[snip]
Back in my capacitive discharge ignition system days, I'd roll my own on old filament transformer E-I bobbins, shim them up to what I wanted. When they worked the way I wanted I'd hand them off to Arizona Coil to knock me out a few hundred for demos.
My favorite size was 5mH at 5A... 62.5mJ... just the right kick for a spark ;-)
There were times when all the police cars in Detroit were running on one or another model of my ignition systems (Motorola and Philco-Ford days).
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine Sometimes I even put it in the food
Yeah, that makes more sense. I was thinking 1:1 current; don't know why.
I don't know how much of an issue the peak current will be, but you can just increase the pulse width and inductor size if that's an issue. E.g.
2ms and 7.2mH gives 1.3A peak, 146mA RMS.Also, I'm using 5V, which ISTR is what the OP said.
Regarding the current spike, the capacitor is also worth worrying about. In the event that the capacitor fails open, the next pulse is going to produce a rather nasty voltage spike.
That certainly makes the timing simpler.
Good point--this
I like iron for slow stuff like this.
I'm up to my ears in a project right now, commenting here as simulations sit there and churn.
My thoughts are that this hammer driver could be attacked very much like a CD-ignition (see my web site)... generate the energy just as needed... whack the bottom of the coil to -120V, top of coil tied to
+5V....Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine Sometimes I even put it in the food
That's pretty much what Nobody and I've been up to, with a few variations. If John Nagle (the OP) doesn't mind scrounging or winding an inductor, our work is done.
I Googled 'lightly' for laminated core inductors and learned that those wound with hard-drawn copper _sound_ better too. Something about added 'crispness' and 'brilliance,' I think. So that's nice to know. :-)
Cheers, James Arthur
Yep, and it's more power efficient during the steady-state. I used +12v for speed and convenience.
a)
b)
It a) is, and b) will. A nice film cap should do well and last forever.
Cheers, James Arthur
Part of my ignition system timing is by current sense, dumping the appropriate energy into the capacitor.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine Sometimes I even put it in the food
As one option your large +120v supply could be replaced with a much smaller unit at this point.
If the selector coil can take it you could even cobble a 1:1 isolation transformer out of back-to-back wall warts or some such, and use +170v. That'd be easy, with parts that are widely available. A 1:1 audio transformer might even do for just a few mA (check the ratings carefully first!). The switcher uses jelly-bean parts as well--nothing that's hard to get.
The boost-inductor circuits are simpler and slick, but you might have to scrounge for or make the boost inductor. JT was right that--8mJ inductors are available, but not quite as dirt-common as I'd thought.
Cheers, James Arthur
Hey, here's one: 900uH, 6.7A, $1.95.
James Arthur
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