Introducing: Electronic Tilt Bob for Pinball Machines - Part I

I’m excited to announce to the world … the very first Electronic Tilt for Pinball Machines which simulates the movement of a mechanical tilt plumb bob.

It’s a project I’ve been thinking about for a number of years but only got really serious in the past few months. Bench testing is complete and the next stage is to place it in a real machine.

Follow my progress on


Interesting. There were some in the UK pinball scene that talked about this a good number of years ago too, but I don’t think anything came of it there either.

As well as being super easy to re-calibrate after moving the machine to a new location, a system like this might also allow the tilt to immediately stabilise between balls, which would be a good benefit to tournament play, though would probably also need game specific (certainly game era specific) electronics.

Good luck!

1 Like

Glad to know that there is someone else, besides myself, that finds this project interesting … thanks Wizcat for the support.

Another reason for me posting this is to gather more ideas to improve upon and you’ve just mentioned one I hadn’t thought about yet (ie immediate stabilization between balls). Part of my routine is to zero the velocity of the tilt bob when it detects a tilt condition, just as a real bob would when it hits the ring.

Changing from one player to the next presents a different issue. That being, how do we know when the player has changed? There is no ‘common’ signal from all eras of pinball machines that can do this. An external signal would need to trigger this. I could easily do this over WiFi but it’s not automatic. I would rather find a solution where this procedure is invisible to the player.

I don’t think I follow you in regards to ‘game specific’ electronics. Was this in relation to zeroing the tilt between players? The current electronics used to close the tilt were chosen so that it it could replace the tilt bob in any era of machine.

I think the P3 system has something like this already. But a Mod would be nice!
You might as well add leveling and pitch as well.

I have been kicking around trying to do something like this as a cool overlay for live streaming. I think seeing how great players nudge visually, would be awesome.

My only good idea I think I had was that the module should plug into the service outlet, because that is a a consistent, solid mounting point.

1 Like

Thanks for the input Eggman.

To the best of my knowledge, no other product simulates a mechanical tilt bob. I can find examples of others using “Simple Force” (which I’ve also simulated) but nothing simulating the motion of a mechanical tilt bob. Additionally, without a proper six point calibration, the data on these other products is unreliable (ie a 1g force might appear as 0.95g or 1.1g)

Leveling and pitch is something I thought long and hard about. I did include an “Accelerometer Fine Tuning” web page for two reasons. The first was to zero out the values of the accelerometer since no two devices (accelerometers) will have 100% identical outputs. The product datasheet specifically states this so it needed to be accommodated for. The second reason has to do with physical mounting (levelling). As most people would eyeball the setup, it probably isn’t mounted perfectly square. Hence a fine tuning offset would help.

One thing I did consider is mounting of the device at an angle (ie 30 degrees off). I could do the math in the software, but decided against it in the end. You wouldn’t mount a mechanical bob at 30 degrees so chances are you wouldn’t do the same for an electronic version … perhap I’ll address this again in later versions if people ask for it.

gammagoat I appreciate your input … thank you

When I first started this project, I was thinking that people would remove the screws from the old tilt mechanism and mount the electronic version in its place. As time went on, I realized I could mount the device anywhere inside the cabinet (hooray for flexibility). So technically speaking, any solid mounting point would do. [One should also consider Lever Arms when mounting, but that’s probably too in depth at this point in time]

The “Classic (Tilt Bob) Tuning” page actually shows you the bob’s movement in real time. As you bump the machine, the bob will move and settle per the math. Unfortunately, I just showed a static shot in the blog … I’ll try to post a video to the blog in a few days.

I’d like to add that the MQTT server streams the accelerometer data, but not its position (for now). I’m leaning towards MQTT as part of the tournament interface/monitoring since it’s a lightweight communications interface and any heavy lifting can be done by an external PC to collate the data of multiple machines and display it.

I don’t know that you need concern yourself at first with settling the tilt bob for each player or ball, you could simply have that as a button within the control/visualization app.

Sounds awfully complicated to calculate how a tilt bob in motion reacts to a nudge.

This project brings up all kinds of feelings.

We obviously didn’t have it as early as you mention, but we discussed it internally in 2011. We talked about filing a patent but were advised it was unpatentable since all we’re doing is replacing one technology with another to do the same thing.

However, that didn’t stop Multimorphic and Stern from filing patents over it.

The short story is that you can look up the prosecution of Multimorphic via application number 13933590. After like 4 years and at least 2 lawyers, he finally got patent 9,604,129 for it. Now, that doesn’t mean it would hold up to a court challenge since simply replacing a bob with an accelerometer would be considered obvious, but until it gets challenged, technically he has it. The only thing even remotely novel about MM’s application is that he mentioned you could use it to encourage shaking/shoving. Pinball has spent over 100 years trying to avoid abuse, and he’s encouraging it, lol.

The Stern prosecution is a thing of beauty to go over. You can find theirs at application number 13796261. They’ve been rejected and final rejected multiple times, filed the absolutely flimsiest affidavit I have EVER seen, been upheld in rejection by the board of appeals, and have since filed ANOTHER affidavit (now with 400% More Proof) that has been rejected already. If you’re more than a casual patent fan, it’s worth a look.

Now, I get the motivations. Gerry wants to claim something “cool” and “innovative” (lol), and Stern wants to save the $5-6 a plumb bob costs each game (that can be their ONLY motivation for going after MM’s patent so hard).

But pinball machines are noisy. Like, really noisy. Not just coils, but subwoofers too. I haven’t seen a P3 in person yet to know how good their virtual tilt is (honestly, I thought I saw a bob in one, but I can’t find the pic again so maybe I made it up). You’ll find out soon enough, I guess. Good luck, but be wary of the patent since by default you’d lose right now.


On any single ball game you could just link into the outhole kicker.

I don’t think that would be a good idea, generally.


1 Like

That’s mostly a problem on games that don’t advance to the next ball on zero switch hits, though. Gottlieb EMs like Jungle Queen for instance, gives you no such luck.

A tilt-bob with an mcu programmable over wifi. This could make for interesting tournament play :stuck_out_tongue: .

Maybe infosec conventions could be there new tournament venue. Combination pinball and CTF

@ misterschu It’s not that complicated if you understand calculus and physics … however, when it comes to being artistic, let’s just say I have trouble keeping the crayon within the lines.

We all have our individual strengths and weaknesses. Mine just happens to be maths & sciences.

@keefer … thanks for your input. Never realized you were with JJ until I read your profile. Kudos to you and JJ … I like what you’re doing.

I had previously done research on patents as this was initial concern of mine:
5,338,031 - William mechanical tilt bob - granted in 1994
9,604,129 - MM - granted 2017
Pub US2014/0265113 - Stern - filed 2013 - not granted as far as I can tell

I had to laugh at the MM patent as they talk about levelling information from the accelerometer in Yaw, Pitch, Roll … those are rotational components normally obtained via a gyroscope. This tells me that that they are only concerning themselves with using the accelerometer information to calculate how far off level the machine is when first turned on. The machine will not yaw/tilt/roll during play unless you tip it over or spin it around. I’m surprised the patent reviewer didn’t catch this. Perhaps the patent was granted based more on the animated playfield portion and the accelerometer levelling was glossed over. Nothing is mentioned about simulating tilt bob movement with math.

The Stern publication has not been granted and probably never will. They talk about setting a trigger level and when an instantaneous force exceeds this level then cause an alarm(tilt). You know, the exact words from the accelerometer datasheet describing how to use their product in multiple types of applications. Effectively, if I place my smartphone on top of a machine then it infringes their application. I have that feature as a secondary consideration and called it the “Modern (Simple Force)” method. If push came to shove, I’d drop that feature off my design in a heartbeat if they were to actually get the patent granted.

Bottom line … the specific wording in their own patents negates any claim they may have against my design. I believe this is mainly because there was a race to the patent office to file anything in hopes of dissuading competition instead of understanding what to file in the first place. The vagueness of the application details shows the complete lack of scientific knowledge on the subject of how an accelerometer can be used beyond its basic intended functionality to detect a simple force level.

@zacaj et al … thanks for your suggestions. I DO appreciate any input from fellow tilters

I did consider the outhole kicker at one time but decided against it since a multiball machine with a plunger kickout would reset the tilt during the game. Medieval Madness comes to mind as one such machine.

An external reset button is an ugly ‘kluge’ which I would like to avoid.
Using the WiFi connection to reset it is also a bit risky in that anyone could log in and reset it. However, I do have some ideas in regards to using the MQTT server to publish a reset command. That way only the tournament operators would have the ability to reset it.

I’m currently working on a small board to sit between the coin door and the rest of the machine for remote credit/audit purposes (it’ll probably never ship, but I’m having fun). Because of this, I’ve been spending entirely too much time looking at coin door interface board schematics.

Today I was looking into what it might take to support a Spike system, and came across something kinda interesting – the Spike cabinet node board already has an accelerometer on it. Check out the LIS3DH at 3/3F:


Nice catch. Even if someone else has the patent on a digital tilt mech, I can see leveling a game via the display in the very near future.

Seeing too many ops these days jacking up the back legs on games that are designed to be at 6.5 with levelers all the way up. Would be nice if this helped that.

Good eye jrb

Taking a quick look at it, I see they are using the SPI bus to communicate and both the accelerometer’s interrupt pins are mapped out.

One interesting thing I did notice was the digital input for “plumb tilt” (location 3/4/C & 3/8/C). It makes me wonder what the accelerometer is actually used for … or if it is designed for ‘future use’