Quote:
Originally Posted by GeeTwo
I'd never heard of this, and a bit of web searches about the old centronics port leads me to think that the PC-side hardware was not made to support PWM; whether it would be possible to hack it with a tight loop that shut down the PC for any other purposes is probably hardware dependent. Has someone actually done this (using passive components, which was my meaning)?
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Ether did PWM 'bit banging' of the handshake wires on a serial port:
http://www.chiefdelphi.com/forums/sh...52&postcount=1
I used to play .mod MIDI files on a parallel port justing just a resistor ladder and a capacitor to couple still have that stuff somewhere and that was on a Intel 80386 DX 16MHz. That's complex analog audio at up to 15kHz. So yes I am sure if I sat there with some C code I could control several FRC PWM speed control on FreeDOS. I would not attempt this in on any Windows NT kernel because you need a kernel mode driver. It is likely possible on BSD/Linux.
DOS runs in real mode. You will not block the timer interrupts or other interrupts doing this. I used to run this silly trick even with EMM386 running and Windows 3.11.
HighTreason take it away old school...
https://youtu.be/4KUdBgg8Oe4
Then again....I still maintain Commodore 64 code I wrote....so I am pretty dusty.
Quote:
Originally Posted by GeeTwo
Heat dissipation is a big issue here, unless you're talking about replacing the spike rather than a speed controller. The amount of electrical isolation demanded by FIRST is also a steep challenge. I expect brush-less motors and controllers to be FRC legal before single-chip brushed motor speed controllers. I'm not holding my breath on either one.
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The heat dissipation of any single part in an FRC robot is no where near the heat dissipation of the big IGBT we used to charge Navy submarine batteries with this big charger we built. The base of the integrated package is metal and you torque the package to the heatsink plate with either a coupling patch or compound. One of my cohorts left a databook on a board during a test...let's just say we will not read that databook again
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The issue is merely distributing the heat away from the parts that get hot. Either make them more efficient or make the removal of heat more efficient. Same reason we could fill power supplies up with canola oil....as long as you do not let the pressure build or reach the flash point it will not conduct but it will make the heat distribute around (do not try at home kids). That silly trick allowed almost double the wattage from a power supply. By the way - TDI in Hackettstown, NJ was selling a design like this actively before AstroDyne bought them.
There was a time when people argued no FRC speed control would last without a fan either. Power MOSFETs keep getting better and better. Lower the switching losses and on state resistance enough and the heat dissipation will follow. Just please do not do it with silver in the semiconductor die (let's just say it makes the power semiconductors go bad eventually and leave it there).