Go Back   EcoModder Forum > EcoModding > Instrumentation
Register Now
 Register Now
 


Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-11-2008, 11:04 PM   #1 (permalink)
EcoModding Lurker
 
Join Date: Nov 2008
Location: oswego, ny
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
USB Voltmeter?

Hey,
New to the board, as recommended by a user here. I currently just accepted a project to create a GUI to monitor two things: voltage across twelve batteries of an electric car, and to monitor the overall voltage of an electric car. Ideally, I want to create a Java GUI that reads an input from several voltmeters. Any suggestions?

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-12-2008, 12:00 AM   #2 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,827

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 53.56 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 61.46 mpg (US)
Thanks: 3,529
Thanked 6,323 Times in 3,270 Posts
The Arduino platform can be set up as a multiple battery voltmeter, and it can spit out its data stream via USB. Not sure if that's what you're after though. (There are probably better solutions, but when the only tool you have is a hammer....)
__________________
Latest mods: 3-cylinder Mitsubishi Mirage. EcoMods now in progress...
Ecodriving test:
Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 11-12-2008, 12:50 AM   #3 (permalink)
EcoModding Lurker
 
Join Date: Nov 2008
Location: oswego, ny
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Can I monitor each battery independently? I need to monitor a minimum of twelve batteries, and the whole circuit (13), and it would be a plus if I could monitor two auxiliary batters. It's for a research project, so money isn't much of a factor. Grants will (hopefully) be paying for it.
  Reply With Quote
Old 11-12-2008, 03:06 AM   #4 (permalink)
SuperMID designer
 
Yoshi's Avatar
 
Join Date: Mar 2008
Location: Yokohama, JAPAN
Posts: 37
Thanks: 0
Thanked 13 Times in 2 Posts
The Arduino platform has six analog inputs, 0 to 5V range from ground.
You need voltage dividers for above 5V measuring, and three Avrduino's will have up to 18 analog input.

Commercial products look very expensive, such as following for 8 channel.
8 Channel Voltage Data Logger

Ken@Japan
  Reply With Quote
Old 11-12-2008, 06:37 AM   #5 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location:
Posts: 5,038

pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
90 day: 53.56 mpg (US)
Thanks: 158
Thanked 267 Times in 210 Posts
You can also use something like a 4051 to "multiplex" your analog inputs. They can turn one analog pin into 8:
Arduino playground - 4051

They are like $0.47 from mouser. And you have 6 analog pins on the typical arduino. So you will want a couple 4051s.

HCF4051BEY

If your usb can power the voltage monitor, I would say get an iDuino kit for $18. iDuino : Fundamental Logic WebStore, Electronic Kits and Components

so with one *duino and two 4051s (and a bunch of carefully selected resistors) you should be able to build something that can monitor up to 20 voltages
and send a data stream to a laptop, for about $25 all told.

One of the tricks here is that voltage is measured to ground, and you have to select different voltage dividers for each battery connection as you want to limit the voltage to max 5 volts per probe.

I would also suggest using old phone/network cable for the hookup to the batteries.
__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Old 11-12-2008, 01:39 PM   #6 (permalink)
Master EcoModder
 
Join Date: Jun 2008
Location: London, Ontario
Posts: 1,096

2k2Prot5 - '02 Mazda Protege5
90 day: 33.82 mpg (US)
Thanks: 0
Thanked 12 Times in 9 Posts
Something simple like an iDuino with USB support is a good plan, but i would recommend sourcing an ADC that can handle higher voltage. Voltage dividers = leakage current, and referencing to ground is not really an option, you want to reference across the battery. Granted, you can reference each node of the network of battereis to ground and do the math, but you're better off with two wires per battery leading to an adc that can handle it. They, too would be cheap. Check out Digi-Key Corporation - USA Home Page
  Reply With Quote
Old 11-12-2008, 02:33 PM   #7 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location:
Posts: 5,038

pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
90 day: 53.56 mpg (US)
Thanks: 158
Thanked 267 Times in 210 Posts
Quote:
Originally Posted by MazdaMatt View Post
but you're better off with two wires per battery leading to an adc that can handle it.
Sorry to bust your chops here matt, but you have not given any specifics (i.e. a chip #). I don't know how one can make an assertion about betterness without discussing the specifics here.

I would agree it is another option, at best, but would probably be more work due to lack of previous arduino examples and lack of specifics from its suggester.

the divider leakage current can be accomodated with large resistors and a common ground under cpu control if sleep mode is desired.

Did you have a specific ADC in mind? What is it's leakage current and how much support circuitry does it need, and do you have to buy one for every battery, and is there prior open source work that the OP can build off of (schematics, code, etc)?
__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Old 11-12-2008, 02:47 PM   #8 (permalink)
Master EcoModder
 
Join Date: Jun 2008
Location: London, Ontario
Posts: 1,096

2k2Prot5 - '02 Mazda Protege5
90 day: 33.82 mpg (US)
Thanks: 0
Thanked 12 Times in 9 Posts
Wow, i just got seriously chewed out for some suggestions...

OP didn't say he was incapable of working with electronics and he didn't say he wanted an open source option. I work with this stuff every day and that's what I would have said to someone in a meeting room if they asked the same question. If he wants details and likes where i'm going, then he can ask me another question.

No, i did not select specific part numbers for him because I assumed that he was capable of doing so using the very simple parametric search on digi key. I don't know what his system voltage is, what the processor voltage is, what the space constraints and budget are, if he is capable of using SMT, what busses he may have available, etc.

I don't like voltage dividers because of the leakage current as well as the tuning required for every single one due to resistor tolerance, and I like the idea of 2 wires per battery so that he is always reading in the same range of voltage (which allows selection of an ADC best suited to that voltage range). One wire at each battery would mean that he is measuring 12v at the first one, 24 at the second, 36, 48, etc. This requires a variety of ADC's. There MAY also be complications to connecting the pc ground to the car ground, which are avoided with 2-wire. I currently have two projects on the go that are acting little sketchy because the customers are connecting my digital grounds to their pc and analog grounds.
  Reply With Quote
Old 11-12-2008, 03:19 PM   #9 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location:
Posts: 5,038

pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
90 day: 53.56 mpg (US)
Thanks: 158
Thanked 267 Times in 210 Posts
Quote:
Originally Posted by MazdaMatt View Post
Wow, i just got seriously chewed out for some suggestions...
You were being presumptuous. You said your solution was better but refuse to back it up with a specific example. All you have to do to back it up is cough up a schematic and some part numbers.

My guess is that it will be, and I've been wrong before:
more complicated
more costly
more difficult to implement

and there's no way to tell if it will leak enough less to matter, if indeed it does leak less (need to look at the adc datasheet).

So can you please produce a schematic for my edification?
__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Old 11-12-2008, 03:22 PM   #10 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location:
Posts: 5,038

pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
90 day: 53.56 mpg (US)
Thanks: 158
Thanked 267 Times in 210 Posts
It is worth noting that if you get a 0 volt battery, then you will get some strange readings from the other batteries if you have to "do the math"

__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tips for USB datalogging out of an iDuino? jim-frank Instrumentation 6 11-12-2008 07:55 PM
USB connected LCD? SVOboy OpenGauge / MPGuino FE computer 3 09-15-2008 08:54 AM
OBD2 - USB on ebay --- any good? Noel Instrumentation 7 08-21-2008 12:15 AM
Cheapy USB Serial OBDII Ebay Purchase Help Nerys Instrumentation 2 06-02-2008 02:23 AM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com