--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
To get a much bigger spark with one coil it would need to dispate a lot more power, when its not sparking its drawing direct current wich is wasted power, maybe you could have variable dwell angle to save power though but thats probably more dificult. many ignition systrem just replace the points with a sensor and transistor wich is a big improvement on its own, but CDI gives much more rapid and powerfull spark.
You know... it just occurred to me... I can light an LED with it.
NOW people will pay attention ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I hardly need Spice to understand how a thing like this works.
The inductor current builds as something like Vb/Ton, and the spark energy goes as I^2. So low battery voltage, as in cold cranking, would seem to need a longer (not higher current) base drive. Spice that!
Store it in the coil, like people have been doing for a century now.
Not if you want to get to work every morning.
Actually, it's tricky to get high stepup ratios in circuits like this. As the boost ratio increases, energy gets lost in the various parasitics. You're suggesting a 100:1 boost (4v cold cranking, 400v peak out) and that's pushing things.
To save a lot of size and money; neither the L nor the C will cost pennies. Does any carmaker actually do it this way?
Jim's circuit really is very elegant, John. Do it in SPICE - then you see how well he has done.
You don't need a current sensor or fancy drive electronics. Just make the base current sufficient to make a spark at worst-case ambient temp, battery voltage, and include a fudge factor for old ladies who never got around to switching their summer weight 40W100 oil.
Then how do you get a spark? Where is the energy storage?
In Jim's circuit, all you need is a fixed width base drive to saturate the tranny.
His circuit wastes the first trigger pulse. After that, 400V is sitting on the collector waiting for the leading edge of a trigger to dump the charge into the ignition coil.
I love circuits like that! Brilliant. Elegant. Even I can understand how they work. Bulletproof. Minimum parts count. Pennies for the components.
I don't really remember for sure now. For inductive storage driven by a transistor, they're ~5mH. I believe off-the-shelf coils are about the same inductance.
My "CD", using 5mH for "charging" and an off-the-shelf coil, will blow a droplet of oil out of a spark-plug gap, and will burn a hole straight through 1/8" plexiglass.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
INDUCTIVE charging, so John's ratio is meaningless
4V Cranking is for real... COLD
Operating temperature range -40°C to +140°C
Actually, in the winter time, Arizona will have the record high AND LOW temperatures for the day. Out desert regions, like Phoenix, will have the high temperature, and a place called Hawley Lake up in the White Mountains will be at -40°F at the same time ;-)
[snip]
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
"all you need is a fixed width base drive to saturate the tranny."
Can't remember who.
Someone else here cited the 4V. Sounds reasonable to me. I hate to hike in the snow.
Sooms to me that two inductive components are not the same thing as one inductive component. Do you disagree?
I think Jim said it wasn't his design.
Complexity, barely; weight and cost, absolutely not. This is a big inductor, because it has to store *all* the shot energy all at once.
If I wanted to go CD - and I'm not sure why I would - it seems more sensible to use an oscillating flyback converter with a small ferrite step-up transformer and voltage feedback to charge the cap. Silicon is practically free, but the 5 mH inductor will be a beast.
This is a wonderful, fun, clever circuit. It's just not very practical. Things like that are often hard to let go of, but if it's not a good engineering choice, it must be let go of.
Even if you figure only 2.5V available for the inductor during crank, you get to 5A in 10ms, quite adequate for starting. At (600RPM) idle a V8 has 25ms between firings.
You doth exaggerate, it hasn't been over 92°F this month ;-)
I've only seen > 120°F here two days out of the 43 years I've lived here.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Not my CONCEPT. But I, as they say, "reduced it to practice".
[snip]
Get over it, John. It IS very practical for someone spinning their own.
It made it into Ford's racing cars, but not into production vehicles... not because of cost or size, but due to Ford's concern that poorly maintained vehicles would start misfiring due to the short spark duration.
They were wrong about that. (Some of the managers I had to deal with were engineers who had worked for Ford since Henry the First :)
But my inductive storage method based upon the "charge coil, hold current, adjust turn-on point" method is still in use 35 years after I designed it.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Good thing you smilied that one. I'd have to be seriously drunk to get confused over anything this simple.
Boost step-up ratios are not meaningless. High ratios get expensive, which is why people tend to prefer transformers for high Vout/Vin ratios on dc/dc converters.
This circuit is cute and clever, and one could certainly build one and get it to work (provided the base drive timing assured full energy transfer at min cranking voltage and didn't fry things at max), but I don't think it's the way people would do this in production.
I can't believe you are so confused, John. You are TOTALLY out-to-lunch on this one.
From a previous post...
"Turning ON the transistor does two things... dumps the capacitor through the ignition coil primary (firing the plug) and begins charging L1.
When the L1 current reaches 5A a control circuit (not shown) turns off the transistor, which dumps the L1 energy into the capacitor.
Next point opening, or star wheel control signal, turns on the transistor, repeating the cycle."
Did you miss the part where a "control circuit" turns the device off when 5A is attained? The current is MEASURED!
The device WAS made in production quantities. What is it you think made it not mass-producible?
(Maybe you missing the point that the control circuit is not shown, but it's an integrated circuit with bandgap, smarts, etc. I think you're also missing the point that the capacitor gets discharged completely each firing cycle.)
Other folk had no trouble understanding it ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Easy - increase the pulse width while cranking. Actually, SPICE shows it very well!
[...]
4V while cranking? I think battery specs are a bit higher. And regular ignition systems would also run into problems.
Anyway, there's lots of time to charge the coil while cranking. Jim apparently had no problems. Of course, Arizona winter is mild compared to Canada:)
Jim said the coil cost a buck. Fairchild has inexpensive IGBT transistors for auto ignitions for less than a buck. The cap may cost a buck. Three dollars and change.
The regular Kettering ignition also needs a coil and transistor, so the price increment may be only one dollar for the cap.
Jim's design is ideal for older cars with a weak ignition, which is the market for CD ignition systems. These may cost perhaps $50 for a cheap one to $500 for a high end. Here's one for $120:
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Jim's design would also be useful in triggers for high power strobes, boat engines, maybe even in auto engines used for aircraft where spark energy, weight and reliability are crucial. Providing the energy needed for ignition with a single inductor, a cap and three diodes is a tremendous improvement over the weight and complexity of conventional cd ignition.
Carmakers seem to be moving to coil-on-plug which have individual ignition coils for each plug or pair of plugs. This eliminates the high voltage harness, and provides greater charging time for the coil which increases the spark energy:
Golly, no wonder my car clock loses time on a real cold winter morning:)
So the voltage drop of the extra diode in series with the collector becomes more significant?
Automotive has tough specs.
I flew from St. Paul, Minn. to Phoenix one winter. St. Paul was something like -30F, Phoenix was something like +120F. I still remember the heat shock:)
Gosh, Jim, you're getting crabby. Of course I understand it; I did point out, somewhere way up above, that the base drive width had to be adaptive, perhaps with current sensing, to keep the energy per zap constant.
Your insistance that I don't understand how it works is surprising.
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