Greetings, Happy new year!
I've been reviewing this thread and realized I didn't include the flipper circuit!
First it is important to understand why pinball manufacturers designed them the way they did.
Use of the solenoid seems to be the obvious choice... But the flipper needs to deliver enough power to oppose the pinball and that is the problem with using solenoids.
Solenoids by nature deliver far less torque when the plunger is extended out of it, versus a plunger retracted within the solenoid.
Below is an animation explaining the theory:
The flipper is a player operated device and needs to be able to withstand being held on for long periods of time. The continuous duty solenoid does not deliver adequate torque in a game. It will be a weak flipper. Below is an example of the result:
Why not just use a very large and powerful solenoid?
We can beef-up the solenoid to a higher current type but they are designed for intermittent use and will quickly heat up and burn out if left on for only a few seconds.
A solution is to use a solenoid which contains two coils in one. The first coil being a high current type which is used to deliver enough torque to the flipper. The second coil is of relatively lower power and used exclusively to hold the flipper on until the player releases it.
The player pushes the flipper button, turning on the high current coil but the high current is only used for a very short time. The EOS switch opens to reduce the current flowing through the coils.
This End Of Stroke switch is much different than previously discussed. It's different than those used in score reel and bumpers, for example.
When the flipper is relaxed, the EOS switch bypasses (shorts across) the hold-in coil. When the flipper button is pressed, it forces full current through the heavy pull-in coil. Once the flipper is nearly full-stroke, the EOS switch opens which allows current to flow through both coils. Since the hold-in coil is of lighter gauge wire (and longer) than the pull-in coil, the hold-in coil will do most of the work.
See the animation below:
Sometimes there is confusion where to connect the EOS switch.
It will -always- go across both sides of the thinner hold-in coil.
Great. The flipper coil has 3 connections. How do I know which is which?
The pull-in coil will almost always be of a thicker, larger gauge wire than the hold-in coil. You can look at the end of the coil itself and usually identify which is which. If there's doubt then a quick check across both coils with a meter will positively identify them. The pull-in will have less resistance. The hold-in will have more.
The Common connection will have an end of both coils soldered to it; One thick and one thinner coil wire.
These will be the connections for the graphic below:
P Pull in coil
C Common (One end of both coils will be connected to this same lug)
H Hold in coil
The EOS switch must open when the flipper solenoid is nearly full-in. That will deliver the most power on the flipper. Warning! it is imperative the switch will positively open upon full stroke. A burned out coil/smoke will result if the switch fails to open.
It is normal for a flipper to buzz, but it shouldn't sound like a 1960's alarm clock.
If it is excessively noisy then check for loose mounting parts or a worn-out copper alloy plunger stop, or a bad plunger.
That's about it for now.