the nominations are coming along nicely
I think a week may have been too long - they seem done now
hope people don't lose interest before voting time
at least it's not a 18-month, $300 million election season
no we're a little more sane here
heh - must be the international contingent
the difference is none of us will get rich(er) and (more) powerful if we're elected
hmmm - damn
we'll just have more work to do
can I un-accept? :)
yeah, we're doing it wrong aren't we
there are only 7 nominees at the moment - just expand the board to 7 and it's easy
yeah I briefly wondered what we'd do if we got <= 5
I guess we'd declare them the new board - easy
draw straws for who gets to stay (or leave)
<maddash> i'm merely suggesting, not complaining <---- liar
I suggest that his suggestions look like complaints
someone needs to splain that honey/vinegar/fly thing to him
preferrably his parents, they should have done that a long time ago
it has become apparent that maddash has provided -- at a minimum -- half-truths and misleading statements
no politics on the channel!
it has become apparent that maddash should mostly be ignored
I was just going to mention the bumper sticker "Republicans for Voldemort"
don't blame me - I voted for Roslyn!
wow - 50-pin shielded flat ribbon cable is expensive
why do you need the shield?
this is for a power supply project using the 5i22
the control PC willl be inside the main controls cabinet
not where the actual H-bridges are, but still in a noisy environment
unless the noise is radiated, shielding is less important than interspersed grounds and maybe some ferrite
I think the cable length will be quite short - 1 section of the twist/flat, or 8-10 inches otherwise
actually this stuff looks good: http://www.connectworld.net/cgi-bin/iec/CAB050-RI-TW
8" between flats (or including flats)
the stuff I sent you is longer, right? 16" or 24" or such?
18 twisted + 2 flat
I'll be using HAL in this project, so I'll have a chance to make sure the 5i22 works (or at least that we have appropriate PIN files)
oh, I missed the 22 reference
only one digit off :)
I'll be making some analog interface boards also - if you have suggestions about making them useful for other purposes, I'll be listening
I have a specific design in mind, dunno if it would match up with what you need
at the moment, I only have 2 specs: 4 or 6 channels of A/D and D/A, at 16 bit resolution
I'm thinking in the other direction - if I can make the design more useful to the EMC/HA crowd
I'm planning 12 bits
because 12 bit converters are cheap and tiny
I recall there's some SOT-23-6 part you like
both A/D and D/A are available in that package, for $3-4 each in single piece quantity
hmmm. if there's a higher resolution version, and they're bipolar, I can use them
not gonna find bipolar in a tiny package
dual supplied need too many pins
there are SOT-8 parts, and 8-umax
there is 16 bit unipolar in a sot23, for $4.50
[01:08:58] <jmkasunich> http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=296-12966-1-ND
dunno sample rate yet
unipolar=no-go in this application
we've had too many problems with edge effects around zero
averaging stops working, and the polarity detection circuitry (and reading it) isn't always synchronized with the analog read
don't follow - if you are using a converter where the input swing is from 0 to 5, you bias the input so zero = 2.5V
sure - you can compress and offset the range, but that isn't how they've done it in the past :)
I can do that on this board though, so that may be OK
you certainly would want to do it as close to the A/D as possible
yes, especially in a noisy environment
the higher the voltage range going into the chip, the happier these people are
my preferred A/D front end is a diff-amp, with the "ground" end of the 2nd feedback resistor connected to the midpoint of the rail
plus you can directly measure it with a scope
what sample rate do you need?
preferred because you like it, or preferred because it works well with unipolar supplies/A/Ds?
not too fast - 10 KHz per channel
100 KHz would be nice though - I may put a slew rate limiter in the FPGA
preferred because these days +/-10V A/Ds are rare, expensive, and dying out fast
my plan for the 5i20 A/D is a 22 bit accumulator to which each sample is added, and a 10 bit sample count that is incremented each time, nominal sample rate 1MHz
hmmm. the ADS1100's are I2C, so they may not be able to share a clock like you would with SPI
at least, not for a parallel-load/read application
so you read the 32 bit word, subtract the 10 bit count from the previous word to get the # of samples since last time, subtract the 22 bits to get the sum of those samples, then divide to get the average voltage over the period since last time
the ADS1100s top out at 120 S/sec anyway
sounds like a good plan
I foolishly selected "In Stock" on the digi-key search, and got only that series
[01:17:06] <jmkasunich> http://dkc1.digikey.com/Redirect.aspx?url=http://focus.ti.com/lit/ds/symlink/ads8343.pdf
4 channels, 16 bit, bipolar, $14ish
yeah - that looks good. thanks
although full scale is a maximum of +/- 5V, not 10
I expect to have a buffer on the card, so scaling isn't an issue
so technically I could shift as well, and use a unipolar chip
worse, +/- 2.5
Vref = 0.5 to Vcc/2
Vin = +/- Vref
yep - found that
checking the 8345 now
oh, 8-channel version of the same thing
I really think you are better off with a single ended A/D
that may well be
all the new A/Ds are being made on digital processes, single low supply voltage
so buy a good op-amp using an analog process and use that to do the shifting and scaling
they always use OP497 - I don't know why
seems like a nice op-amp to me
very nice actually
I never looked it up - just remembered it's on all their baords :)
maybe that's why they use it
very slow, but very precise
given their bandwidth requirements, slow is probably OK
yep, and precise is very important
$7 or so each at DK
thats only $1.75 per op-amp
not bad at all for a high precision part
strange - 2.5mA for the whole package, but I swear I've felt those things get warm before
wish it was faster, I'd be tempted to use them
500 KHz isn't bad
though 150 mV/uS isn't that great
0.05V/us slew rate
150 is typical, 50 is min
ah - I'm looking at the slick-sheet page, not the datasheet
the heating thing - the 2.5mA is just the quiescent current, any current into the load would also contribute
in a low Z circuit, that could be 5mA or more per channel
this application had a 4-20 mA option, and I think the 0-10V mode used a resistor across the output (there's a 0-20 mA option as well)
so I can see a bit more than 2.5mA for the package
I've build a few of those multi-standard circuits, +/-10V, 0-10V, 0-20mA, 4-20mA (4-20 is done in software using the 0-20 hw)
yep - same with this one
this didn't need the bipolar option because there's a fwd/rev output
so why are you looking for a bipolar adc?
well, the input is +/- 10V, and there's a reluctance on the customer's part to use unipolar, due to past experiences
since I can scale and shift though, that may not be a problem. the method used before was to detect the sign, and invert if negative (and run the sign bit to a digital input bit)
yes, and possibly why they're gun-shy about unipolar
"it was dumb before, so we don't like it"
[01:57:21] <jmkasunich> http://jmkasunich.dyndns.org/pics/BipolarAD.pdf
ah - thanks
+/-10V, with 0V at precisely mid-scale
Vref accuracy sets gain error
resistor matching sets offset error
all resistors are identical, best precision comes from a network where all are made at one time and share a substrate (for tempco matching and temp tracking)
ok, so a multi-element respack should help there
sorry - typing one-handed, holding food with the other :)
hmmm - I wonder if htese leftovers were left over too long ago
taste a little "off" ?
hard to tell - it's chinese food
I nuked it for a couple of minutes, so I suspect any beasties are dead
spicy chinese like Hunan? or bland?
probably keeps for a month, so I should be OK
jepler: should M2/M30 set G97?
it does already set G94
I'm almost sure it should, but maybe I'm missing something
jmkasunich, I think it's a language thing - there's a design, but he can't afford to buy it already built, so "implementation" for him is "assembly" for us
as in "some assembly required"
the "design" being the bbastro one (or something yet to be designed/implemented)
cradek: yes probably
good morning skunkworks
good morning jepler.
How is everything going? keeping busy?
we finally got rain here. Good inch or so - we really needed it.
oh not bad
work is alternating between "get those bugs fixed" and "for god's sake, don't change anything, you'll introduce a bug" .. today is a "for god's sake" day
we could use the rain too but it's not coming
We get we are changing the proccess... Need it done by yesterday.
'we are changing the process'
although my programmer had a laugh this week when he created a bit that would tell if a certain form was open. telephone purchase order. blnTelePOOpen
(it doesn't take much for us I guess)
don't put me in the POO pen !!
(purchase order open?)
hi SWPadnos !
looking at your earlier question