Ignition updates to the Unofficial FAQ

Page 3 of 3  


The emitter is the neutral part of it, the part the collector gets switched to.
Maybe the easiest way to think of it is as a relay, where the emitter is one end of the winding and one of the contacts. The base is the other end of the winding and the collector is the other normally open contact. When current is run through the "winding" (from the base to the emitter) the collector closes the circuit to the emitter.
There are a few technical details like polarity (the collector and base both have to be positive with respect to the emitter) and the base resistance (so low the current has to be limited by external resistance), but the operation in an ignitor is just like a very fast relay. In other circuits it isn't used as a relay, and the collector current is varied more proportionately to the base current.
Mike
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Most materials have an electron flow, which goes from negative to positive. I've heard that some materials can have a proton flow. Both may exist in a vacuum.
Current flow arrows on diagrams go from positive to negative.
Bipolar transistors are current amplifiers. When a current flows through the base-emitter diode junction, a stronger current is allowed to flow from the collector to the emitter. The C-E junction is .2 to .4 volts when the B-E junction is saturated (~.65 V). The current gain for a power transistor is usually 10 to 100. Darlington pairs have that gain squared. Gains are not at all consistent so they're usually specified as a range.
MOSFETs are tiny voltage controlled amplifiers. Absolutely zero static current is required to turn them on or off; just the capacitance current. Because of their infinite current gain, millions may be paralleled on a single chip to satisfy any current load. Their voltage gain is very low - a typical gate threshold voltage is 4V and a typical gate saturation voltage is 10V. There's no voltage drop between the source and drain, only resistance. High voltage capability makes each MOSFET junction larger and dramatically increases resistance.
IGBTs are similar to bipolar transistors but with an insulated gate like a MOSFET. They have the high voltage capacity of bipolars but need no driving current like a MOSFET. They're very slow so they're usually limited to controlling industrial motors. (Honda hybrid cars use them for their motors.)

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wrote:

So then my diagrams are correct. I assumed the base electrode to act as the switch, turning power on and off between the collector and the emitter.
Thanks.
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TeGGeR

The Unofficial Honda/Acura FAQ
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Kevin McMurtrie wrote:

don't get no proton flow unless you're into nuclear chemistry. in semiconductors, conduction is by way of negative electrons & positive "holes". you /can/ have [positive] ions move in the semiconductor lattice, but they are not a part of the primary conduction mechanism & result in mass transport & therefore degradation of the semiconductor - they are not a proton thing.

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Here are oscilloscope traces of an ignition coil with and without a capacitor:
http://www.pixelmemory.us/Photos/Nerd/flyback /
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Kevin McMurtrie wrote:

awesome! that one without capacitor is /real/ ugly...
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It reminds me of my Mazda rotary with points. I could see the dwell begin to take up too much time as the RPM got higher.
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Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
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snipped-for-privacy@XReXXIgnit.usenet.us.com wrote in wrote:

I had a '74 RX-4 Coupe!

You guys...I swear...
If the subject gets any more high-flown, it's gonna head for outer space.
This is excellent info. Now I've got to make another page: More detail for the Electronics Whiz.
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TeGGeR

The Unofficial Honda/Acura FAQ
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