A Pinball Clock With ESP8266

I bought my first electromechanical pinball machine when I was 20 years old, and I've had my 1964 Bally Big Day for about 45 years now.

To do something in Corona time I tried to build a similar pinball clock.

I was also very interested in programming an ESP8266 and I started with programming simple light switches (I used a small ESP01). Later I made a matrix clock with an ESP12F and at that time, I saw a, in my opinion, too difficult design of a pinball clock from Elector (1-03-2019), and thought this could be simplified by using the existing switches on the score reels.

Williams 4 digit scoring reel

ESP8266 board with relays or with solid state N-MOS FET drivers

At this point I bought a Williams 4 digit scoring reel assembly.

Resetting the reels to 0000 is done in up to 9 steps via the existing "0" break switches for each digit.

To set the time I used a single minute pulse with overflow to the next digits via the "9" switches (available at the first three digits).

My first design has a few flaws: the maximum current needed from the 24 Volt power supply is to power all 4 reels simultaneously (ca 12 Ampère max: on reset and on digit overflow).

The next issue is to set the correct time after reset. This is done by moving the minute reel step by step. I noticed that setting the correct time took too long. Also, a transition from XX:59 to XX+1:00 was taking 41 minute steps. With 4 steps per second, this took 10 seconds each hour.

The next improvement was to replace the cheap relays on my development Board. I noticed that the current was far too high for the onboard relays, so I replaced them with solid state N-MOS FET drivers that can handle a maximum current of 70A. This is enough to power all coil magnets, even at the same time.

In the appended ino file, the Pinball Clock sketch has the following characteristics:

A WiFi manager for setting a username/password for each WiFi Access Point (with a browser connected to the internal Pinball AP for initial configuration. The internal Pinball AP will start if no WiFi found).

A NTP server to synchronize the pinball clock. This NTP time takes care of time zones and daylight-saving time and adjusts the correct time on the reels.

If no WiFi or NTP server is available, the clock is still usable: the internal ESP clock is used to move the reels every minute (less accurate).

Clock modes: 12H / 24H mode and silent mode.

With a solid-state driver, you can use PWM to reduce the current to the solenoids.

(With relay drivers the End of Stroke switch can be used to add a resistor in series with the reel coils to reduce the current. Note the absence of EoS at the fourth reel.

If you use relay drivers don’t forget to add a snubber circuit to extend the life of the relay contacts.).

I adapted the pinball playfield glass to be used in a pinball clock. I copied a small part of the glass, removed the player indicator, added “Pinball clock”, and ordered this design on 3mm plexiglass. Transparent printing was not possible, so I removed the ink at the four reel-squares. Note the difference between the Bally and Williams reel spacing.

Last step is to assemble the score reels in a mini-Pinball head, connect the drivers/ESP8266 and start the clock.