Need small micro dev kit

The text below was part of an ongoing thread that I was participating on another board. Some of the members on the other board asked exactly what I was wishing to accomplish so the topic is treated in more detail than most. I'm still looking for a small (INEXPENSIVE) kit

I want to develop an inverter to take a 200v dc bus and convert it to

120vac. I will use 4 mosfets configured in an H configuration. By controlling the switching trajectory of each fet the output will be sinusoidal in shape. Of course there will be some switching garbage in the way of harmonics that I will have to deal with. A mosfet will allow a carrier switching rate of say 20kHz no problem - the faster you switch the higher will be the spectrum of harmonic trash that needs to be filtered. So then the faster you switch the easier the filter design becomes. A switching rate that is an exact multiple of 60Hz would be good so that the carrier and the fundamental components can be synchronized - called synchronous pwm. This may be easier to implement with a small micro.

The 200v dc bus will probably come from 4 car batteries connected in series. This will go into a full bridge phase shift converter running at 100kHz or so - I've got a couple kicking around here that I have already built. The

200v bus can be regulated to within a gnat's ass, so the sinewave inverter can run open loop without having to compensate for bus voltage variations.

So what the micro has to do is output the pwm routine to drive the 4 mosfets. This could be as simple as a counter and a table with the pwm times stored. Go to address 1 and load that number into the counters(and the info for state latch as well). Count down to zero and go to address

2 and load that number into the counters. Perhaps there are 200 (for a 12kHz carrier) address that store the timing and state information for one sinewave.

There are only 4 possible states with the inverter while it is running.. Top right and bottom left both on. Top left and bottom right both on. Both top on, or both bottom on - each called a zero state. Only other possible state is all fets off, but that is never used while the inverter is running. Never are the top and bottom transistors in the same pole on, because that would put a direct short across the bus.

My microprocessor skills are almost non-existant so I am looking to getting my feet wet. Whatever platform I choose (based on you guy's input) it should be above everything else easy to learn. It must also have the computing power necessary to do the pwm routine. I'm basically looking for somebody to tell me to go to digikey and order such and such a kit.

thanks Bob

Reply to
Yzordderrex
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Hmmmmm..... sounds like a DarwinAwards project, go for it...

martin

Reply to
martin griffith

Andy writes: I like the PIC 16F84 . It is cheap, has a 20mhz clock, and draws about 5 mils --- costs about 5 bucks... Has on-board EEprom memory and versatile built-in I/O . I've used it in several ham projects...

Lots of PIC versions are available, and there are development kits and programmers for sale very cheap. Many have built-in A/D converters.

Also, a BASIC compiler is available....

It isn't the fanciest one, but for one-chip applications it does a fine job. Just google up some info on it and plan to spend a week or so learning to program it. It has a simple machine instruction set. And a simple BASIC instruction set for the BASIC compiler.....

Good Luck, Andy W4OAH

Reply to
AndyS

Since when are car batteries 50V?

Reply to
a7yvm109gf5d1

New cars are supposed to be built with 42 volt batteries before long. The charging voltage would be about 48 volts.

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Reply to
Michael A. Terrell

Good point on the 48v charging system there Mike. I'll probably need an alternator someday. This system could actually make a nice standby power system to keep the furnace & radios running when power goes out.

Sorry, I forgot to mention that I am a power EE. I design large inverters for a living. I've got a handle on the power side of things like deadtimes and thermal management and so on - I'm just lacking on the micro end of things. That's basically the whole motivation for this project - a learning experience. I'm taking a 6 month sabbatical from work and I would expect my next employer is going to want to know what I did on my little vacation. If I end up with a piece of hardware that might be useful then so much the better.

Ok on the pic Andy. I like hearing words like Simple & Basic. I'm a keep it simple kinda guy. I'll look into that micro for sure - that's the answer I was looking for.

Got my DD214 too - I'm just another tin can sailor outta Pearl :-)

73 Bob N9NEO

Michael A. Terrell wrote:

Reply to
Yzordderrex

Did you happen to notice that most people bottom post on this board?

Don Ex-W7SAT

Reply to
Don Bowey

Yzordderrex TOP-POSTED (also BREAKING THREADING and ignoring context): ...and just for kicks changed the Subject line to something without meaning to anyone else.

:: Andy wrote: ::I like the PIC 16F84 ::

The PIC 16F84 is ANCIENT. If you can even find one, it will cost you more than a newer, more able PIC variant.

Opinions differ on the "simplicity" of PICs. One of my favorite descriptions of the PIC:

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*-*+PIC+orthogonal+toolsets+header-*+*-*-*-*-PIC-*-dead+Banking+Paging+thirty+free+horrid+violated+JTAG+*-*-Holy+*-*-*-addressing-modes-*-*-*-*-*-*-spin+*-*-painful-*+*-*-em-*-*-*-*+immediate-addressing+A-good-place-to-start

Scroll down Lindan's post and look at what he has to say about the AVR.

Note: That group (comp.arch.embedded) is the place to ask questions about microcontrollers.

Reply to
JeffM

You can get motor control pic/mcu wich have the pwm module with the sine lookup table already. Im using a dspic30f2010 16bit with 3ch pwm wich would be able to do it easily.

Colin =^.^=

Reply to
colin

Good for you! :-)

Did you take advantage of the free meal at the Golden Coral restraunts yesterday? I went, but their Monday menu isn't my favorite. :(

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Reply to
Michael A. Terrell

Hi

Look at

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ADUC702x is my favorite. PWM-Features included for gate-driving... AD and DA 12 bit @ 1 MSPS 40 MHz ARM7 core. Kits from $30 up to $279 (with usb-JTAG included) where available (in january 2007:-(

Marte

Reply to
Marte Schwarz

Sure did notice that most bottom post here don.

73 NEO

D> On 11/14/06 9:59 AM, in article

Reply to
Yzordderrex

Thanks for comments Jeff. And Yes, I'll be the first to admit I have a lot of bad habits when it comes to posting on these forums. I've had them a long long time and expect they will accompany me to the grave. Thats ok with me.

When I changed the topic I was calling Andy directly to thank him for the input. Andy told me to take a look at the Pic products, not just the 16F84 in particular. I have heard others on other boards rave about the Atmel parts and I am sure they make a nice part. I know they have a large following. I am leaning towards the microchip products for two reasons. I have found an application note that does exactly what I need to do. I also have remembered that I worked with another engineer many years ago that is well connected with microchip. He in an independant consultant and writes application notes for them. I have been in contact with him recently as he was looking for some information from me. I will of course take a close look at the AVR parts before making any decisions. The main criteria is cost and time to learn. I'm presently in between jobs on a self imposed sabbatical and I'm looking for some resume building exercises.

Thanks again for the input and if I have any Qs as the development effort goes forward I'll be sure to post to comp.arch.embedded. Below is a link to an inverter app note.

73 Bob N9NEO Just Say NEO!

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JeffM wrote:

formatting link
*-*+PIC+orthogonal+toolsets+header-*+*-*-*-*-PIC-*-dead+Banking+Paging+thirty+free+horrid+violated+JTAG+*-*-Holy+*-*-*-addressing-modes-*-*-*-*-*-*-spin+*-*-painful-*+*-*-em-*-*-*-*+immediate-addressing+A-good-place-to-start

Reply to
Yzordderrex

Nope, we don't have that restaraunt up here in MA. No Waffle House either that really bums me out. Mabe WH next week when wife and I travel to PA to see her pappy.

regards, Bob

Michael A. Terrell wrote:

Reply to
Yzordderrex

"Virginia is for Lovers", Florida is for ol' farts ;-)

...Jim Thompson

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Reply to
Jim Thompson

And continuous top-posting is for rude people.

Reply to
Don Bowey

And you are SO jealous that we're accepted here, aren't you, Jim?

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Reply to
Michael A. Terrell

Arizona is for ol' farts, too ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Yours are all dried out! :(

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Reply to
Michael A. Terrell

I am doing a project with the PIC16F684, which I think is similar to the F84, but it has a built-in PWM that can be configured as a four-channel H-bridge system. It is in a 14 pin DIP package, and can be programmed using the PICkit1, which is about $30.

My project is a boost converter using a switched inductor to generate 800 mA at up to 50 VDC, from a 12 VDC source. I have simulated it using LTspice (Switcher CAD), and I was able to get up to 90% efficiency. I will be breadboarding a prototype soon. The design is scaleable to almost any voltage and power level. If you use this PIC, I can help you with source code and debugging, but I am using assembly code.

I also have a project on the back burner for a three phase low voltage motor controller, for which I will use a higher level PIC such as the PIC18F2331 and the like, which have six or more PWM modules. I have a C compiler for the 18F series that I might use, although I find well-documented assembly code is fine for low-level stuff. For higher-end projects a debugger like the ICD2 is a good investment at about $150.

Good luck, and be careful

Paul

Reply to
Paul E. Schoen

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