Anybody made logging osciloscope/voltmeter out of a PC?

[tomv]

Hello Guys!

Could you share how you measure/test/log data about your motors and especially batteries? I'm using watts-up on the bike and voltmeter at home and find this seriously insufficient. What do people use to make those discharge charts for batteries? Ideally I'd love a gadget that logs say a dozen streams of voltages/currents/resistances (for temp measurement) to my PC where I can plot/analyze that.

I'm thinking of the following option:

- Use PC audio card with lots of inputs. There are USB external cards with say 8 inputs. Hook up those to resistors and all done. This in principle could do everything needed, but with lots of work in hooking up the thing. Any mistake in wiring would most likely cook the card and maybe PC

- Buy logging multimeter or digital oscilloscope. Disadvantages: lots of $$$$ needed. Still only can only measure one or two things at a time. Would like to measure lots of things at a time.

Any other ideas? There are PC data acquisition boards but again, even more $$$$. Looks like focus is on precision/high-frequency rather than on low cost and many streams of data.

I'm also thinking that a cheap power supply + PC analog outputs + couple of components could be combined to make a very flexible programmable charger for any chemistry (not very efficient, more for testing).

Thanks for any ideas!

 

[tomv]

Bellow are a few things I found. Each of them would be nice, other than the price (and usually few input channels).

Agilent, 32 inputs/32 outputs, USB connection, $420
http://www.home.agilent.com/agilent/product.jspx?nid=-35071.739737.00&cc=US&lc=eng

Pico-Scope:
Convenient, 0-20V input range, low precision, 1 or 2 channel, $250+
http://www.picotech.com/oscilloscope-specifications.html

Bit-Scope
Similar to Pico, $500+
http://www.bitscope.net/store/?p=list&i=cat+scope

Also an update on sound-card based scopes. Not too good for battery analyzing - soundcards apparently filter out their inputs for everything bellow 20Hz

 

[monster]

in maplin you can get an experiment board that runs USB. its $50 and can measure 2 signals up to 5v. http://www.maplin.co.uk/Search.aspx?criteria=experiment board&source=15&SD=Y
it comes with software

just got to figure out how to turn voltage and current info into a 0-5v reading. i saw a clamp meter somewhere that had mV outputs to a multimeter that you could use for current, but it was about $140. maybe a DC-DC converter for the voltage input?

 

[monster]

EagleTreeSystems' MicroPower E-Logger has been mentioned before on this site.
http://www.eagletreesystems.com/MicroPower/micro.htm

im interested in this thread because i will have to set up a data logging system soon and i want to do a cheap one for my bike too.

 

[tomv]

Thanks for the links! Both of those things are very neat. Getting signal into 0-5V is easy if you know the range of signal you'll measure. Voltage can be brought down with voltage divider (Vout = Vin * R1/(R1+R2)) and current via shunt resistor. This is basically a part of simple multimeters, so I'm thinking to gut some cheap analog $10 multimeter to get normalized signal that can be fed into USB DAC. Still only one channel per multimeter, but better than arranging resistors for every measurment.

That eagletree thingy is really nice. I wish I knew about it before i bought my non-logging watts-up. But it would not work as a general logging tool - I suspect resolution is horrible . Say if it measures 70V +/- 0.5% (they don't say their precision, so I'm guessing) it would be useless in logging LiIOn battery charger/balancer..

Another dream gadget that's pricey ($350). 8 input channels, 2 output, 12 bit resulution, software selectable gain (up to 10V), usb is isolated from input signals, so won't fry your PC.

http://www.keithley.com/products/dataacqmodules/?mn=KUSB-3100

Or alternatively even more powerful PCI card ($250). 16 in/16 out, up to 60V
http://www.keithley.com/products/dataacqmodules/?mn=KPCI-PDISO8A

 

[tomv]

Looks like this could be a winner. If it does what I think it does I'll get a couple
http://www.labjack.com/labjack_u12.php?prodId=27

- 8 inputs, 12 bit. Programmable gain +/- 10V
- 1200 samples per second. That would be plenty
- Tiny and no power supply needed
- Can plug in a bunch of them into single USB!

I'm just thinking of the ways to use it. How about PDA and some sensors to show:
- Battery voltage/amps/watts/wh used/wh remaining/temperature
- Motor rpm (speed), temperature
- Strain gouge on pedals to measure "human" motor.
- Hook outputs to relay to have Low voltage/High voltage/High current/Over temperature cutoff
- Write software to limit power/speed/power at low speed (inefficient)
- Wind speed indicator for true speed measurement.
- Use data to analyze battery capacity, motor efficiency at any speed/aerodynamic drag or to find out which of your legs is stronger!

Use it with dumb power supply and and relay to create a multi chemistry charger (SLA/Nimh/Lion/A123)/battery analyzer.

Hook it up to each cell in a pack separately (may need a couple) and see how well your cells are matched/balanced.

Anybody actually used this or something like it?

 

[Jeremy Harris]

I use a USB Instruments datalogger/scope. It is easy to use and works well, although only has a couple of channels. The website is here: http://www.usb-instruments.com/oscillo_stingray.html

The software works well even on a low performance laptop. I did some logging of chain frequency data last weekend using it on an Asus Eee sub-notebook, and it worked fine.

Jeremy

 

[monster]

ok so i bought the velleman vm110 from maplin today. the bad thing is they seem to expect you to know program languages so you can write your own programs.

i just want to data log stuff, i dont want to learn to program

 

[rkosiorek]

i looked at the VM110 for an engine dyno project. instead i decided to buy the Velleman PCS10 4 port data logger. it comes with a software package called PC-LAB 2000 that will log 4 channels of data and display them on screen in real time. 4 channels is more than i need for the dyno.

though i am capable of writing the software i decided my time was better spent elsewhere. the PCS10 works so well that i am considering buying one of the Velleman oscilloscope kits for other projects.

rick

 

[monster]

i looked at the VM110 for an engine dyno project. instead i decided to buy the Velleman PCS10 4 port data logger. it comes with a software package called PC-LAB 2000 that will log 4 channels of data and display them on screen in real time. 4 channels is more than i need for the dyno.

though i am capable of writing the software i decided my time was better spent elsewhere. the PCS10 works so well that i am considering buying one of the Velleman oscilloscope kits for other projects.

rick

nice one rkosiorek i'll get the PCS10 tomorrow.

 

[SniperGaulois]

if there is a way to use a sound card I would want to use a program called reaktor that can do any kind of maths and graphs programs with audio

 

[tomv]

Thanks for all the info!

You can find a bit more about sound card scope here:
http://www.zelscope.com/faq.html

Another data logger with nice features:
http://www.dataq.com/products/startkit/di148.htm

But it looks like they give you free razor (hardware, $50) and then make a killing on the software ($200, can't read high-frequency data without it)

Myself, I got the LabJack. Free software, nice device, $129. I'll report how it works when I get it.