Part of Lesson Plan: **Ingredient 3: Ignition (updated) by Thomas Dougherty

Activity Overview / Details

In the secondary ignition section, we will discuss the fact that the theory of operation is the same as in the primary ignition system, but on a much larger scale.  Instead of using a permanent magnet to stimulate electron movement, we will be using an electromagnet which is turned on and off by the ignition module using the primary signal.  We will compare a point controlled distributor to an electronic ignition distributor so the students can see the ignition coil being turned on and off.  We will then discuss transistor function and the fact that a transistor is just a switch with no moving parts.  I will explain that an ignition system needs to produce 8,000 to 10,ooo volts to idle and that some ignition systems are producing 40,000 to 60,000 volts under load.  How do we get that from 12 volts?  A step up transformer!  Using a white board, calculators and Ohm's law (which we are acquainted with from our electrical section!), we will compare the 1 ohm resistance of the primary side to the 5,000 ohm resistance of the secondary side and determine that 12 volts can easily be transformed into 60,000 volts with about 14 amps of current flow.  Enough math, let's go look at it on the scope!