computer-driven fans

[snip...snip...]

Which processor? I seem to recall seeing some that automagically (when properly initialized) continuously cycle through the ADC ports, dumping the results in a defined memory space. Maybe there's an interrupt service routine that should be running in the background? Insufficient information.

Also suggest that you add a hysteresis band, using something like #define HALLWAY_MAX_ON 35 #define HALLWAY_MAX_OFF 33 ... if (HallwayTemp > HALLWAY_MAX_ON) { speed up the fan else if (HallwayTemp < HALLWAY_MAX_OFF) { slow down the fan }

--
Rich Webb     Norfolk, VA

On Fri, 18 Jul 2008 21:46:05 -0400, Rich Webb posted:

AMD Athlon 64 3000+

I wouldn't want to leave my computer behind when I sell this house, so there would have to be a different target. Does anyone have any notion of what hardware might work for this situation?

Hysteresis is what I think of when traffic caterpillars.

--
Every man sees in his relatives, and especially in his cousins, a series of
grotesque caricatures of himself.
H. L. Mencken

Ahh... Rather larger than what typically comes to mind in the embedded realm. So this is just the operating model and you're intending on running something smaller for the controller?

I can imagine setups based around anything from distributed 8-pin, 8-bit microcontrollers with a few bytes of RAM each (which can do a dandy job of monitoring a thermistor or two and PWM'ing a DC fan or two) up to a multi-gigawhiz, networked and web-enabled embedded Linux/XPe/VxWorks monster with voice control and a really big wide-screen monitor.

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Rich Webb     Norfolk, VA

On Sun, 20 Jul 2008 07:31:38 -0400, Rich Webb posted:

I'm not sure how much memory I would need if I don't do the usual things like #include . I like the sound of 8-pin, 8-bit controllers. How do I find out more? Are they RISC microcontrollers?

Again, I'll want to take my nice monitor with me when I leave this place.

--
The urge to save humanity is almost always a false front for the urge to
rule.
H. L. Mencken

The ones I was thinking of are from this family:

The fan controller was for an enclosure and it set the fan speed using an A/D reading over a thermistor. Took 156 bytes for the program code and no RAM other than the processor registers.

The really small ones don't have UARTS but with their slightly bigger siblings and some interface chips you could setup an RS485 system where they could chat among themselves or report back to a central monitoring station.

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Rich Webb     Norfolk, VA

On Sun, 20 Jul 2008 19:22:57 -0400, Rich Webb posted:

It would certainly seem that Atmel is the norm for AVR RISC controllers. The link didn't have any information about prices. While it looked like the chips themselves are a few bucks, am I correct to think that I would also need a "workbench?"

AVR Startup Package ? JTAGICE-MK2 ? ATSK500+501 ? IAR Kickstart Workbench Price ? 339,00* ? JLINK JTag ICE (unlimited) ? SAM7S64-EK ? IAR Kickstart Workbench Price ? 250,00*

My question is what is the minumum cost of entry? I saw other numbers that were ten times as much.

--
A newspaper is a device for making the ignorant more ignorant and the crazy
crazier.
H. L. Mencken

I didn't tried it (I have some AVRs, but no time so far to try it), but looks like this is a free and good tool:

You can build your own programmer, but it is not expensive to buy one, e.g. from

. An USB programmer costs less than $50 and a header board with an ATMega16 costs $22.95. So minimum cost entry would be less than $100.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

Minimum cost depends very much on what's hiding in your junk er ah spare parts bin and how much you're willing/able to spend the time to roll your own.

A minimal startup would need just a chip, breadboard (plus power, connectors and so on), an in-system programmer, and the free AVR Studio available from Atmel. There's also WinAVR (a gcc port)

that plays well with Studio.

The in-system programmer is within the capabilities of end-users to build but the standard AVRISP Mk2 (USB interface) is only US$36 and that removes one variable when first starting out. Add an ATmega168 (16K flash, 28-pin DIP) for another US$4 and you're good to go.

The STK500 is a stand-in for a breadboard + ISP, having sockets for all of the DIP-flavored AVRs. Its programming headers can also be used to program devices off-board (e.g., on a breadboard).

I'm not a huge fan of ICEs and they're certainly not necessary for a minimal startup system. The AVRISP is quite sufficient to load code into a device and get it running.

One caveat here: Most (all?) AVRs with internal RC oscillators come from the factory with their fuses set to use the RC as the system clock, typically at 1 MHz. The ISP programming clock should be set to no more than 1/4 of the devices clock speed. If one doesn't realize that the device is running from the internal oscillator, instead of the 14 MHz xtal that's hooked up, the chip can appear to be faulty. The solution, of course, is to lower the ISP speed to below 250 KHz in order to communicate with the device to set the fuses to use the external clock/crystal; after that, the ISP speed can be set higher if desired.

On the compiler side, I've been using Imagecraft for years and am quite happy with them. They also offer an AVR starter kit (compiler included) that may interest you.

is a super resource with links to other compilers, kits, tools, ...

One last thing. The SAM7 chips are ARM7 devices (32-bits). They're quite nice as well but do be aware that it's a different family.

--
Rich Webb     Norfolk, VA

On Mon, 21 Jul 2008 10:40:51 +0200, Frank Buss posted:

Then I'm in. Do you have a header board?

--
Democracy is a pathetic belief in the collective wisdom of individual
ignorance.
H. L. Mencken

On Mon, 21 Jul 2008 08:55:29 -0400, Rich Webb posted:

I'd like to say that I understood everything you wrote here, but it wouldn't be true. Please don't confuse my misapprehension with ingratitude.

Thanks again for your generous response, Rich. I'm downloading WINAVR and will ask a more-focussed question on a new thread.

--
Let's not burn the universities yet. After all, the damage they do might be
worse.
H. L. Mencken

Heh. No worries, just tuck it in the back of your mind. One day you'll be trying to program a brand new AVR chip with the same setup that's worked flawlessly for your "lab rat" development chip and then wonder WTF why the new chip isn't even recognized by the programmer. ;-)

--
Rich Webb     Norfolk, VA

No, I have just some chips, but you can buy some:

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de