Projectwise...

[dedndave]

you can almost use a box with a light bulb



thing is, it wants to follow a rather strict schedule
the closer you get to it, the better the results

[clive]

The customer was more interested in high G (blunt force trauma) events, than orientation/motion. I did look briefly at free-fall detection with the Freescale demo board.

I think primary customers for the accelerometers are the cell phone companies, and perhaps Nintendo, which might explain the footprints.

[farrier]

vanjast,

My favorite, and most helpful video:

http://www.youtube.com/watch?v=3NN7UGWYmBY

For those who can't solder, and for prototyping:

http://www.schmartboard.com/index.asp?page=products_schmart

hth,

farrier

[dedndave]

a little additional info...

the schedule or "profile" for curing solder paste goes something like this...



what makes it fun is that, for different runs, you may have a different total mass in the oven
of course, it takes longer for larger masses to achieve temperature (hot or cold)
in your case, that is working to your advantage, as you have low mass, and probably a single unit (on the first run)

you want to be sure to leave any melting plastic parts off until after reflow
the balance is:
don't overheat the parts, or keep them at peak temp too long
you have to be hot enough, long enough for the paste to flow

the pre-heat and soak times help get the paste ready to flow without damaging components
the temperature of the board itself is typically monitored - not ambient

[vanjast]

..the temperature of the board itself is typically monitored - not ambient

Yeah! I saw that... nice to catch these little titbits.
I'll get hold of one those tagged sensors that I can attach to the board.

A laser sensor cold be very useful here.
:U
edit: Just figured out that I'll use a PT100 with a CrocClip to clamp it to the pcb - simple

[vanjast]

Been reading/remembering what I studied yonks ago.

I'm using the ST gyro chip with the accelerometer one. After a bit of 'catching up' I figured out that it's possible to implement a 'rate gyro' with only the accelerometer + some maths hashing. The micro sucks about 3mA at 1Mhz, the gyro sucks 6mA standard, and the accello=0.5mA. i can increase the micro frequency to handle the maths (+2mA) and shut down the Gyro in code (~uA)... I actually think the rate gyro would be more accurate  :bg I'll keep the normal gyro, as it would be more usefull with regard to aeronautics.

I can save about 30-40% suction...
Ahhh .. another glass of red for me
:U

[dedndave]

i have had occassion where we were running on the cheap - lol
the company i was contracting to did not have the oven, or even a thermocouple

i added a 1N4148 to the board layout (very inexpensive switching diode - upgrade of the old 1N914)
this part would hardly ever be stuffed, of course
but, for making temp measurements, a typical diode junction is very linear
you forward bias it with a few mA, then measure the Vf (forward voltage drop)
i used an op-amp and a couple pots on a little board outside the oven (one pot for offset, one for gain)
once the pots are adjusted, the diode makes a very nice thermometer
i scaled the output so that the DC voltage could be read with a DVM
to make things simple, i set it up so 1.00 VDC from the op-amp was 100 degrees C, 0VDC was 0 degrees C
it gives a good representation of the board temperature, as it is hand-soldered into it
of course, if you leave it at high temp for too long, the diode solder could flow - lol
but, that isn't likely to happen because you don't leave it hot that long and paste flows before regular solder

other companies i have worked for had all the nice equipment, of course
the commercial ovens are way over-priced, if you ask me
but, they will store several profiles and settings
once you have made the first run and stored the profile, anyone can operate it

[vanjast]

Did a similar thing with airflow measurements.

For consistent reliabilty, it probably better to stick with 'standard' sensors.
:U