Need small micro dev kit

Yzordderrex · 2006-11-14T00:22:08+00:00

The text below was part of an ongoing thread that I was participatingon another board. Some of the members on the other board asked exactlywhat I was wishing to accomplish so the topic is treated in more detailthan most. I'm still looking for a small (INEXPENSIVE) kitI want to develop an inverter to take a 200v dc bus and convert it to120vac. I will use 4 mosfets configured in an H configuration. Bycontrolling the switching trajectory of each fet the output will besinusoidal in shape. Of course there will be some switching garbage intheway of harmonics that I will have to deal with. A mosfet will allow acarrier switching rate of say 20kHz no problem - the faster you switchthehigher will be the spectrum of harmonic trash that needs to befiltered. Sothen the faster you switch the easier the filter design becomes. Aswitchingrate that is an exact multiple of 60Hz would be good so that thecarrier andthe fundamental components can be synchronized - called synchronouspwm.This may be easier to implement with a small micro.The 200v dc bus will probably come from 4 car batteries connected inseries.This will go into a full bridge phase shift converter running at 100kHzorso - I've got a couple kicking around here that I have already built.The200v bus can be regulated to within a gnat's ass, so the sinewaveinvertercan run open loop without having to compensate for bus voltagevariations.So what the micro has to do is output the pwm routine to drive the 4mosfets. This could be as simple as a counter and a table with the pwmtimes stored. Go to address 1 and load that number into thecounters(andthe info for state latch as well). Count down to zero and go to address2and load that number into the counters. Perhaps there are 200 (for a12kHzcarrier) address that store the timing and state information for onesinewave.There are only 4 possible states with the inverter while it isrunning.. Topright and bottom left both on. Top left and bottom right both on. Bothtopon, or both...

Nov 14, 2006 22 Replies

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jasen 19 years ago

have you programmed anything in any sort of assembler before? how about C?

look at the free documentation for the different devices, pick the one that makes the most sense to you.

this sort of task sounds like to could be done using a $3 microcnopntoller chip and a few dollars worth of extra bits.

A setup where the chip can be reprogrammed while still attached to the device is desirable. especially if you get the program wrong a few hundered times...

Bye. Jasen

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Yzordderrex 19 years ago

OK Jasen thanks,

I ordered the pickit2. It is as good platform for about 50 bucks. There is a one day seminar down the street from me in a week or so. I am in-between jobs so this should be a good resume builder as well as fun project.

thanks Bob

jasen wrote:

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