Laser pointer discussion. Read/write reviews of laser pointers and laser pointer companies. Learn about all types of laser pointers and lasers





Welcome to Laser Pointer Forums! If you are looking for a laser pointer or want to compare different laser pointer companies, you may want to check out the LPF Laser Pointer Company Database. The link will open in a new window for your convenience.








Green Laser Pointers by Category Blue Laser Pointers by Category Red Laser Pointers by Category
Yellow Laser Pointers by Category Violet Laser Pointers by Category Orange Laser Pointers by Category
Top Laser Pointers by Power - 1 Watt+ Top Laser Pointers by Power - 500mW+ Top Laser Pointers by Power - 250mW+
Laser Pointer Database High Power Laser Pointers Laser Pointer Diodes
Laser Technology Laser Pointer Parts Lasers by Wavelength
Top 10 Laser Pointer Companies Laser Pointer Company Database Visible Beam Laser Pointers


One laser store meets all your needs

























Go Back   Laser Pointer Forums - Discuss Laser Pointers > Lasers > Drivers, Test-load, Power Supply, & Batteries



LPF List of Laser Pointer Companies (link opens new window)



Reply
 
LinkBack Thread Tools Display Modes
Old 08-26-2011, 08:10 AM #1
Isoleucine's Avatar
Class 1M Laser
 
Join Date: Jul 2010
Location: Southern California
Posts: 234
Rep Power: 20
Isoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud of
Isoleucine Isoleucine is offline
Class 1M Laser
Isoleucine's Avatar
 
Join Date: Jul 2010
Location: Southern California
Posts: 234
Rep Power: 20
Isoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud of
Default Direct Drive/Measuring in Test Load - Tips

Hello all.

I've been doing a lot of research lately and I found out a few things.

Say you're building another death ray that needs a fairly high amount of voltage. Or current. Or both. Well, the main problem that happens with high voltage projects, and/or direct drive builds is the resistance that tends to build up in thinner wires. Wikipedia has a nice store of info for various resistances across many wire gauges (AWG). So in short, the wider the wire, the LESS resistance it has. And with different metals, the resistance could vary as well.

American wire gauge - Wikipedia, the free encyclopedia

Well, typically there is a slight problem, as people don't know their exact wire gauge, as the insulation around it could vary... and a whole lot of other factors. People also tend use the resistance function on DMMs when they are trying to measure resistance. This is wrong for a reason. With the wires and internal PCBs also in the measuring circuit, the resistance reading is unreliable and not very accurate at all, in fact the resistance is higher than the actual resistance in the wire you are measuring. Not even top-of-the-line DMMs can measure the resistance accurately.

However, this should be known to all people who are doing a direct drive or something similar that uses a lot of current and needs a very low resistance. The correct way to measure the resistance across a piece of wire or just any plain resistor without the interference of the cables is called four wire resistance measurement. This method uses voltage measurement to bypass the resistance in the wires. And also, its almost the same when us laser-using people set drivers with test loads. What happens is typically, a current of exactly 1 ampere is pushed though a wire or unknown resistor value. Then a DMM measures the voltage across the unknown resistor. be sure to note that you want to measure wires at the very tips so that you know the resistance of the entire piece of wire, since wire is like a resistor... in a way. This works for a very, very simple reason.

Ohms law.

V = IR.
Where V is voltage, I is current, and R is resistance. For all of you who don't understand this, please do not use lasers in any way, fashion, or form (I have a cousin who keeps playing with my lasers with his stupid foolishness). Rearranging the formula gives us

V / I = R.

Since the current is exactly 1 ampere, it can be eliminated from the equation.
Where V = R. The voltage value is equal to the resistance, whether it be 1 volt, 1 millivolt, 1 microvolt, which translates into 1 ohm, 1 milliohm, 1 microhm, and so forth.

If your behind is too large to even read all that, you should really consider doing the research for yourself. Here's a great video by afrotech. He makes other videos on electricity that can REALLY help you in building lasers. He also includes a bit of humor in his videos for a nice laugh. Also with subtitles.

4 wire (Kelvin) resistance measurement tutorial - YouTube

Thats it for that, and have fun with building new death rays for all us laser-lovers to see... phatlights tooo.

___

For the next part for all you new people, using the above method is one thing, but also its a useful device to measure current... once you rearrange everything up.

The above equation V = IR is ohm's law. Use it a lot.

Typically, you will need rectifier diodes (usually a few 1N4001 s) to simulate your diode's forward voltage drop, and a 1 ohm resistor. Since the current is the unknown and the resistor value is constant, you can find out the current easily by, once again rearranging ohm's law. This time...

V / R = I

And since R is 1 ohm, V = I ... where it may be 1 volt, 10 volts 100 volts whatever, and translated to 1 amp, 10 amps or even 100 amps, which is terribly unsafe for anyone working with lasers.

Thats it, now enjoy your new test load tips, lasers, death rays and other various sorts of light emitting sources... or just anything at all.


Iso



Last edited by Isoleucine; 08-26-2011 at 08:16 AM.
Isoleucine is offline   Reply With Quote







LPF List of Laser Pointer Companies (link opens new window)







Old 08-26-2011, 12:08 PM #2
lasersbee's Avatar
Class 4 Laser
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 15,743
Rep Power: 41315
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
lasersbee lasersbee is online now
Class 4 Laser
lasersbee's Avatar
 
Join Date: Sep 2008
Location: Quebec, Canada
Posts: 15,743
Rep Power: 41315
lasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond reputelasersbee has a reputation beyond repute
Default Re: Direct Drive/Measuring in Test Load - Tips

Thanks for that.... I see you have done a lot of
research...

The Video is very informative to measure in the
mOhm ranges...

As to test Loads that nominally use 1 Ohm resistors..
have you seen this from 12/30/2008.....

Current

or these.....



WTB: Test Load (AKA "Dummy load") PCB

http://laserpointerforums.com/f39/fs...p-3a-63450.htm

FP Super 3 amp Test Load

http://laserpointerforums.com/f39/3a...ock-65885.html


Laser Diode Tests loads and how to use them have been
around for quite a while....


Jerry
__________________

J.BAUER Electronics Home Page

LaserBee Laser Power Meter Products meet your needs
at affordable Prices:
See them all here on LPF

LaserBee Power Meter products ALWAYS in Stock
and ready to ship

Also available on eBay:Check availability here..

Subsidary: Pharma Electronic Solutions


This banner is available to and can be copied/used FREE by any LaserBee owner

Last edited by lasersbee; 08-26-2011 at 12:15 PM. Reason: Spelling errors
lasersbee is online now   Reply With Quote
Old 08-26-2011, 12:29 PM #3
Benm's Avatar
Class 4 Laser
 
Join Date: Aug 2007
Location: Netherlands
Posts: 7,437
Rep Power: 18210
Benm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond repute
Benm Benm is online now
Class 4 Laser
Benm's Avatar
 
Join Date: Aug 2007
Location: Netherlands
Posts: 7,437
Rep Power: 18210
Benm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond reputeBenm has a reputation beyond repute
Default Re: Direct Drive/Measuring in Test Load - Tips

Measuring like displayed above is actually pretty much the same as the 4 wire method for measuring resistance, but the other way around: You have a resistor of know value and measure the voltage across it to get the current.

This approach is very accurate as the input resistance of the multimeter is typically very high and does not interfere with the measurement. Accuracy is limited by the tolerance of the resistor... and though most are rated 5% tolerance, typical deviation from nominal is in the order of 1%.
Benm is online now   Reply With Quote
Old 08-26-2011, 02:03 PM #4
Bluefan's Avatar
Class 3R Laser
 
Join Date: Aug 2009
Location: The Netherlands
Posts: 1,482
Rep Power: 62
Bluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond repute
Bluefan Bluefan is offline
Class 3R Laser
Bluefan's Avatar
 
Join Date: Aug 2009
Location: The Netherlands
Posts: 1,482
Rep Power: 62
Bluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond reputeBluefan has a reputation beyond repute
Default Re: Direct Drive/Measuring in Test Load - Tips

Quote:
Originally Posted by Isoleucine View Post
... Not even top-of-the-line DMMs can measure the resistance accurately .... The correct way to measure the resistance across a piece of wire or just any plain resistor without the interference of the cables is called four wire resistance measurement. ...
Top-of-the-line DMM's all have 4 wire resistance measurement. My Keithley 199 DMM's have a 1mOhm resolution and 4 wire ohms measurement, usefull to determine the exact resistance of sense resistors.

Last edited by Bluefan; 08-26-2011 at 02:04 PM.
Bluefan is offline   Reply With Quote
Old 08-26-2011, 04:12 PM #5
Cyparagon's Avatar
Class 4 Laser
 
Join Date: Sep 2007
Location: Wisconsin
Posts: 9,142
Rep Power: 9321
Cyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond repute
Cyparagon Cyparagon is online now
Class 4 Laser
Cyparagon's Avatar
 
Join Date: Sep 2007
Location: Wisconsin
Posts: 9,142
Rep Power: 9321
Cyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond reputeCyparagon has a reputation beyond repute
Default Re: Direct Drive/Measuring in Test Load - Tips

Quote:
Originally Posted by Isoleucine View Post
people don't know their exact wire gauge, as the insulation around it could vary...
Wire strippers and caliper

It's not as precise if the wire is stranded, but almost all wire gauge is a multiple of 2, so you can round. That silicon 26 awg is common. 4 inches of 26 awg is ~13mΩ. So it only wastes 40mW of heat (0.5% loss of power) at 1.8A
__________________
A problem well stated is a problem half solved.
Cyparagon is online now   Reply With Quote
Old 08-26-2011, 04:41 PM #6
Elektrotechniker's Avatar
Class 3B Laser
 
Join Date: Nov 2008
Location: Germany
Posts: 4,240
Rep Power: 409
Elektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond repute
Elektrotechniker Elektrotechniker is offline
Class 3B Laser
Elektrotechniker's Avatar
 
Join Date: Nov 2008
Location: Germany
Posts: 4,240
Rep Power: 409
Elektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond reputeElektrotechniker has a reputation beyond repute
Default Re: Direct Drive/Measuring in Test Load - Tips

Awesome thread! I need to understand this in depth sometime. Really helpful just with one look
Elektrotechniker is offline   Reply With Quote
Old 08-26-2011, 08:30 PM #7
Isoleucine's Avatar
Class 1M Laser
 
Join Date: Jul 2010
Location: Southern California
Posts: 234
Rep Power: 20
Isoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud of
Isoleucine Isoleucine is offline
Class 1M Laser
Isoleucine's Avatar
 
Join Date: Jul 2010
Location: Southern California
Posts: 234
Rep Power: 20
Isoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud ofIsoleucine has much to be proud of
Default Re: Direct Drive/Measuring in Test Load - Tips

To address all of you without quotes...

This thread is just on how to do 4 wire measurement. And yes, I've read about a lot about testloads, seen most if not all the pictures by ROG8811, read all the old threads, and seen most of the videos that LPF members make... and abused the search bar to the point where my broswer crashed once.

Sometimes, just doing the 4 wire measurement may just bypass all of the caliper measuring and other stuff. But yes, measuring with a caliper is useful if you are terribly unskilled at using a DMM, yet you can do math well. And lastly, the DMMs that I deal with are NOT reference DMMs. Just handheld ones made by various companies. Those reference DMMs are super-out-of-my-price range and scope. Pardon that.
Isoleucine is offline   Reply With Quote
Reply





Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On











Loading








Green Laser Pointers by Category Blue Laser Pointers by Category Red Laser Pointers by Category
Yellow Laser Pointers by Category Violet Laser Pointers by Category Orange Laser Pointers by Category
Top Laser Pointers by Power - 1 Watt+ Top Laser Pointers by Power - 500mW+ Top Laser Pointers by Power - 250mW+
Laser Pointer Database High Power Laser Pointers Laser Pointer Diodes






Privacy Policy | Advertising Disclaimer | Terms of Use


 


All times are GMT. The time now is 05:38 PM.


Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO
Privacy Policy | Advertising Disclaimer | Terms of Use
Copyright (C) 2017 Laser Pointer Forums, LLC