Mike's models: Pinball machine

Back in 2016 I decided to build a pinball machine but could not get the scoring circuit to work, so abandoned the project.

After building unique models in bottles, I needed a long term project, so I revisited the pinball machine.

This is the initial general layout but will probably change as I progress and find alternative options.

I decided to get all the various light circuits and mechanical modules to work, before building the playfield itself.

I finally got the scoring circuit to work.

For the sound circuit, I found a circuit on YouTube that suited me.

Prototype “score control board”.

Next was to design the rollover switch that would provide a pulse when the ball rolled over it.

I got a pack of 20 micro switches from Takealot and modified them by gluing a length of stainless steel wire to them with 5 minute epoxy and shaping them as shown. The brackets were made from pvc electrical wall boxes.

Now to connect the switches to “playfield switch termination boards”.

These boards would connect the inputs from the switches to the “score control board", and LEDs if required.

Playfield boards sequence chart.

“Playfield switch termination boards”

Each input to this board will give a pulse to the score board and also operate the relevant LED.

Each input to this board will give a pulse to the score board.

After a few weeks of breadboarding various chaser circuits, I finally settled on this one.

This is the prototype proof of concept.

This is the final version of the LED driver board,

and the LED cluster.

This will go in the centre of the playfield.

I now made the final versions of the score control circuits.

The 7 segment display board was mounted in a scrap piece of 3mm plastic.

The mountings were made from 4mm countersunk machine crews, superglued to the plastic and then a fillet of baking soda and superglue made a permanent anchor for them.

The next circuit to create was a one-shot sequence LED chaser circuit for each of the top 5 ball lanes. When the ball enters one of the 5 start lanes, it will go over the corresponding rollover switch and energise the set of LEDs in a one-shot sequence.

Here is the final working circuit.

and here it is working.

That’s the main electronics sorted, now to start on some of the mechanical elements.

The ball plunger.

This was made from a length of 12mm hardwood dowel, a door knob, some washers, 13mm ID aluminium tube and a spring from a plunge router. The end of the rod was capped with a rubber stopper and using a Dremel cutting disc, a groove was cut into the rod behind the stopper to take a circlip which would retain the spring and washer.

Next are the flipper mechanisms.

I built a prototype jig to test the linkages and operation. This is where you correct all your mistakes and create the template for the final version on the playfield.

The flippers were made from wood and grooves routed front and back to hold the rubbers made from “O” ring rubber cut to length and glued with cyanoacrylate (superglue).

The mounting shafts were made from cup bolts, modified as shown.

The slingshots.

The rubber mounting pillars were made from plastic nail-in anchors.

These comprised of a shaft and 2 anchor heads, cut to size.

After a lot of trial and error, I finally got a mechanical layout for the ball return that works.

I am trying to do as much as I can mechanically and keep electrical operation to the minimum in order to simplify repairs if necessary.

I now started to build the playfield.

This is the ball return mechanism.

After a week of experimenting with various rubber bumper positions, I finally decided on this layout.

Now to make the springsets which fit behind the bumper and slingshot rubbers and increment the score when operated. They will also operate a circuit which will give an audible tone.

I had a coil of 1,2mm stainless steel wire and the “spring sets” were made from this. The spring set mounting blocks were made from a load of plastic shelf support blocks that I had spare.