AVR-Chat

--- In AVR-Chat@yahoogroups.com, "William Nachefski" 
<slaphappysamy@y...> wrote:
> 32LBS!  Wow thats alot of boost.  I run my chevelle on 18 lbs, and 
> thats as far as I dare go.

Heh, yeah.  I run daily at 21-23lbs, and track at up to 28lbs.  
Depends on the track.  The turbos max out thermally at around 23lbs 
anyway - 2lbs gains boost but at a tremendous cost in heat and 
efficiency loss to heat.  Good for twisties, only good for a short 
time on the straights.

32lbs on a warmed up but not track-heated engine is a rush.  
Once :)  Then I get into a buddies 890 RWHP monster, and we can suck 
the headlights out of the Porsche Turbo with our wake-vacuum as we 
go by.  Fun fun :)  Oh, BTW, these are all daily-driven full-
interior street Supras.  Not trailer queens.

To keeps things AVR related, I'm working on the 2nd design spin of a 
vehicle datalogger, learning from the first one.  The original was 
discussed at length on avrfreaks.net, and the design morphed several 
times from that.  Basic features were/are :

AVR Mega128 based
16 (now 16 or 32) analog inputs, 0-14V, 0-5V, 9-14V
6 digital inputs
I2C temp sensors, any number (er, say 16 max)
Serial input for GPS logging
ADXL202 2-axis G-sensor
USB
MMC card for data storage
RTC for time-stamping of data
Simple LCD screen

Things I've learned ...

- Optoisolaters can take way too much current from the signal being 
measured.  Use an opamp buffer instead.

- Power spikes on the +12V line can be murder.

- Solid, quiet power supply section design isn't as easy as it looks.

- Mixing analog and digital on a single board is hard.  Really hard.

- 2 layers may be a lot cheaper, but it forces some bad compromises 
in layout.  See previous point.

- Believe it or not, 3mm of plastic bezel between the  alum endcaps 
and the alum enclosure actually makes a difference in EMI.  Go metal 
to metal instead, even if it's not as pretty.

- DB25 and DB37 leak EMI too.  Dang, means to do it RIGHT, we need 
those expensive AMP connectors.  Hmmm, shielded DB pcb connectors ?

- There is no perfect EDA software.  They ALL have bloody blasted 
quirks.

- Changing EDA software is a pain.  I use Protel 99SE, which has its 
own share of quirks and bugs, and I'm getting tired of them.  Protel 
DXP is a bloated pig, though it's really really pretty.  Altium 
won't release SP3 for DXP now, rolling into Nexar.  More alpha 
software for us to test, oh goodie.  Pulsonix is nice, but lacks 
features.  Zuken CadStar looks nice, has tons of features, and I 
still can't quite figure it out.  Gotta shake that 99SE bias and 
just relearn I guess.

Dean.