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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
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
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