Has anyone used a STITCH Welder?

[Jim Berquist]

Najam:

Voltage is the driving force or EMF. (E)

Current is the mass. How much electrons are flowing. (I)

Resistance is what causes the heat because that many electrons are flowing through that circuit. (R) Any thing that consumes power expels heat. Energy never goes away it just changes states.


I seen 24 vdc blast a chunk of copper 5/8 thick by 1" wide completely open because some one contacted a ground..those batteries could provide 2ooo amps.hours.....

Jim

[Jim Berquist]

E (electromotive force)

I (current flow creates heat)

R ( Resistance opposes flow and creates heat)

Energy will not go away! It will change states and or move but not go away. It will turn to light, magnetics, heat, or just stuff you can use!!

Yucccc!


The FCC is so disarranged they quit doing there job years ago!

Any arc you create could send a message around the world.!!!

I could show you a spark gap transmitter that could cover the world over and bounce off the moon.......Two D-Cell batteries and a transformer....

This would be no worse then a average arc source!!


Jim

[pezman]

My answer, in reverse so as not to spoil the fun for others (or to avoid public embarrassment, whichever case holds):

senohpdaeh eht fo ecnadepmi eht naht rehgih hcum saw taht ecnadepmi ecruos a dah tuptuo enohpdaeh s'mpa eht

[Najm]

The output current was divided among the 8 headphones when they were rigged in parallel. So their output(power) was lower than expected even if they were having the same voltage across them.

[larry cottrill]

The output current was divided among the 8 headphones when they were rigged in parallel. So their output(power) was lower than expected even if they were having the same voltage across them.

This isn't quite right. Resistors in parallel don't divide up the current, they actually ADD it up! Say you have a 12 volt car battery with an ammeter on it. Shunt a 12 ohm resistor across it and the ammeter will read 1 amp. Shunt (parallel) a second 12 ohm resistor across the first one, and the ammeter will read 2 amps. Twice the current (and twice the total heat , i.e. power, being evolved). Three such resistors will draw 3 amps, and so on. As long as the resistors are equal, they just add equal amounts to the total current draw (as long as the voltage stays constant). This is because the voltage source sees LOWER resistance as you parallel them, and has to supply more current to maintain a stable voltage.

Given a fixed voltage source, it is always the resistances that will determine the current drain (as long as the voltage source is adequate to carry the total current, of course) and thereby determine the power derived. True, the parallel resistors divide up the TOTAL current, but the total current keeps becoming larger as you add more resistors !!!

L Cottrill

[Najm]

The stereo wasn't supplying enough amps for the headphones to work at their maximum potential? I'm guessing.

[larry cottrill]

The stereo wasn't supplying enough amps for the headphones to work at their maximum potential? I'm guessing.

This is getting closer, and is another way of saying what pezman said:

senohpdaeh eht fo ecnadepmi eht naht rehgih hcum saw taht ecnadepmi ecruos a dah tuptuo enohpdaeh s'mpa eht

... which being translated means "The amp's (i.e. the stereo's) headphone output had a source impedance that was much higher than the impedance of the headphones." This is exactly right, except for one small detail: "much higher".

This Heathkit stereo receiver (not a separate power amp) had a 4 OHM series resistor at each speaker output protecting the stereo from accidental short circuit at the output. The headphones were each nominally 8 ohms per channel. (Note: I was using the speaker output because I assumed that the headphone jack didn't have sufficient power to drive 8 pairs of phones.) That mere 4 ohm "output impedance" was enough to mess up my attempt to use the phones in parallel. Recall that in SERIES, resistances carry the same current but divide up the VOLTAGE according to the individual resistances.

Let's say the phones really were 8 ohms. Let's say the stereo's final power transistor pair puts out a signal of 10V peak-to-peak. With a single headphone attached, the total impedance is 12 ohms, 1/3 of which is the protective resistor. So, the headphones will see 2/3 of the 10V signal, or 6.66 V p-to-p. Now, add another pair in parallel. That makes the net headphone impedance only 4 ohms, and the total impedance just 8 ohms - so, the signal voltage across the phones is only 4/8 or 5 V p-to-p! Parallel another two sets of phones onto these and the total headphone impedance is only 2 ohms, for a total impedance of 6 ohms - and the headphone signal voltage is now only 2/6 of the total, just 3.33 V p-to-p !!!

It seemed like such an obvious thing to do, but it was absolutely hopeless.

Attaching the phones in series caused the ratio of external/internal impedance to increase, resulting in acceptable performance. The only disadvantage to this was that when one headphone eventually failed, it killed that whole channel for everyone, and you had to hunt for the bad headphone by trail-and-error - the "Christmas tree light string effect".

Of course, another potential flaw in a series scheme is that you could never rig individual volume controls, but I didn't have that in mind, anyway.

L Cottrill

[Al Belli]

Hi Larry,

Your problem is why commercial sound distribution systems use a 70 volt high impedance output.
Each speaker has an adjustable matching transformer which allows the desired amount of volume / power to be selected.

Al Belli

[pezman]

If you wired the headphones as a series of four pairs in parallel, then the impedance would be reasonably high, the system should survive headphone failures and you could find the failed headphone by listening for the loudest pair:

/\
$ $
\/
/\
x $ <-- This guy gets louder than the others due to failed partner
\/
/\
$ $
\/
/\
$ $
\/


Sorry to have de-railed the thread ... I will resist further headphone commentary unless/until the headphone posts are re-located ...

[larry cottrill]

Sorry to have de-railed the thread ... I will resist further headphone commentary unless/until the headphone posts are re-located ...

The derailing is my fault. I was just hopeful that I could show an amusing example of how surprisingly resistance vs power works out in some situations, not trying to solve a problem I had 30-plus years ago.

This does have a more practical application. All current sources, including power supplies and batteries, have some internal resistance which naturally behaves as a series resistance. This is why voltage levels drop if they are overloaded. It is also basically how batteries degenerate over time and/or usage: The internal chemical reaction still produces exactly the same voltage, but waste products, tiny bubbles, etc. accumulate to drive up the internal resistance. That's why you can't test a battery's condition by just putting a high-impedance voltmeter on it - you have to apply some kind of resistive load across it while measuring the voltage.

L Cottrill

[Jim Berquist]

I am currently working 60 hours a week! As soon as I can find the part I will submit photos of same. Your all trying to make this harder then it is. The one I built was no more then a solenoid with a rod connected to the end. A coil bypass for the solenoid. It worked........



Jim

[Jim Berquist]

This could be improved! I just want to build one like I had and keep it simple for the people that have NOT!!!!! I will Provide when I can....Tired and going to sleep!!!!!

If you all can come up with some thing better help me out here! I could
weld a bike and go cart and even a mini bike with mine... I want to have something that the HAVE NOTS can work with!!!! The one I had would not just do sheet metal!!!!


Not Just sheet metal!!!

Jim

[Jim Berquist]

I have not given up! Still working 55-60 hours a week and have not found the solenoid I want. Don't give up on thread. Has anyone else got one to perform?

Jim

[Jim Berquist]

Found one with Mc Master Carr.. Will order and post results. Jim

[Jim Berquist]

NOT COMPLETED:

STILL WORKING:

DON'T GIVE UP:

JUST ON THE BACK BURNER!

HAS ANYONE ELSE PLAYED WHITH IT?

JIM: