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Poor man's DAS

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nuckollsr(at)cox.net
Guest

Posted: Wed Feb 14, 2007 7:33 am Post subject: Poor man's DAS

I can't recall if I've mentioned this company before here

on the list but for those interested in watching, gathering,

storing and plotting various data from their airplane or

elsewhere, take a look at this product:



http://www.labjack.com/labjack_u3.php?prodId 5



I've had one on the shelf for about a year but didn't

have the incentive (work order) to get it out of the box

and see what it takes to make it sing, dance and do dishes.



Got a task coming up for a customer that can use a small

portion of its features so I got it out and fired it up

last night. It's almost TOO capable . . . takes awhile to

wade through all the "mommy, mommy, look what I can do!!!"

things to get it running with a simple task: read and

store 3 channels of analog data.



But the more I play with it, the more impressed I am with

the capability it offers for a paulty $100.



One OBAM aviation task I'm considering for it is to measure

and store voltage and current values for a battery recharge

cycle using the various $low$ charger/maintainers. It's

pretty easy to look at a recharge voltage curve and assume

that the last 10% of the time under the curve accounts for

10% of total energy transfer. However, we know that's not

the case.



What the voltage curves don't show us is that during the final

phase of the upward climb for applied voltage, current going

into the battery is going down, hence the last 10% of charge

time may account for only a small percentage of total energy

transferred to the battery. It would be cool to really go

measure that.



So as soon as my customer takes the hit on my exorbitant

fees to learn how to use this thing do to his job, I'll be

able to move the equipment over to the bench where the battery

tests are going on for some elightening 'fun' stuff.



The second battery recharge using a Battery Tender completed

this morning. The attached image shows the first and second

recharge voltage curves. The first curve is in red, the second

in black. I note that this charge cycle ended earlier (battery

wearing out? It's several years old) but the charge cycle extended

into the end-of-charge voltage inflection. Given that devices

like the Battery Tender probably use analog comparators to

sense when states change, the earlier curve may have terminated

a tad early on noise . . . nonetheless, it appears that these

whimpy little 'chargers' may be quite capable of stuffing all

the snort back into an SVLA battery . . . all it takes is patience.



Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

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pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Wed Feb 14, 2007 8:56 am Post subject: Poor man's DAS

Thanks a bunch for the link, I've seen similar devices in my engineering

publications, but all were priced at least 3 times higher. This is

definitely going to find it's way into my bench. Way-cool! The support files

and operating system compatibility files are impressive to say the least.

Thanks again, this is a real gem of an instrument!

Craig Smith

Do Not Archive

--

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

frank.hinde(at)hp.com
Guest

Posted: Wed Feb 14, 2007 9:03 am Post subject: Poor man's DAS

Hey Bob,



Glad to see the Battery tender junior re-gets your

endorsement...Especially as I'd just bought one.



This device looks pretty useful, I could imagine using it in flight to

gather all sorts of data or to compare to a suspect engine monitoring

system for example.



The only issue I see is the analogue inputs are not rated up to 14v (10v

was the max) but somehow you have been measuring the full charging

voltage...How did you do that?



Speak slowly...Im a Mechanical engineer...



Frank 



 



--

fvalarm(at)rapidnet.net
Guest

Posted: Wed Feb 14, 2007 1:31 pm Post subject: Poor man's DAS

Bob,



I'm interested in this Labjack too for a different application.  My question

is, does it come with software that is loaded on a PC to control the

labjack?  If not, what software does one use or does one have to write their

own from scratch?



Bevan 



--

nuckollsr(at)cox.net
Guest

Posted: Wed Feb 14, 2007 2:29 pm Post subject: Poor man's DAS

At 01:30 PM 2/14/2007 -0800, you wrote:



 	  Quote: 	
		  



Bob,



I'm interested in this Labjack too for a different application.  My question

is, does it come with software that is loaded on a PC to control the

labjack?  If not, what software does one use or does one have to write their

own from scratch?



Bevan


	


   It comes with a manually operated test program that lets you

   individually wiggle any i/o port and make measurements. Really

   handy for setting up or troubleshooting. It also comes with a

   scaled down version of DAQFactory, the "express" version that

   lets you set up DAS and control routines and capture/plot data.



   I have the test tools up and running. I hope to get into the

   DAS application this weekend. You can also write routines

   to access the Labjack from a variety of applications such

   as LabView and Visual Basic.



   Bob . . .

klehman(at)albedo.net
Guest

Posted: Wed Feb 14, 2007 4:48 pm Post subject: Poor man's DAS

Isn't the real value of an intelligent charger simply that it prevents 

or limits overcharging and battery damage?   I suspect that any charging 

scheme that prevents overcharging is 99% of the answer regardless of the 

exact programming algorithm. A wall wart and an LM317 voltage regulator 

set for float voltage for example has worked well for me for many years. 

Since the current at float voltage (self discharge current) seems to end 

up the same, I'm confident that the slow charge is fully charging the 

battery and that I'm not overcharging. As noted , limiting the voltage 

really only slows the last few percent of charging.



I've been playing a bit with desulphating pulse charging. It hasn't 

helped badly sulphated batteries for me so I've been sceptical. However 

lately I've been using a 60 hz 40 volt square wave (discharging a 

capacitor) to periodically top up seldom used batteries (non aviation) 

and I think it might be improving the cranking current that I can get 

out of them and extending their lives at least a bit. Might be neat to 

try to generate some hard numbers for that.



Ken



 	  Quote: 	
		   snip

 . . . nonetheless, it appears that these

 whimpy little 'chargers' may be quite capable of stuffing all

 the snort back into an SVLA battery . . . all it takes is patience.



 Bob . . .



 ------------------------------------------------------------------------

nuckollsr(at)cox.net
Guest

Posted: Wed Feb 14, 2007 6:36 pm Post subject: Poor man's DAS

At 07:50 PM 2/14/2007 -0500, you wrote:



 	  Quote: 	
		  



  Isn't the real value of an intelligent charger simply that it prevents 

 or limits overcharging and battery damage?   I suspect that any charging 

 scheme that prevents overcharging is 99% of the answer regardless of the 

 exact programming algorithm. A wall wart and an LM317 voltage regulator 

 set for float voltage for example has worked well for me for many years.


	


    Yes . . . for sustaining a battery in storage, you support

    the battery at or slightly above the stable open circuit

    terminal voltage which is on the order of 12.9 to 13.0 volts

    at room temperature. To fully charge a battery at room temperature,

    13.8 volts will eventually do it but to speed things up toward

    the end a shutoff/top-off of 14.0 to 15.0 volts is not uncommon

    for smart chargers.



 	  Quote: 	
		    Since the current at float voltage (self discharge current) seems to end 

 up the same, I'm confident that the slow charge is fully charging the 

 battery and that I'm not overcharging. As noted , limiting the voltage 

 really only slows the last few percent of charging.


	


    Well, I can try it out and see. On one of the recharge cycles

    I'll set it up on a constant current power supply limited

    at 13.0 volts and see what kind of energy the battery accepts.



 	  Quote: 	
		  I've been playing a bit with desulphating pulse charging. It hasn't helped 

badly sulphated batteries for me so I've been sceptical. However lately 

I've been using a 60 hz 40 volt square wave (discharging a capacitor) to 

periodically top up seldom used batteries (non aviation) and I think it 

might be improving the cranking current that I can get out of them and 

extending their lives at least a bit. Might be neat to try to generate 

some hard numbers for that.


	


    Just had a direct e-mail question from a reader:



"Comments/Questions: Hi Bob. I took your class several years ago in 

Watsonville, CA and I thought you might have the answer for me. I am 

wondering how often my battery should be changed out. It is a Concorde 

RG-35AXC battery and it was placed in service "new" in October of 2002. 

This battery is in a C-182. It flies approximately 100 hours per year. I 

have noticed the battery not cranking the O-470 as strong as it did 6 

months ago. I am just wondering what the expected life service for a 

battery of this type is. Thanks for your help!"



    To which I answered: There is no really hard data on "expected" service

    life of a battery. There are huge variables not the least of which include

    how many times it has been fully depleted and how long it was allowed

    to sit in a discharged state. I'll suggest that if the battery is 

noticeably

    soft while cranking an engine, it has probably been unserviceable as a

    standby source of energy for a long time.



    Replacement of batteries should be based on energy available

    to run endurance mode goodies for what ever length of

    time you choose. The FAA is fond of "30 minutes". I'm fond

    of "Duration of Fuel Aboard". Which ever you choose, if you

    periodically test the battery for its ability to meet your

    endurance goals, you'll find that it gets replaced long before

    it won't crank the engine any more.



    And again, "service life", whether based on engine cranking

    ability or demonstrated endurance performance can be influenced

    strongly by the environment in which the battery lives. I'd

    be hard pressed to either persuade or dissuade you from

    believing that your October 2002 purchase was not a good

    value.



    -----------------



    There are a number of products that tout some ability

    to reverse sulfation. The problem is that the techniques

    range from simply "pulse charging" to finely tuned pulses

    of energy that supposedly match the natural resonant

    frequency of the sulfate molecule . . . 3.26 Mhz as I

    recall. Current levels for suggested pulses range from

    hundreds of milliamps to as much as 20 amps or more.



    Do a Goggle on "desulphation" and "dsulfation" and

    you'll get a total of 69,000 hits the vast majority

    of which discuss some process touted to rejuvenate

    a sulfate-distressed battery. Even our friend Jim Weir

    published an article in April 2002 Kitplanes that

    suggested some popular flavor of battery performance

    booster.



    The wild variability of processes and techniques offered

    in the marketplace suggests that nobody has hit upon

    the one true process. Some guy from Soneil in Canada

    sent me some chargers that featured "battery

    desulfating" capabilty. I've studied both a 14v and

    28v version on a DAS and 'scope and as near as I can

    tell, they perform just like a Schumacher "smart

    charger" . . . I can detect no special energy output

    that might target the evil sulfate crystals.



    I'll suggest that parking the airplane on a maintainer

    and doing cap checks at one year and every 6 months

    thereafter will yield the ideal replacement interval

    for any given battery. If your endurance criteria is

    zero minutes, then run it until it won't crank the

    engine any more. Further, it's a sure bet that your

    perceived service life will exceed that of the guy

    in the next hangar that wants 3 hours of support for

    the e-bus.



    I just stuck a discharged SVLA battery on the 13.0 volt

    power supply. We'll see what the battery will suck up

    at that voltage.



     Bob . . .

lumkes(at)msoe.edu
Guest

Posted: Thu Feb 15, 2007 12:14 pm Post subject: Poor man's DAS

I can personally  vouch for the Labjack series. I have purchased and installed approximately 25  units in a teaching laboratory; no matter how many mistakes the student made,  only one unit ever failed and the factory replaced it at no charge. I now use  them again at my "new" position, and have my own personal one at home. I have  used it to record data around the house (temp's, flow, etc.) and plan on  installing one in the airplane with a mini-ITX PC to have my own data logger /  EIS. The interface can easily be done in Labview, and having the "carpc" will  also allow me to run PocketFMS on a split screen. This is definitely  "experimental" and so all required gauges will also be "steam wired". There so  many ICs now like thermocouple amplifiers with built in cold junctions, small  economical pressure transducers, etc., that adding features are easier now than  ever before for amateur electrical system integrators (like  myself).

  

 Long term plans:  adding solid state gyros (IC chips now have this ability) for AHRS and wing  leveling / GPS based auto-pilot.

  

 John

    [quote][b]

khorton01(at)rogers.com
Guest

Posted: Thu Feb 15, 2007 4:51 pm Post subject: Poor man's DAS

On 15 Feb 2007, at 15:11, John and Kim Lumkes wrote:



 	  Quote: 	
		   I can personally vouch for the Labjack series. I have purchased and  

 installed approximately 25 units in a teaching laboratory; no  

 matter how many mistakes the student made, only one unit ever  

 failed and the factory replaced it at no charge. I now use them  

 again at my "new" position, and have my own personal one at home. I  

 have used it to record data around the house (temp's, flow, etc.)  

 and plan on installing one in the airplane with a mini-ITX PC to  

 have my own data logger / EIS. The interface can easily be done in  

 Labview, and having the "carpc" will also allow me to run PocketFMS  

 on a split screen. This is definitely "experimental" and so all  

 required gauges will also be "steam wired". There so many ICs now  

 like thermocouple amplifiers with built in cold junctions, small  

 economical pressure transducers, etc., that adding features are  

 easier now than ever before for amateur electrical system  

 integrators (like myself).


	


Bob and John,



Thank you very much for the recommendation for the Labjack.  This  

unit should allow me to add some missing items to my flight test data.



John - where do you purchase suitable, affordable, robust  

transducers?  I'm looking to measure some temperatures, and flight  

control positions.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

do not archive

lumkes(at)msoe.edu
Guest

Posted: Fri Feb 16, 2007 6:21 am Post subject: Poor man's DAS

Kevin,



High Temps: Standard thermocouples with a an Analog Device AD594 or similar 

Low Temps: many options, I use a LM34, outputs degrees F in mV with a 5V

supply Cheap 

Low precision distance: Sharp IR GP2D120 

Low pressures: check Jameco or similar, search Keywords for pressure sensor;

they have several Motorola Freescale 0-1.45psi for 8-14 dollars.



You can directly measure a thermocouple output with a good 16bit A/D

converter; probably not directly with the labjack. 



This is only a small sampling of the exploding field of "cheap" electronics,

very capable linear IC circuits, and little programmable controllers. 



Bob and John,



Thank you very much for the recommendation for the Labjack. This unit should

allow me to add some missing items to my flight test data.



John - where do you purchase suitable, affordable, robust transducers? I'm

looking to measure some temperatures, and flight control positions.



Kevin Horton RV-8 (finishing kit)



Ottawa, Canada

nuckollsr(at)cox.net
Guest

Posted: Fri Feb 16, 2007 6:41 am Post subject: Poor man's DAS

At 07:49 PM 2/15/2007 -0500, you wrote:



 	  Quote: 	
		  



Bob and John,



Thank you very much for the recommendation for the Labjack.  This

unit should allow me to add some missing items to my flight test data.



John - where do you purchase suitable, affordable, robust

transducers?  I'm looking to measure some temperatures, and flight

control positions.


	


   For temperatures up to 150C consider the LM135 series devices

   by National. These are voltage sensitive zeners with a

   regulation voltage of 10mv/degree-K. You can bias these little

   fellers up with a single resistor pull-up to 5v. The measured

   voltage at 25C is (273+25)x10 = 2.980 volts.



   For higher temperatures, my favorite jelly-bean is the AD596/597

   series thermocouple to 10mv/degree-C converter chips.



   For control positions, consider "string pots" or "draw string pots".

   These are spring loaded drums of fine cable mounted on

   a potentiometer. See:



http://www.dataq.com/support/documentation/pdf/article_pdfs/stringpotan.pdf



http://www.aeroelectric.com/Pictures/Data_Acquisition/String-Pot.jpg



   Here's one I made using a piece of retraction spring from a

   pocket tape measure, a miniature RV-4 series potentiometer

   and some odd bits of aluminum stock.  The "cable" is 7-strand

   u-control flying wire from a hobby shop.



   This was used to measure a stroke of about 1/2" on the

   master brake cylinders of a cockpit simulator. You can

   measure longer strokes by using multi-turn pots. The metal

   work is pretty straightforward. These can be had as purchased

   items. See:



http://www.globalspec.com/FeaturedProducts/Detail/celesco/Compact_String_Pot_SP1/29565/0?fromSpotlight=1



http://www.unimeasure.com/



http://www.impresssensors.co.uk/draw-wire.htm



   They're not inexpensive.



   Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

ainut(at)hiwaay.net
Guest

Posted: Thu Feb 22, 2007 7:20 am Post subject: Poor man's DAS

John, my plans are similar to yours. Good luck with  them.

  

 I've had a labjack U12 for many years now and may have  found a better alternative.  Go to some of the Freescale (Motorola)  processor seminars where the price includes a test board.  You're more into  the design phase during implementation but you can keep costs in the under $10  range if you like.  The downside is that even though CodeWarrior lite comes  'free' during the seminar,it is ATROCIOUS as a development  environment.

  

 David M.

  

 [quote]   ---

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