Re: How do Atom Computer Ignition modules work?

[rvpapasso]

Since no one has answered how the Atom modules work I will give the non-technical explanation. With the traditional points and condenser system the points are mechanically opened when the current thru the magneto primary winding is at peak. This occurs when the flywheel magnets pass by the magneto laminations. At that unique time the points open which starts the energy transfer from the primary winding to the secondary winding to make a spark.

The Atom modules do the same with transistor circuitry. There are two circuits, one acts like points and the other is the trigger. The points circuit holds the coil primary to ground the same as the points do. The trigger circuit senses current thru the coil primary. When the trigger circuit senses peak primary current it tells the points circuit to release the primary from ground, the same as the points opening. When all the energy in the magneto is dissipated the circuits reset until the next cycle.

There are many advantages to using the Atom modules instead of points and condenser:

1) there are no contacts to pit
2) the spark is hotter since there are no energy losses due to a condenser and lack of a condenser also allows a faster decay of energy in the primary resulting in a higher secondary voltage
3) no moving parts so there is no wear
4) no adjustment required

There are some disadvantages:

1) timing can not be adjusted since the modules are not adjustable. For the average outboard you will not notice the difference and probably will notice an improvement in starting, idle and smoother top end. Given the wobble in the magneto plate on an old motor that causes excessive point bounce the modules will improve timing.

2) the modules create a spark based on the flywheel magnets passing by the magnetos. If the flywheel loses its timing in relationship to the crank there will still be a spark. This can damage an engine if the flywheel slips on the taper by creating a spark at the wrong time. Point systems do not have this problem since the point timing is directly from the crank.

I have been using the Atom modules for close to close to 20 years on my 1960 40hp Johnson and 18 years on my son’s 1967 33Hp Johnson with no failures or problems. Both engines run great and I noticed no degrade in performance when switching from points/condensers to the Atom modules. I also have used them on other OMC big twins and even a Cushman scooter with a 9Hp OMC OHV engine.