First Project - Servo/Motor Rotation & Reset

Hi folks,

I won't sugar coat it. I am new to this game. However, I'm excited to learn and share. Some background on me;

-Graduated from Electronics Engineering Technician - Digital. -Taught myself HTML, CSS and a bit of JavaScript. -I enjoy tinkering with basic electronics.

For my first project I am trying to make a modification to a pinball machine. I want to take a model F-14 jet that has collapsible wings and incorporated in onto the playfield. Here's the very basics of the mod I want to make;

The Project Basics 1) Initially, the F-14 will have it's wings open. 2) When multiball is ready/running , the F-14 will have wings closed. 3) When multiball has finished, the F-14 will go back to it's initial state with wings open.

To do this, I think the easiest way will be to use a motor or servo. I'll connect the motor/servo mechanically to the wings of the jet to control the open/close movements.

How it should work 1) When multiball is ready specific lamps on the playfield become lit. My plan is to tap into these lamps to power the circuit. 2) When the circuit is provided power (or there is an increase in current) I need the motor/server to rotate 45 degrees (give or take). 3) When the circuit loses power (or there is a decrease in current) I need the motor/server to return to it's start position.

That's the entire mod. It sounds simple, but I don't know if it really is. I've checked out a few video's on how to move a servo, but haven't found any that explain how to reset the servo to starting positions. I think this mod is very possible to do, i just need help.

So I need your thoughts. Is this possible? Would you use a servo or a motor? Am I crazy? :)

Measure the voltage on the lamp when ON and OFF. If that voltage is close to 0 when off and between 3V and 5V when on you can connect it directly to a digital input pin. If the on voltage is low (< 3V) you could use an analog input pin. If the voltae is above 5V you will need a voltage divider to bring it down to the 3-5V range.

A servo wil be your best bet for moving between two adjustable positions. You may find that separate servos for the two wings might make the mechanics easier.

Servo it is. I had not though of using two servos. I would like to keep the cost down so I only ever considered one.

I will measure the voltage tonight when I get home. However, if it's similar to most pins the voltage will be 0V when off and 6.3V when ON. Again I will confirm these numbers tonight. Assuming these numbers are correct and I can use a voltage regulator to bring the voltage down to 3-5V range do you think this is possible to do?

You don't need a regulator (assuming the 6.3V is reasonably stable), just a voltage divider (two resistors). You want about 75% of the voltage (4.7V) to go to the Arduino input pin so you want 1*X Ohms from the voltage source (bulb) to the Arduino pin and 3*X Ohms between the Arduino pin and Ground. The value X should be between about 10,000 and 25,000.

You may run into a problem if it is the Ground side of the bulb that is switched. That should be OK but will reverse the logic: when the bulb is ON (grounded) the voltage will be 0. When the bulb is OFF the voltage through the bulb will be close to 6.3.

I took some measurements with my DMM tonight. The spot I originally hoped to tap power from and trigger the mod to open it's wings will not work. When you power on the pinball machine it goes into "attract" mode. Basically every light on the playfield starts to dance luring people to play the game. This would mean the F-14 would be opening and closing it's wings constantly before anyone even presses START to begin a game. However the voltage was steady in this area. There are 3 contacts. 8~10V, 10V, and 15V.

None of that matters though because there is a 4.8V source I can tap off the coin door to power the Arduino, but I think I'm jumping too far ahead...

I've seen many tutorials on SWEEP for servo's. However, I haven't found any on "zeroing" a servo at power up and then moving the servo to a set position (when triggered) and then moving it back to it's "zero" point (when triggered). I figure this needs to be my first step so I'm going to play around with it a bit but would appreciate any advice. It's basically a SWEEP with trigger points.

There is a good chance that the lamp behaves differently during “attract mode” and during game play. If attract mode blinks the light and game play doesn’t you can use the timing difference to detect the mode. Just a matter of programming.

In attract mode the light blinks sporadically. It has different lighting chase sequences it goes through. The specific light I'm looking at is labelled RELEASE. I will double-check, but I believe it lights up solid when multiball mode is ready to be activated. Once activated there is a unique pattern of sound/music that is played to prep the player for what is about to come. I'm not sure if an Arduino is capable of using a sound queue to trigger the servo. Sound is just an analog signal so it should be possible. I will post some code tonight.

One other issue that I'll hit down the road is that the RELEASE light turns off as soon as multiball is triggered. This means I need to find another trigger that will reset the servo to its "zero" point after completion of multiball. Do you think it's possible to use the ball trough to trigger the reset? The game has a 4 ball multiball. So after 3 balls drain, multiball ends. Each time a ball drains a solenoid activates and pushes the drained ball into the ball trough. So I could use a 3 count. I think these suckers use quite a bit of power though.