FAQ  Donate 
Members List  
Calendar  
Search  
Today's Posts 
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. 

 LinkBack  Thread Tools  Display Modes 
03042009, 04:03 PM  #33  
 
Class 1M Laser Join Date: Mar 2009
Posts: 134
Rep Power: 9 
Xaser But can't you just explain it to me? Cos i've read the page two times, and i cant figure it out. I can easily solve Question 4, but can't 5. Please list the things/terms used for DIY lasers.  
03042009, 04:24 PM  #34  
 
Junior Member Join Date: Feb 2009
Posts: 23
Rep Power: 0 
Bud, theres no real page I can put up and say 'these are laser equations', its all theory that has been dervied from phenomenon and applied to different situations i.e.lighting in your house, to your car battery, to your laser... there all linked with the same basic theory, you cant say that one has its unique special formulae, esp not for building your own laser driver. If you want to know then here I go, Ill try my best: Ill give you my answer and type out a solution Answer to q5: ~80ohms. to work it out: V = IR, transpose this for R therefore: R = V/I , all the currents are given as mA (milli AMPS) BUT to make it easier convert it to Amps by dividing the mA by 1000 (also 10^3 or you can multiply by 10^3, note: ^ means to the power). Then take the voltage and divide by the current to get the resistance. Once you work it out for all, you will see its approx 80ohms. Now if you look at q3 and q4, you will notice the pattern. The current is directly proportional to the voltage in any linear conductor at uniform temperature < ohms law. so in q4 when the resistance decreased to something like 200ohms, shows that it was not probably not a resistor. Because for a 50 volt increase at 500ohms (from q3) the current would be 0.1A or 100mA, directly proportional. If you want an idea of how fundemental this is: Onboard merchant vessels, we still use pneumatic (air) controllers and actuators because the heat (more heat = more resistance for electrical componenets) from the engine room is enough to throw out the more sensitive electrical components. We use electrics to do a lot, but still make use of old fashioned air operated devices. It all really comes down to basic laws like ohms law. God willing this makes sense.  
03042009, 06:51 PM  #35  
 
Class 4 Laser Join Date: Sep 2008 Location: Quebec, Canada
Posts: 15,756
Rep Power: 41801  Quote:
Jerry[/quote] We had some fun in PM's, Jerry *8) Peace, dave **EDIT** *and Nate handles frustration in a very mature manner.[/quote] I'd imagine.... : Just saw this... ;D ;D ;D 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  
03042009, 07:23 PM  #36  
 
Class 3R Laser 
Has anyone used the water analogy to explain everything yet? http://en.wikipedia.org/wiki/Hydraulic_analogy Have a read through here and learn the concepts. It's not a scientific way by any means but it will help you get acquainted with the concepts of electronics. From there, you may want to buy a rapid prototyping board and some simple components, and just get used to working with electronics in reality. There are some very good "starter" projects you can do with discrete components, that you may find fun to build and be able to learn from. The more you practice the better you get... Once you start using maths to describing your electronics work (and get it correct!), and fully understand voltage, current and resistance, then you will be betterprepared for anything this forum will throw at you. When you make the move from cheap and simple compnents to laser diodes, you should know that laser diodes don't follow some of the principles that many other components do, and that parts won't always operate in the ways they say they should. The best example of this is ACDC wall adaptors  they may say that they are outputting 9V, but you shouldn't base your maths on this being correct! Also, you will find that an AC adapter will output a "dirty" voltage, meaning it will fluctuate as it runs, and so needs a capacitor to "smooth" these harmful spikes. I suspect that once you're at this level of thinking, you will come back to this thread and realise just how much you've learnt. That will be when you're ready to build a laser for yourself. Remember that we can tell you all the facts and figures about the lasers and drivers, but unless you understand them and can learn and use the knowledge we give you, there's no benefit whatsoever.
__________________ If I use too many brackets (like this) then just ignore what's inside them...  
03042009, 07:30 PM  #37  
 
Class 4 Laser Join Date: Sep 2008 Location: Quebec, Canada
Posts: 15,756
Rep Power: 41801  Quote:
It says..... P5. * The data below are all taken from measurements of the same resistor. * What is the value of the resistance? * * * * * * * * * * * * * * * * * * Voltage (v) * Current (ma) * * * * * * * * **My Calcs (R=V/A) * * * * * * * * * * * * * * * * * * * * 0.95 * * * * * * * *12.0 * * * * * * * * * * * * * 79.1666 ohms * * * * * * * * * * * * * * * * * * * * 2.03 * * * * * * * *24.8 * * * * * * * * * * * * * 81.8548 ohms * * * * * * * * * * * * * * * * * * * * 2.99 * * * * * * * *37.1 * * * * * * * * * * * * * 80.5929 ohms * * * * * * * * * * * * * * * * * * * * 5.11 * * * * * * * *60.0 * * * * * * * * * * * * * 85.1666 ohms Then to get 100% on the Test... their answer is 83 Ohms.... :? :? :? Have I missed something or are their values in error... :? 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  
03042009, 07:37 PM  #38  
 
Junior Member Join Date: Feb 2009
Posts: 23
Rep Power: 0 
Hey charlie. Yeah a few posts back "Think of it as PRESSURE in a water pipe, when you loose that pressure THATS IT MATE you've had it, your not going to have any flowing water. So the voltage allows the current to flow, thats it." It is a good way to describe the voltage. The voltage that you see comming out from the 'wall', your 9V, is exactly what you use for calculations... its the Root Mean Squared value, and that is the appropriate heating effect of the AC circuit compared to its DC equivalent. And to work that out : Vrms = Vpeak / root2 or Vpeak = Vrms x root2 You wouldnt really ever work with peak values, the RMS is what is used for majority of calculations. Also about AC rectification, majority of adaptors (apart from some ancient ones, so were not talking about common laptop adapters here) do come with capacitors, its called 'capacitor smoothing' and thats used after the 'bridge rectifying'. Edit: Yeah Jerry, hehe, thats what I got. Not sure why its 83. The mean of all the answers isnt even 83. Edit 2: Take the average of all the Volts, Take the average of all the currents, Find out the final resistance = 82.7, round it up to 83. Thats where they've got it!  
03042009, 07:41 PM  #39  
 
Class 3R Laser 
I tried that too, and you're right, those values you listed should be correct. Their marking page wants 83 ohms. I'd avoid relying on that site for any accurate info, if they can't handle V=IR then what hope is there? ;D
__________________ If I use too many brackets (like this) then just ignore what's inside them...  
03042009, 07:42 PM  #40  
 
Junior Member Join Date: Feb 2009
Posts: 23
Rep Power: 0 
Idd. I think there after an average anyway.
 
03042009, 07:54 PM  #41  
 
Class 1M Laser Join Date: Mar 2009
Posts: 134
Rep Power: 9 
Okay, i'll read on your last post tomorrow, and i'll maybe get some "starter" items i can play around with to get it in praxis. I get the q5 now, i just couldn't figure out that i should make it amps (Stupid me..) Well, i didn't really thourd that i should learn more than calculate ohm(put on resistor), choose the right voltage and the right current.. but maybe there's more than that for simple circuits and drivers..  
03042009, 07:59 PM  #42  
 
Junior Member Join Date: Feb 2009
Posts: 23
Rep Power: 0 
Hehe Buddy theres WORLDS more! It is exciting when you get into it. Ive started 6.6kV or 6600V (thats ~9300V peak ac) motor and steam generators at work, it is good!
 
03042009, 08:37 PM  #43  
 
Class 4 Laser Join Date: Sep 2008 Location: Quebec, Canada
Posts: 15,756
Rep Power: 41801  Quote:
then round up the calculated Resistance value... :? It is extremely confusing to the New Members who want to learn the Basics... when simple equations don't add up... The question #5 should have been phrased a little clearer... *since the previous questions dealt with exact calculations... @jonasa0601... I see that you ARE reading... that is a great start... [smiley=thumbsup.gif] 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  
03042009, 11:21 PM  #44  
 
Class 4 Laser Join Date: Oct 2007 Location: Oregon, USA
Posts: 5,478
Rep Power: 2687 
Those "fractional volts" reminds me of an old joke about the difference between mathematicians, (physical) scientist, and engineers, which goes something like this: A mathematician, physical scientist, and engineer were all asked: "What is pi?" Mathematician: "The ratio between the circumference of a circle and its diameter." Scientist: "How many significant digits? To five, it's 3.1416." Engineer: "About three."
__________________ You must spread some Reputation around before giving it to <person> again.  
03052009, 05:15 AM  #45  
 
Class 1M Laser Join Date: Mar 2009
Posts: 134
Rep Power: 9 
On the same page as before theres some more questions longer down.. something with colors on resistors, and i don't get it.. I've read it twice but can someone explain it to me?
 
03052009, 08:11 AM  #46  
 
Class 1M Laser Join Date: Oct 2008 Location: Australia
Posts: 134
Rep Power: 10 
50 dollars is very ambitious you may be looking at 100 dollars
__________________ IN THE VALLEY OF THE BLIND THE SIGHTED MAN WEARS OEM 7+ OD LASER SAFETY GOGGLES MXDL PHR @ 190ma Rayfoss Host Green @ 50mw Mini Sterops LOC @ 200maish LOC project box unlimited duty cycle, Tec and Cooling fan 2 X Rayfoss hosts 1 X Cree stailess steel host PHR pen style @ 100ma + tons of parts  
03052009, 10:50 AM  #47  
 
Class 4 Laser Join Date: Oct 2007 Location: Oregon, USA
Posts: 5,478
Rep Power: 2687  Quote:
These are the most basic fundamentals of electronics. *But even more fundamental is the ability to find and decipher information on your own, without having people hold your hand. *If this is too much for you, you shouldn't be making highpowered lasers. *Come back when you have some problem solving maturity.
__________________ You must spread some Reputation around before giving it to <person> again.  
03052009, 10:55 AM  #48  
 
Junior Member Join Date: Feb 2009
Posts: 23
Rep Power: 0  Quote:
These are the most basic fundamentals of electronics. But even more fundamental is the ability to find and decipher information on your own, without having people hold your hand. If this is too much for you, you shouldn't be making highpowered lasers. Come back when you have some problem solving maturity.[/quote] Im glad you said it, I didnt have the heart too!!  
Thread Tools  
Display Modes  
 