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'[EE]:: ECAN data logger ideas sought'
2008\11\11@041443 by apptech

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Before I consider finally building the low cost universal "extra cheap and
nasty" generic data logger that I keep intending to build for general
purpose personal use, but somehow never get around to, what products have
people here developed, what do they do, and what cost are they available
for?. Desireable logging capability is analog voltage (probably about 10
bits). Ideal interface is USB download. Ideal memory is changeable SD card
(could make USB or any interface unneeded** ). Analog and digital outputs a
bonus (and would only make sense if there was a direct PC
connection/collection mode).

Over the years I've built numerous things which "logged data" but never a
"data logger" per se.
Every time I have the need for such a device I realise yet again how nice it
would be to have a universal recorder/logger/ ... but so far the immediate
need has resulted in a custom solution or manual measurement or whatever. It
would be nice to have a handful of loggers available that could be used for
a wide range of purposes. Typically the ability to substitute for a
voltmeter or ammeter would be useful. The ability to float inputs would be
valuable, but using two or more loggers for this would suffice if they were
cheap enough and could be properly time synced to allow data combining. Raw
download of data to an easily accessible file is essential but any added gee
whizz analysis features may be useful. Features like bridge conditioning,
instrumentation amp front end etc would be useful, but probably indicates a
product well upmarket from what I had in mind*.

There are of cours also various commercial units available and people may
have wish to recommend some cheap and useful favourites.

A suitably priced or capable measurement frontend may be worth considering
if the price was right. eg lo\ike the PICO products but preferable with a
(much) smaller ratio between the cost of the end product and the IC's they
use. Dataq, ... ?

Yes, I can easily enough troll the web for promising examples (and even ebay
has a few good examples sprinkled amongsth the 95% of "data loggers" there
which are GPS recorders.)

But YOU are more likely to have just what I'm looking for. So, who are you,
and what is it that you've got?

If nobody has a good cheap and available solution, what do you want my
device to do, how much will you pay and how many do you want? :-)


  Russell McMahon

* Sample example: A solar panel charges a battery by day which runs a light
by night. Log at 1 second intervals (or 10) Vpanel, Ipanel, I battery,
Vbattery (I's and V's may well not be the same for "technical reasons"), I
load, V load, temperature, ... .

Some of these measurements may not be ground referenced (although in this
case all could be made to be). Temperature could be RT100, thermistor V, ...
.

** In an ECAN device the ability to write to a removeable SD card could lead
to an extremely low cost solution. It may come down to whether an SD card
socket or a USB plug is cheaper :-).



2008\11\11@073928 by olin piclist

face picon face
apptech wrote:
> Over the years I've built numerous things which "logged data" but
> never a "data logger" per se.

I've built a number of data loggers too, each specific to its project.  I've
occasionally thought a general purpose data logger too, but reached the
conclusion that there are way too many variables to make something both
tractable and general purpose enough to be useful in more than just a few
niches.

For example, how fast does it need to be?  Some projects would require audio
frequencies and beyond, and 10 bits might be good enough.  That could be
handled by real time streaming over USB.  Some projects require something
more like a logic analyser where speed and number of channels is important.
There you probably need local high speed memory and a way to dump it later.
Some project may only need a few seconds of such sampling while others may
need to log data for days or weeks or months.  There is very little common
ground.

A recent project I did needed very high resolution analog measurements but
only every 25mS.  For that I slapped two sigma-delta A/Ds on a ReadyBoard-02
and sent data back over USB in real time.

A while ago we needed 24 channels of 10 bit analog at 100Hz sample rate in a
portable box out in a field (literally).  That was done with battery backed
RAM and three boards each handling 8 channels.

The conflicting requirements go on and on.  I've come to the conclusion that
it's easier to slap together what you need at the time than to try and guess
what you might need next.  I've done custom data loggers twice in the last
few months alone.  One I describe above.  The other interpreted digital data
over a custom protocol and sent this back to the host in real time via USB.
It's hard to imagine a small and cheap enough general purpose product that
would serve both needs well.

So here is my suggestion (totally unbiased, of course ;-) ).  Keep a pile of
ReadyBoard-02 on hand and slap on whatever unique data gathering hardware
you need for the task at hand.  Seriously, we have used ReadyBoards a number
of times for exactly this purpose ourselves.  They really are handy for this
sort of thing.  It would take a large number of projects to equal the work
of putting together one general purpose data logger, if you could ever agree
on the definition of one.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\11\11@132121 by Alan B. Pearce

face picon face
>Before I consider finally building the low cost universal "extra
>cheap and nasty" generic data logger that I keep intending to
>build for general purpose personal use, but somehow never get
>around to, what products have people here developed, what do
>they do, and what cost are they available for?. Desireable logging
>capability is analog voltage (probably about 10 bits). Ideal
>interface is USB download. Ideal memory is changeable SD card
>(could make USB or any interface unneeded** ).

If you don't want to go Olins way and build something yourself, Yokogawa
make a datalogger that is like an electronic pen plotter, but with more than
the usual 4 or so pens. I don't know what the maximum data rate would be,
but it does have all sorts of storage capability (the thing is effectively a
dedicated PC, I believe), and can have network connection or removable
storage plugged in.

IIRC it can also act as a pre-amp for low level signals and feed them out
BNC connectors for remote access as well, but my memory is getting hazy on
that bit.

Sorry cannot remember the model number, but the price was something in the
GBP7-8k as I remember it.

2008\11\11@135935 by M. Adam Davis

face picon face
I don't think you've sufficiently defined your requirements.  ;-D

So far you've only said you need the following features:
- Cheap
- Nasty
- 10 bit A/D, voltage and current ( speed???)
- USB download (USB live needed as well?)
- SD memory (FAT12, FAT32? New 2+GB cards? Fast 4 bit interface, or slow SPI?)
- Analog output (voltage, current, range, resolution, precision...?)
- Digitial output (inputs too?)
- Isolated inputs (and outputs?)
- Clock synchronization (time sync as well, or just a sync pulse from
a 'master'?)
- Raw download to a file (CSV, binary, XLS, PDF, flash, EXE...?)
- Programmable gain amp?
- Instrumentation amp?
- Bridge conditioning/power/amp?

Things you've hinted at are:
- Log serial streams (SPI, I2C, RS-232, RS-485, CAN)
- Knowledge of frequently used protocols (GPS/NMEA, automotive diagnostics?)
- Manual measurement (display, user interface?)

What about power requirements?  Temperature, environmental?  Powering
sensors? Arbitrary waveform generator?

But the real problem is not getting the hardware to do all this.

The real problem is writing software (and a user interface) that is
flexible enough to be able to do your solar example below, and,
without changing the hardware, move into an application that requires
higher speed analog recording (audio, accelerometer, etc) for 3
seconds before and after a trigger pulse on a digital input.

I see a few interesting possibilities:
- really, really cheap hardware with a USB bootloader - a complex
program on the PC that writes custom firmware for a particular
datalogging app.  each time you need a different type of logger,
extend the PC program to provide an interface for and produce new code
that's loaded on the datalogger.  Having a website that allows you to
make a "strategy (which is just the firmware)" online and download it
to the datalogger provide an interesting business opportunity.
- A datalogger with enough power to run a scripted language (python,
lua, etc) and script up your datalogger by hand.  With PIC32, USB otg,
and a cheap display you might be able to plug in a keyboard and script
it on the device on location, no PC needed.

I would start very small with an almost trivial logger and a very
powerful processor on a PCB with lots of prototyping area, a wide
range input power supply, and basic protection on the inputs.  Then
spend the rest of your time on the software, because that's what will
make the datalogger useful or not.

One thing I'd like to add to the above list is that the datalogger
itself look like a USB drive.  Then you can upload firmware files
(it'll reflash itself when it sees such a file on bootup), scripts,
and download data as files.

-Adam


On Tue, Nov 11, 2008 at 4:14 AM, apptech <spam_OUTapptechTakeThisOuTspamparadise.net.nz> wrote:
{Quote hidden}

> -

2008\11\11@222927 by Xiaofan Chen

face picon face
On Wed, Nov 12, 2008 at 2:20 AM, Alan B. Pearce
<.....Alan.B.PearceKILLspamspam@spam@stfc.ac.uk> wrote:
> If you don't want to go Olins way and build something yourself, Yokogawa
> make a datalogger that is like an electronic pen plotter, but with more than
> the usual 4 or so pens. I don't know what the maximum data rate would be,
> but it does have all sorts of storage capability (the thing is effectively a
> dedicated PC, I believe), and can have network connection or removable
> storage plugged in.
>
> IIRC it can also act as a pre-amp for low level signals and feed them out
> BNC connectors for remote access as well, but my memory is getting hazy on
> that bit.
>
> Sorry cannot remember the model number, but the price was something in the
> GBP7-8k as I remember it.

That is rather expensive compared to Agilent 34970A (34980A is even more
powerful). In the previous job, I bought three 34970A for the R+D
department and we all liked it very much. In the current job, we bought
two 34980As for the temperature measurement.

Xiaofan

2008\11\12@070411 by Michael Rigby-Jones

picon face


> -----Original Message-----
> From: piclist-bouncesspamKILLspammit.edu [.....piclist-bouncesKILLspamspam.....mit.edu] On
Behalf
> Of Xiaofan Chen
> Sent: 12 November 2008 03:29
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE]:: ECAN data logger ideas sought
>
>
> That is rather expensive compared to Agilent 34970A (34980A is even
more
> powerful). In the previous job, I bought three 34970A for the R+D
> department and we all liked it very much. In the current job, we
bought
> two 34980As for the temperature measurement.

We use a lot of 34980A for production test, they are very good
instruments.

Regards

Mike

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