CALLING ALL TECHNICAL NERDS....

Having a technical difficulty? Post here for help or advice.

Moderator: Officers

CALLING ALL TECHNICAL NERDS....

Postby Icyhot on Thu Sep 23, 2010 11:42 pm

So I don't know many people that I could ask about this sort of thing, but I was hoping some of you might be able to fill in a piece of the puzzle.

I was thinking about buying a bathroom scale to take a part and use the load cells out of them :)

I'm not sure what kind they would be, but I assume they probably take some voltage in and send some millivoltage out.

I have some recording equipment for music and I was thinking if I can plug in an electric guitar directly and detect it on my computer surely I can pick up a load cell/strain guage output. nice thing is my recording box has a gain to boost the signal and I don't figure the electrical signal coming off the pickups of a guitar are much different in their magnitude as the signal is generated by vibrating strings.

"The output voltage of most pickups varies between 100 mV and 1 V RMS."

So this leads me to soldering some ts connections to the leads and now i have signal going into my compy.

So my question becomes how do I interact with the soundcard through visual studios?

I haven't found much good info from google yet and I was wondering if any of you knew of any good resources... namely code examples of how to read a sample from the soundcard buffer and write it to a file and display the value on screen in real time as well as graphing that. I figure it can't be too hard because my recording software does most of the minus the value.... you can see the wave form. so it is graphing and writing to a file. At the moment I don't have any need for sending signal back, but I might want some. If this works... I was looking to make a homemade Dynamometer for testing car engines.

Of course if any of you knew of a way of picking up some new DAS/DAQ hardware and software for less than 200 bucks let me know.
I(Jesus Christ) have come as Light into the world, so that everyone who believes in Me will not remain in darkness. If anyone hears My sayings and does not keep them, I do not judge him; for I did not come to judge the world, but to save the world. - John 12:46-47

God demonstrates his own love for us in this: While we were still sinners, Christ died for us. - Romans 5:7-8
User avatar
Icyhot
Clan Member (AKA Barfbag)
 
Posts: 198
Joined: Tue Oct 30, 2007 7:32 pm

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] Scubadvr on Fri Sep 24, 2010 9:51 am

Sounds like you need an Electrical Engineer. I aren't one.
Image
Psalm 66:1,2
Ecclesiastes 5:18-19
"Since all have sinned and fall short of the glory of God; they are now justified by his grace as a gift, through the redemption that is in Christ Jesus." Romans 3:23-24
User avatar
[CS] Scubadvr
Clan Officer
 
Posts: 5611
Joined: Wed Apr 26, 2006 10:26 am
Location: Missouri

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] No One on Fri Sep 24, 2010 10:20 am

There are probably others on this site that can offer more insite. It's been a while since I have done any work with load cells.

If you could give me some idea of what you are trying to do with the cells that might help.

What you are talking about is likely a compression load cell. I don't know much about the scales you buy but the cell could be digital or analog.

What you in effect are doing with the gain is making a load cell amplifier. You would need to be careful with this as the load cell and the amplifier need to be calibrated together. I'd have to give some thought on how to do this especially if either the cell or the amplifier is non linear in the ranges you are working.

You might want to see if you can google a part number from the cell when you get it. That might tell you the operating range of the cell, input voltage, and output parameters.

You might be able to pick up a cell from someplace like digikey. Digikey may have some kind of DAC harware and software that may be semi affordable.

As far as programming I wouldn't have a clue. There may be semi affordable devices available that can convert cell output to say a USB style of input. Then I would think you could use just about any programming language to take advantage of the that device.
User avatar
[CS] No One
Clan Officer
 
Posts: 1605
Joined: Wed Apr 26, 2006 3:19 pm

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] vizwhiz on Sat Sep 25, 2010 1:16 am

Icy...
1. Load cells are "variable resistance" devices. They are actually "strain gauges" built into a structure that can support a load and thus they are called "load cells"...in a strain gauge, the resistance changes as they change shape, so the tiny amount of change in shape from the load changes the resistance...when you put a voltage across it, you get a changing amperage through the load cell (changes with changing load) because the resistance changes. It is essentially an analog signal, but it may be interpreted by either an analog device (simple ammeter, for example) or a digital one. They ARE very small and sensitive, however, but pretty straightforward to understand. They usually require a clean power source and a large shunt resistance because they are so small...but then again, it's been 25 years since I've messed with them too... Nutshell explanation anyway... :D

2. Many bathroom scales still use springs and such...make sure the one you're considering really has load cells in it! :wink:

3. Go HERE...look on the main page for "load cells, strain, etc." and you'll find everything you need, all the devices you want, and the controls... Omega's the place...plus, you might be able to get a free Dilbert desk calendar or something with your order! :mrgreen:

Hope this helps...
Of course I talk to myself...sometimes I need expert advice! (author unknown)
User avatar
[CS] vizwhiz
Clan Member
 
Posts: 2149
Joined: Fri Dec 12, 2008 7:53 pm
Location: Lakeland, Paradise (FL)

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] Joab on Sat Sep 25, 2010 1:19 am

Icy...

You have found the nerd you are looking for.

Image
"A thorough knowledge of the Bible is worth more than a college education." -- Teddy Roosevelt
"There is only one person God has treated worse than He deserved." -- John Piper
User avatar
[CS] Joab
Clan Llama and a Legend in his Own Mind
 
Posts: 12267
Joined: Fri Jan 05, 2007 3:33 pm
Location: NW Ohio, USA, Earth

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] vizwhiz on Sat Sep 25, 2010 1:25 am

Joab! Where'd you get that picture of my dad??? :shock:



8-) Just kidding...but it does kinda look like him when he was younger... I looked like Napolean Dynamite in high school... :(
Of course I talk to myself...sometimes I need expert advice! (author unknown)
User avatar
[CS] vizwhiz
Clan Member
 
Posts: 2149
Joined: Fri Dec 12, 2008 7:53 pm
Location: Lakeland, Paradise (FL)

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] Ice_GopherFC on Sat Sep 25, 2010 7:08 pm

Frosty might have some input... I are wrench turner.
"Blimps remind me of myself to much to want to own one. The are slow, round, full of hot air and not tax free. :shock:" -[CS] Goodytwoshoes

I've learned that I'd much rather have fools pray for me, than work with intellectuals who run me down. I love you folks! (1 Corinthians 1:25!)
User avatar
[CS] Ice_GopherFC
Official Clan Fire Fodder
 
Posts: 1331
Joined: Sun Jun 18, 2006 12:52 am
Location: Crofton, MD

Re: CALLING ALL TECHNICAL NERDS....

Postby Frostbite on Sun Sep 26, 2010 2:58 pm

No One and Viz has already stated the basics. I do not believe any more input could be added right now without ripping a scale apart. As for the programming part, not my area of expertise. That would be more along the lines of the mongoose clan.

Edit: After thinking about it some more, you said you were going to run it through your audio card. BAD IDEA. I am positive that the line in inputs have filters in them that chop off low frequency / dc. This means that if the weight slowly changes you will see nothing on that signal. Also, if you boot up the system you have no idea what the starting weight would be.

The more practical way in my opinion is find a micro controller with an ADC for reading in the voltage levels. Then bus it over to the computer over USB or RS232 (serial).
User avatar
Frostbite
Officially Retired
 
Posts: 1061
Joined: Tue Apr 25, 2006 10:55 pm
Location: UNC Charlotte

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] Scubadvr on Mon Sep 27, 2010 1:43 pm

Or, you could stick your tongue on it and see if it hurts. :P
Image
Psalm 66:1,2
Ecclesiastes 5:18-19
"Since all have sinned and fall short of the glory of God; they are now justified by his grace as a gift, through the redemption that is in Christ Jesus." Romans 3:23-24
User avatar
[CS] Scubadvr
Clan Officer
 
Posts: 5611
Joined: Wed Apr 26, 2006 10:26 am
Location: Missouri

Re: CALLING ALL TECHNICAL NERDS....

Postby Icyhot on Sun Oct 24, 2010 9:51 pm

In case anyone was curious.

http://www.nerdkits.com/videos/weighscale/

So when I originally posted this video I had never messed with a microcontroller, but now am learning... I did find a program to turn your audio card into oscilloscope.

I knew that the voltage out of strain gauge was going to be on the milliVolt level thus the need for my spiffy sound card with built in pre-amps to detect the change. I haven't tried gathering the info out of it in lieu of playing with microcontrollers and learning C.

so many projects so little time and a mountain of a learning curve... I do believe this will be on hold until we figure out how to get fuel injection on a lawn mower enginer.... and then possibly to build our own dyno :)

so far i have figured out how to use the ADC on a micro to read a changing voltage of a temp sensor and display it on a LCD...
I(Jesus Christ) have come as Light into the world, so that everyone who believes in Me will not remain in darkness. If anyone hears My sayings and does not keep them, I do not judge him; for I did not come to judge the world, but to save the world. - John 12:46-47

God demonstrates his own love for us in this: While we were still sinners, Christ died for us. - Romans 5:7-8
User avatar
Icyhot
Clan Member (AKA Barfbag)
 
Posts: 198
Joined: Tue Oct 30, 2007 7:32 pm

Re: CALLING ALL TECHNICAL NERDS....

Postby [CS] No One on Mon Oct 25, 2010 8:27 am

What kind of dyno are you trying to build?

About 8-9 years ago I built an inertial dyno for gokart engines. Its really not too hard to build a dyno if you are dealing with a fixed weight where you can use in inertial type dyno. The hardest part is getting the data acquisition system to work properly.

Fuel injection on a lawn mower wouldn't be too difficult depending on what size engine you are talking. The hardest thing is getting control of the timing. The next hardest thing would be finding properly sized injectors, pump, etc for an engine that small. I think it could be done. It would take some tinkering around to get everythign working but it might be kind of a fun project.

:D
User avatar
[CS] No One
Clan Officer
 
Posts: 1605
Joined: Wed Apr 26, 2006 3:19 pm


Return to Support/Help

Who is online

Users browsing this forum: No registered users and 1 guest

cron