Thread All new 2019 Super Duper Sperm thread!

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It's that time of year again!

Amazon couriers flinging packages at your house and leaving them out in the rain.

Most of the ones here actually come up to the door
The usps folks usually get about 6-8 steps from the door then just fuckin chuck it at the porch
They do look pretty worn out tho, so I guess I can understand, but then a few of them look like they could use those extra 6-8 steps per house
 
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7 vs 8 caps in series doesn't affect the math much. You should be fine leaving the resistors out, I'd make a 'shorting stick' for shorting the caps out if you are gonna futz with them after running the coil, though.

Neon sign transformer, eh. Bend a couple wires, stuff them in a piece of plastic or something else that's reasonably non-conductive and make a jacob's ladder.
Apparently I have the wrong kind of transformer for the project.

So, I built a 60Hz square wave generator out of a spare Arduino this morning (yeah, just tone(pin, frequency); as even if it's 0.5% off, what difference is that gonna make to a shit old transformer from the 1970s?), and am using that plus an old 300W ATX PSU to juice up a spare ignition coil I had in the garage. Got the arduino flashed, got the 2N3055 wired up, just need to get the wires lined up and some terminals crimped on so that it's at least _sort of_ safe. I have no idea about the output of the ignition coil, only that it's 0.8 ohms on the primary winding, and about 100k ohms on the secondary.
 
Apparently I have the wrong kind of transformer for the project.

So, I built a 60Hz square wave generator out of a spare Arduino this morning (yeah, just tone(pin, frequency); as even if it's 0.5% off, what difference is that gonna make to a shit old transformer from the 1970s?), and am using that plus an old 300W ATX PSU to juice up a spare ignition coil I had in the garage. Got the arduino flashed, got the 2N3055 wired up, just need to get the wires lined up and some terminals crimped on so that it's at least _sort of_ safe. I have no idea about the output of the ignition coil, only that it's 0.8 ohms on the primary winding, and about 100k ohms on the secondary.
Make sure you set the 60Hz output to a duty cycle that gives you a dwell time the ignition coil would typically be used at.

60Hz is fine (corresponds to 1800RPM on a 4 cylinder engine, I s'pose)
 
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Make sure you set the 60Hz output to a duty cycle that gives you a dwell time the ignition coil would typically be used at.

60Hz is fine (corresponds to 1800RPM on a 4 cylinder engine, I s'pose)
Hmm, tone generates a 50% duty cycle. That might be a little on the grunty side for a coil.
 
@gee, is there a way to calculate the theoretical step-up for the transformer based only on the resistances of the coils?

Using that and some back-of-the-envelope math, I should be able to limit the voltage based on the duty cycle of the arduino, right?
 
Not really - an ignition coil acts as a flyback transformer.

Typically they're 100:1 turns ratio. When you put 12V into the coil, it outputs a fairly low voltage corresponding to the turns ratio (say, -1200V) on the output, not enough to cause an ignition spark. But at the same time, the current increases in the primary and the ignition coil "magnetically charges up".

When you disconnect the 12V from the coil, the magnetic charge built up in the coil wants to go somewhere. The input might spike up to 60V, and the output will probably hit +6000V. This voltage is only really limited by the ignition voltage at the spark plug, or the maximum voltage of the transistor driving the primary side of the coil.

I'll probably have to sketch and take a pic of this for it to make sense.
 
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Not really - an ignition coil acts as a flyback transformer.

Typically they're 100:1 turns ratio. When you put 12V into the coil, it outputs a fairly low voltage corresponding to the turns ratio (say, -1200V) on the output, not enough to cause an ignition spark. But at the same time, the current increases in the primary and the ignition coil "magnetically charges up".

When you disconnect the 12V from the coil, the magnetic charge built up in the coil wants to go somewhere. The input might spike up to 60V, and the output will probably hit +6000V. This voltage is only really limited by the ignition voltage at the spark plug, or the maximum voltage of the transistor driving the primary side of the coil.

I'll probably have to sketch and take a pic of this for it to make sense.
So in that case, the thing that's gonna protect the capacitor bank is the spark gap in the Tesla coil, in other words.
 
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