I want to try my hands at making a mini homebrew project and am starting this thread to post future updates and get advice.

So, first, what is a "mini" homebrew project? Simply put, the idea is to create a tabletop pinball machine with simple rules, scoring and electronics. Someday, when I retire, I want to try a full homebrew project, but I've only recently gotten into electronics, and my mechanical and carpentry skills (as well as ownership of tools) is severely lacking. However, all this year, I've been teaching myself basic circuitry and Arduino programming. I've made several projects including a game where you duel against an opponent using ultrasonic sensors and led lights, a lighted coffee mug holder that you can adjust the color of and that senses your mug and changes its lighting effects when the mug is on it, a 5x5 LED light cube with programmed modes, etc. I need to find a new project, and I thought that I have learned enough to try putting together a simple pinball machine. As I said, it will be tabletop, but have real flippers, functioning targets, hopefully ramps or wireforms, etc. I will program some simplified code and rules with Arduinos. This will take a while, but I think it will be a really good learning experience, especially as I get more used to assembling and creating things mechanically.

As soon as I make progress, I'll post some updates. But, first, I need advice, and I hope to ask a lot of it here.

Here's my first question: I am hoping to run a set of mini-flippers off of a 12v power supply. Based on some preliminary searching, I think this will work. Keep in mind that I don't need a lot of force as I will only be shooting the balls a short distance, and I plan to use ball bearings somewhere between the size of a standard pinball and a marble. Keeping things at 12v will help me ensure safety, and also enable me to use one power supply for all components, including the arduinos and LEDs. Do you agree that 12v should be sufficient? If so, do you know a source for mini flipper assemblies? Pinballlife.com only seems to have larger assemblies, and it is hard for me to decipher Marco Specialties' website in this regard. My hope is to first get the flippers and hook them up to ensure I have enough force. I'll then take this project to the next steps.

Many thanks in advance for your help!

(Oh, one more thing. I do have a theme in mind, but I think I will wait for a later date to reveal it. )

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Index of updates:

Testing the flipper mechs with different voltages: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice#post-5984596

Code to control flippers: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice#post-5986341

Testing assembled flippers: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice#post-5996978 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice#post-6009773

Theme revealed: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice#post-6010828

VUK prototype: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/2#post-6063446 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/2#post-6065153 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/3#post-6080913

Middle orbit with servo motors: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/3#post-6120934 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/4#post-6196940

Left ramp: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/4#post-6135572 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/4#post-6136862

Right ramp: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/4#post-6148122

General layout and test gameplay: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/4#post-6196754 and https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/5#post-6219627

Revised VUK: https://pinside.com/pinball/forum/topic/my-mini-homebrew-updates-and-advice/page/5#post-6284100

What would happen if I ran 12v through those coils? Are you saying the resistance is so high, I wouldn’t have enough current to move the plunger? I don’t think I need them to be as powerful as the ones in the actual pins they were made for, but I do need them to move.

Just looked up the specs. 8.88 ohms resistance. Supply 12v and get 1.35 amps current. It seems like one of the smaller coils out there. Watching this video at 2:30 makes me think it might work (but this will be an expensive experiment if not):

Well, I just ordered two mini flipper assemblies from Marco. The ones for Stern. Last ones they had. Kind of expensive, so I hope it works. I suppose I could always go with 20v if necessary and then just step down the voltage for the other components, but I hope 12v will be sufficient.

I bought a power drive that is selectable from 12 to 24 volts, so I will be able to do some experimenting.

I had not, but that one looks great. I wish he posted more details about the build.

I was going to use transistors to turn the coils on and off. Does it matter whether the transistor is upstream of the coil or downstream? In other words, does it matter whether the transistor is controlling whether power is connected to the coil or whether the coil is connected to ground? Is one better or preferred than the other?

I have some TIP120 Darlington transistors lying around from when I was learning how to control motors with my Arduino. I'll probably just use those (at least for the prototype) assuming they work ok.

What's the purpose of this? Is it the same as when I was playing around with motors? There, I put a diode from the negative side of the motor to the positive to protect the circuit so when it was switched off, stray current is allowed to dissipate. Same here?

Also, am I correct in assuming that these coils have no polarity:

https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=090-5046-01-nd

So, it doesn't matter which lug goes to power and which goes to the transistor?

Thanks, but I think I want to try this by creating as much of the electronics I can by myself, to test what I’ve learned over the past year and solve problems while I go along. If I ever do a full size home brew, I definitely will use existing systems. Here, I think I can do most of the things I want with an Arduino, or two or three.

I’m more worried about making the mechanics of it work than the electronics.

Happy Thanksgiving everyone!

My flipper mechs arrive tomorrow, and I want to start testing them out. I note that they only have one wire winding, not a separate one for kick and hold like larger flipper mechs.

https://www.marcospecialties.com/pinball-parts/500-7019-00

Do I need to worry about them burning out if I hold the flippers, keep them engaged? Do I need to PWM them with an Arduino once they kick?

Or will the voltage be so low for these little mechs that I needn’t worry?

Thanks. By any chance, do you know what the standard is for how much to PWM?

I love parts deliveries:

IMG_1595 (resized).JPG

Having now received my flipper mechs, I was able to test one out. The below video shows me testing it at 12V, 20V and 24V. When I first did it, I thought 12V was significantly weaker than the other two. However, when I took the video, the difference is less noticeable. I think I need to attach it to wood and try to hit a ball with it to see. I have both 11mm (Pachinko) balls and 3/4" balls to try. However, the wood I bought for the playfield (a large piece of particle board) is 1/2" wide, and the mech won't fit on it. I wonder if Stern uses a slightly smaller size. So, back to Home Depot to get the 1/4" version. Also, I'm missing a small roll pin on one of the mechs so can't assemble it fully. I've written to the supplier and hope they can send me one as my local hardware stores don't have them. I'm still really hoping that I can keep this at 12V for a number of reasons, one of which is it will likely mean that I can keep my existing power supply and don't need to buy a larger one with more current, but we'll see.

I hate assembling stuff sometimes. One screw’s head fell off. The other one won’t go down all the way. And, this was the last bracket in stock for the left mini flipper. Luckily I think it is on well enough to function. Not sure I’ll be replacing the coil any time soon though.

C46B75B8-CB72-42BC-B531-67AFBD692A91 (resized).jpegC993656E-61EE-455A-8E7C-9B5ACEE92070 (resized).jpeg

My friend helped me cut the cabinet and playfield wood out of fiber board with his table saw.

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Waiting for parts today to complete the second flipper assembly and to assemble the cabinet. Home Depot never has the right size screw that I need for pinball. It is always one size lower than their lowest size. So, I'll try one of the few Ace Hardwares in my area when they open tomorrow.

In the meantime, I decided to write a little sketch to control the flippers with the Arduino. I haven't tested this yet, so there may be bugs in it, but the idea is to apply high power to the flippers for X milliseconds and then apply lower power through pulse-width modulation after that. I have two variables that I can play with to optimize the control -- HighKickTime controls how long the flipper receives high power, and PWM controls the amount of reduced power after the high kick time, with 0 being no power and 255 being full power. So, when I get my flippers hooked up, I can experiment with different values for both as well as the voltage going to the flippers themselves.

I'll post code for anyone interested. However, please keep in mind that this is untested at this time and may have bugs. If I discover any, I'll post and update the code.

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// Flipper control with PWM

#define RightFlipper 9 // Pins for PWM to the transistors
#define LeftFlipper 10

#define RightButton 7 // Pins for receiving input from the buttons
#define LeftButton 8

int PWM = 100; // How much to PWM? Value can go between 0-255.
int HighKickTime = 200; // Time to apply high power to flipper to get the initial kick.

boolean FirstPushRight = false; // Variable to keep track of when you first push a button.
boolean FirstPushLeft = false;

unsigned long StartRight, CurrentRight, ElapsedRight; // Variables to keep track of how long a button is depressed.
unsigned long StartLeft, CurrentLeft, ElapsedLeft;

void setup() {

pinMode(RightButton, INPUT);
pinMode(LeftButton, INPUT);
pinMode(RightFlipper, OUTPUT);
pinMode(LeftFlipper, OUTPUT);

}

void CheckRightFlipper() {

if (digitalRead(RightButton) == HIGH) { // Right flipper button is depressed.

if (FirstPushRight == false) { // First time the button is pushed, start timer.
StartRight = millis(); // Start timer by recording time button is pushed.
FirstPushRight = true; // Keep track that button is pushed so as to not repeat this step.
analogWrite(RightFlipper, 255); // Full power to do the initial kick.
}

if (FirstPushRight == true) { // Button has already been pushed. Now measure elapsed time.
CurrentRight = millis(); // Check current time.
ElapsedRight = CurrentRight - StartRight; // Calculate elapsed time for how long the button has been pushed.
}

if (ElapsedRight >= HighKickTime) { // If time elapsed exceeds the time for the initial high voltage kick, then start PWMing the signal to the flipper.
analogWrite(RightFlipper, PWM);
}

}

if (digitalRead(RightButton) == LOW) { // Right flipper button not depressed or has been released.
FirstPushRight = false; // Reset variable.
analogWrite(RightFlipper, 0); // Turn off signal to flipper.
}

}

void CheckLeftFlipper() {

if (digitalRead(LeftButton) == HIGH) { // Left flipper button is depressed.

if (FirstPushLeft == false) { // First time the button is pushed, start timer.
StartLeft = millis(); // Start timer by recording time button is pushed.
FirstPushLeft = true; // Keep track that button is pushed so as to not repeat this step.
analogWrite(LeftFlipper, 255); // Full power to do the initial kick.
}

if (FirstPushLeft == true) { // Button has already been pushed. Now measure elapsed time.
CurrentLeft = millis(); // Check current time.
ElapsedLeft = CurrentLeft - StartLeft; // Calculate elapsed time for how long the button has been pushed.
}

if (ElapsedLeft >= HighKickTime) { // If time elapsed exceeds the time for the initial high voltage kick, then start PWMing the signal to the flipper.
analogWrite(LeftFlipper, PWM);
}

}

if (digitalRead(LeftButton) == LOW) { // Left flipper button not depressed or has been released.
FirstPushLeft = false; // Reset variable.
analogWrite(LeftFlipper, 0); // Turn off signal to flipper.
}

}

void loop() {

CheckRightFlipper();
CheckLeftFlipper();

}

Changed HighKickTime variable to 50 and PWM variable to 75. (5 Dec 2020)

Changed high kick time to 60. (12-12-20)

Thanks for the tip. I guess I’ll try starting there and see how it goes.

Ugh. I already see bugs in my code. Stupid double equal signs gets me every time.

Thank goodness for Ace Hardware. They have the types of screws Home Depot doesn’t bother to carry. It allowed me to create my cabinet. I even found a roll pin to allow me to complete my left flipper assembly.

The cabinet is held together by metal brackets. The playfield sits on top of the brackets. I can easily remove it to work on the playfield and then put it back in. If this all works out, I’ll try to make something more permanent, but this is good for my “white wood”.

My first attempt to get a 6.5 degree pitch didn’t really work out. My second attempt was a lot closer, and I can easily dial it in with some rubber feet.

B90B90FC-219E-4E3E-8F66-FCEEB4617445 (resized).jpegE3CD0B13-681E-48E1-8FC1-115E09FB5070 (resized).jpeg

Rainy day making boards and soldering.

AA15896D-D94C-4D98-A16A-E583D26CFADF (resized).jpeg

Here's my first test of the flippers:

20 Volts seems to be the magic number. The right flipper seems a bit weaker than the left, and I'm not entirely sure why. The left will work a bit more at lower voltages, while the right has trouble. And, the right seems a little weak when I hit the ball from the cradle position (i.e., when it has been held up, released, and then hit quickly again).

The right has an older flipper coil labeled from Stern on it. It was in the kit I got and it seemed a bit old. The left has a brand new looking generic coil from Marco. It could also be a bad solder joint. I'm not sure. I want to get things set up a bit more, and then I'll really be able to tell. I'll take some videos of it hitting the ball when I do. Right now, the flippers hit the ball (which is .75" in diameter) fairly hard, and it easily thumps against the top of the cabinet. I expect it will go up ramps no problem.

I've used Schottky diodes across the flipper coils. Not sure that was necessary, but since I'm PWMing the hold signal, I thought it couldn't hurt. Right now, I'm PWMing at 75/255. It seems plenty powerful and holds well at that level. That's assuming my code is actually working correctly. I think I'll try dropping it lower to see.

Finished my flipper control boards and attached them to a scrap piece of wood just to get everything organized. Put a buck converter on there as well which steps down the voltage from 24V to 5V to control the logic circuits. Also hooked up flipper buttons on the side of the pinball cabinet.

IMG_1623 (resized).JPG

I settled on 24V to the flippers. I apply full power for 60ms and then PWM at a duty rate of 75/255. I played around with other values, but this seems to be the sweet spot. At that PWM rate, it takes a lot of force for me to try to lower the flipper when it is held up, and the ball coming at it at normal speed, won't send it down. At lower rates, I could easily push the flipper down when activated, and the ball could also lower the flipper.

Here's a video of me testing the flippers at these settings (I added some foam board return rails just to keep things moving for now):

At first, I was a little disappointed in the force the flippers applied. They would hit the ball pretty hard straight up or with a back hand. But, if I tried to hit the ball to the other side of the table by hitting it more with the tip of the flipper, it would be a very weak hit. It would never make an orbit or ramp. I tried lowering the pitch of my flippers so that I could aim for the opposite side of the table higher up on the flipper, and that seems to have helped significantly.

Right now, I'm using a 3/4" ball. I like the size, but if I use a 5/8" ball, I can hit it with more force, it will be more in line with the scale of the table, and I can probably have a bit more space to play with on the table in terms of lanes, ramps, etc. I have some 5/8" balls coming Monday to see how they feel. One issue with going lower in size is that all the rubber rings, targets and stuff that I eventually plan to put on the table will likely have to be that much lower to the playfield itself. I also am not sure if the ball will have enough mass to trigger stand up targets if I buy standard ones. Ball size is going to dictate layout and other stuff, so I need to make a decision eventually. Next step will be to add some test ramps, orbits and stuff to start testing the layout. So maybe I'll just see how it goes and play it by ear.

It might be time to reveal the theme I have in mind. Anyone able to guess?

BathHouse (resized).jpg

Yeah, I did. I lengthened it all the way to 200. No better.

Also, I don’t know if you noticed the whine from the flippers in my video. Is that normal? It is pretty loud in person.

For the win!

Spirited Away is one of my favorite movies. So much amazing and rich content in it. I have some ideas for how to incorporate some of it in the pin. We’ll see how practical those idea are when working at this size and also how well I’m able to do any of it. For instance, I would love to be able to do a recreation of the bath house in my picture on the back of the playfield, but I have a long ways to go before I can start figuring that part out.

My 5/8" balls arrived today. I definitely get better hits off the tip of the flipper and to the side of the table with the smaller diameter. However, when I hit them straight up the playfield, they fly. I'm worried about airballs. Unfortunately, it just seems like there is going to have to be a tradeoff here. I'm going to start building a playfield layout around the 5/8" balls first and see how that goes. The balls are more in keeping with the scale of the table overall.

I didn't realize this when I bought the mini flipper assemblies that are used for Munsters, Family Guy, etc., but the Munsters sub-playfield actually uses the 5/8" balls. I've been watching some videos, and those balls fly around. But that playfield is more compact and seems designed for it. I'll just have to see how things go.

So, onto something I'm not very familiar with, and that is prototyping the layout itself. I have lots of cardboard from Amazon boxes to try to make ball guides, ramps, etc., just to try certain things out. zacaj , I've also been skimming your own homebrew thread. Looks impressive. I saw that you started experimenting with Future Pinball to design a layout. I haven't read through the whole thread, but was that useful? I downloaded it and started playing around, but there is a bit of a learning curve. I might be better off just trying things by hand.

Not standard mechs, but everything will retain roughly the same scale as a normal table, just 50% smaller. I just want to get a feel for how to fit things around each other, which it may allow me to do.

Looking a little more like a pinball machine.

3CF39492-A362-4C5E-B227-1BF99907F22C (resized).jpeg

Time to make a shooter rod.

3C46BA42-8E1E-42D1-BAEB-AF0438DB1099 (resized).jpeg

You have to get creative when working at half the scale. Luckily, Ace Hardware to the rescue again. They have those odd parts that Home Depot just doesn’t, like collar shafts.

9237891B-156B-4191-952C-90E4A5C56A7A (resized).jpeg

It needs to be centered and have some sort of housing on the outside to prevent wiggle, but it works!

I’m getting kind of sick of cutting cardboard and hot gluing stuff together. I thought prototyping the layout would be the fun part, but it is pretty repetitive so far. Still, I’m slowly making progress.

C76A4401-C34B-445D-845A-8AB781CB952D (resized).jpeg