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Navrit Bal

Sun Nov 21 2010, 10:50PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

hehe of course xD

Inner Diameter : 18 mm {might be slightly off}
External Diameter : 35 mm
Length : 53 mm
SWG : 14 {wire diameter = 2.07mm}
Wire Weight : 250 g
Wire Length : 8.33 m

EDIT

I just noticed your update, I was writing this when you responded. * 14 SWG not AWG *

Artikbot

Sun Nov 21 2010, 10:55PM

Registered Member #3247 Joined: Mon Sept 27 2010, 09:42AM
Location: Spain
Posts: 137

Wait wait wait. SWG? I used on mines AWG lol

So yep, with 2mm wire you have those results you posted...

By the way, how comes you used such a monster wire? I did some sims on Barry's RLC and you need to get 40-50mF @350V in order to achieve a nice pulse lenght together with an adequate dampening. Quite a lot of energy, tbh.

Greetings,

Alex Smith

Sun Nov 21 2010, 10:58PM

Registered Member #3258 Joined: Wed Sept 29 2010, 06:25PM
Location: Ascot, UK
Posts: 25

I used 2mm wire with 18mF @50V :D Worked great!

Navrit Bal

Sun Nov 21 2010, 11:01PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

I thought it would be best to use a big wire, then add resistance with resistors as needed. Also, I have 3 450V 1.8mF capacitors and 105 330V 160uF photoflash capacitors (16.8mF overall). Where did the 350V come from?

Artikbot

Sun Nov 21 2010, 11:01PM

Registered Member #3247 Joined: Mon Sept 27 2010, 09:42AM
Location: Spain
Posts: 137

50V is pretty low, so dampening is not as critical (back EMF is nowhere as destructive unless you're talking about several dozens of amsp) as if you use higher voltages.

It all depends on the balance of both

Navrit Bal

Sun Nov 21 2010, 11:06PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

Is it actually a good idea to do that? (add resistance to achieve a target value)

Artikbot

Sun Nov 21 2010, 11:33PM

Registered Member #3247 Joined: Mon Sept 27 2010, 09:42AM
Location: Spain
Posts: 137

Quoting ScotchTapeLord, some people do add resistors to their cemf protection diodes in order to lenghten pulses, but they seem to kill efficiency aswell. You could try with some ceramic resistors, Farnell has 25W ones for over 1'5 bucks or so.

But considering you're wanting to add them to your coils... unless you put a power resistor there (50kW one will do, your pulse is AWESOMELY high powered), I doubt they will resist the shock. Side note: Power resistors of that size cost up to 400 usd, so no, that's not an alternative.

I would play with thinner wire aswell. I also eyeballed my wire gauge, and somehow I got it right. Two of my coils are nearly critically dampened, and the third one is going to get a capacitance tweak to achieve critical dampening.

I guess doing the math before eyeballing stuff saves lots of trouble

Navrit Bal

Sun Nov 21 2010, 11:42PM

Registered Member #3323 Joined: Sun Oct 17 2010, 03:19PM
Location: West Midlands, UK
Posts: 116

What if I use thinner wire to connect everything together?

Artikbot

Sun Nov 21 2010, 11:49PM

Registered Member #3247 Joined: Mon Sept 27 2010, 09:42AM
Location: Spain
Posts: 137

Hmm.. As long as you don't melt your wires... Remember that you would be essentially converting your wiring onto the new resistors. You would need lots of thin wire aswell.

The best way to achieve critical dampening without killing efficiency nor modifying the coils is increasing capacitance. You just need to find your sweetspot taking into accout diodes capabilities (surge current and surge current time limitations) and pulse lenght.

As long as your diode's capable of absorbing all the energy on the cemf pulse, you're alright with a nowhere near critical dampening. But that would, of course, kill your efficiency.

Play a bit with Barry's RLC sim and decide by yourself what you're gonna take into consideration

klugesmith

Mon Nov 22 2010, 01:26AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Navrit Bal wrote ...

It increments in 0.1 steps. I just touched the connections together and it still reads 0.5, it looks like it might be faulty, I guess I'll have to buy a new one unless someone can suggest something else.

The measurement includes the resistance of the meter probes, which you need to subtract.
Many digital meters can do that for you (push the "relative" button while touching the probes together). Analog meters do it properly when you make the zero-scale adjustment.

The fancy way to measure milliohms is to force a known DC current, say 1 amp, and measure the voltage between the coil ends.

Here is a method that is probably more accurate than the simulator. Weigh your actual coil, and find a wire table that gives "ohms per pound" or "ohms per kg" for your chosen wire gauge.
For RLC dynamics, what counts is the total resistance: coil, switch, capacitor ESR, and all connecting wires. I bet the contribution from your soldering is inconsequential.

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