to step up the 3.3V to the 5V necessary for that "zone". Hang onto the voltage-divider discretes network through because you might want to pass your PIC's TX back to the BBBW (move the voltage-divider down one pin (from pin 7 to pin 8) on the PIC to its UART TX and feed it to the BBB's UART_RX) to pass any "status" information back (I think its overkill but oh well...you don't need status from your external MCU...traces too short). OK the resistor values on that discretes network can be found in my voltage-division post. I'm pretty sure about the values, but test, test, test. OK, your "series" resistors can be obtained by our reference MOSFET design (which has a problem to, I think its blowbacks are backward backward, AND its battery is backward too...maybe). Its value is 100 ohms. Your "bypass" resistors (between the source and gate on your MOSFETs) is 10K ohms. This is necessary to satisfy the local network requirements for your transistor usage, with it being a low enough resistance that we can trip the FET in switching mode yet high-resistance enough that small enough current that we aren't paying anything for triggering. I tried to integrate the reference design's pot voltage-divider to ADC so we could have variable speed on test, but the particular PIC I'm using doesn't have ADC, so I just wired a switch that will bring all channels up to 20% PWM. Just flick it (even without the BBB attached) to power up your motors to test. Just use a small toggle switch. XTAL is 20 Mhz (unless the PIC I'm using is old-style, which I think is 4 Mhz). Try to get an MCU with 20 Mhz though, the faster the better. PWM should really be done at about a few 100 hz at least to iron out the power transfer. You do this in PIC firmware by counting the instruction cycles in your source code x your crystal speed). 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/e462f298-a74f-4d95-89f6-c3ec9e7681b2%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
