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Coil-fired plungers / ball launchers

Related Config File Sections:

Many modern pinball machines use some kind of "launch" button to launch the ball into play.

Sometimes these look more-or-less like traditional plunger lanes, except there's a solenoid instead of a spring-powered plunger, like this:

image

Other times these are more like "catapult" devices with a coil attached to the arm to launch the ball into play:

image

Note that if you have a coil-fired ball launcher that's combined with a spring plunger (giving the option for manual spring launches or machine-controlled auto launches, stop here and follow the /mechs/playfields/ball_tracking guide instead.

1. Add the switches

The first step is to add your plunger's switches to the switches: section of your machine config file. Create an entry in the switches: section for both the switch in the device that's active when a ball is sitting in the plunger ready to be launched, and also create the entry for the switch connected to the button the player hits to launch the ball.

Here's an example:

switches:
  s_plunger_lane:
    number: 2-6
  s_launch_button:
    number: 1-5

Note that we configured this switches with numbers 2-6 and 1-5, but you should use the actual switch numbers for your control system that the switches are connected to. (See How to configure "number:" settings for instructions for each type of control system.)

Be sure to set the type: NC if either of these switches is an opto and to configure the other switch settings as needed.

2. Add the coil

Next, create an entry in your coils: section of your machine config file for your plunger's eject coil. Again, the name doesn't matter. We'll call this c_plunger and enter it like this:

coils:
  c_plunger:
    number: 2-1
    default_pulse_ms: 20

Again, the number: entries in your config will vary depending on your actual hardware, and again, you can pick whatever name you want for your coil.

You'll also note that we went ahead and entered a default_pulse_ms: value of 20 which will override the default pulse time of 10ms. It's hard to say at this point what value you'll actually need. You can always adjust this at any time. You can play with the exact values in a bit once we finish getting everything set up.

3. Add your plunger / launcher ball device

Remember a ball device is anything in your pinball machine that holds a ball (even if it's just for a short time). So your plunger lane / ball launcher is a ball device.

In this case, you can add an entry for your plunger to the ball_devices: section of your machine-wide config, and then create sub entries for the ball switch and eject coil.

Here's an example. Note that in this case, we've left out the other ball devices (such as your trough and/or drain):

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
ball_devices:
  bd_plunger:
    ball_switches: s_plunger_lane
    eject_coil: c_plunger

In the example above, we named the plunger device bd_plunger, but if course you can name it whatever you want. You might use bd_catapult for a catapult-style launcher, or bd_right_plunger and bd_left_plunger for a game like Judge Dredd that has plunger lanes on both sides.

Note that the ball_switches: entry will just be a single switch. It's the switch that's active when a ball is sitting in the plunger waiting to be launched. (This is NOT the switch the player hits to launch the ball.)

Since there's only one switch listed in the ball_switches: section, that will tell MPF that this device can hold one ball.

4. Configure the launch switch

Next you need to configure the plunger lane so it launches the ball when the player hits the launch button. In MPF terms, this is technically the plunger "ejecting" the ball, so we use a setting called player_controlled_eject_event: which you add to your plunger.

At this point, you might be wondering why we configure a player controlled eject "event". Why is it an "event" and not a "switch"?

This is due to MPF's flexibility to support the myriad of different types of machines in the world.

For example, some machines launch the ball when a player hits a button. Others launch it when the player releases a button. Still others play a little show then launch. Etc.

So we decided, "Hey, we have this great events system in MPF, so let's just use that."

Remember that by default, there are "active" events that are posted when a switch becomes active, and "inactive" events that are posted when a switch that was active becomes inactive.

4.1 Launching the ball when a player hits the launch button

Assuming the switch tied to the launch button (or gun trigger or fishing rod button or whatever you have) is called s_launch_button, then that means an event called s_launch_button_active will be posted as soon as that switch is hit. In that case, you'd configure your plunger like this:

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_launch_button:
#!     number: 2-7
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
ball_devices:
  bd_plunger:
    ball_switches: s_plunger_lane
    eject_coil: c_plunger
    player_controlled_eject_event: s_launch_button_active

Pretty straightforward.

4.2 Launching the ball when a player releases the launch button

If you want to launch the ball into play when the player releases the launch button, then just use that switch's inactive event:

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_launch_button:
#!     number: 2-7
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
ball_devices:
  bd_plunger:
    ball_switches: s_plunger_lane
    eject_coil: c_plunger
    player_controlled_eject_event: s_launch_button_inactive

Note that whenever the player_controlled_eject_event: is used, MPF has to specifically enable the ability for that event to eject a ball. In other words, you don't have to worry about the player hitting that switch to launch extra balls into play, and it's fine if that event is posted in other places in your game.

5. Configure the eject confirmation, target & timeouts

Next you need to configure some settings that will let your plunger know whether ball launch events were successful.

The first setting is called eject_targets:. (You may remember this from when you configured your trough or drain device.) This setting is a list of one (or more, if there's a diverter) ball devices that your plunger lane ejects into.

In probably 99% of cases, the plunger device only ejects to the playfield. In that case you do not need to configure your eject_targets: because the playfield is the default setting.

However, if your plunger lane ejects to some other device (maybe another launcher or a subway or something) other than the playfield, then you'd configure that here.

Next up is the confirm_eject_type: which is how MPF knows that a ball really made it out of the plunger and won't fall back in.

In most cases, the default setting of "target" is fine (because that means that MPF just watches for the target device (from above) to get a ball, and when it does, it assumes the eject from this device was successful.

However, plunger lanes that eject to the playfield sometimes have a switch that's activated when the ball leaves the plunger. You can use this switch with a few caveats:

  • If this switch has been hit, it means the ball is out for sure, and it's not possible for it to roll back.
  • This switch must always be hit, e.g. the ball can't sneak around it.
  • No other balls should be able to hit this switch while they're in play.

What this means is that this switch is pretty limited and almost never used.

Finally, you need to configure the eject_timeouts: which is a time setting for how long MPF will wait to confirm the eject. If a ball re-enters that device before the timeout happens, then MPF assumes the eject failed and will try it again.

For the eject_timeouts:, you want to figure out what the MAXIMUM time is that a ball could be ejected from the plunger but still not make it all the way out and then fall back into the plunger. You'll have to play with this setting in your machine, but in most machines it's probably around 3s.

Here are some examples of these settings in action.

First, for a typical coil-fired plunger lane / catapult that ejects the ball directly to the playfield: (This is probably 99% of all cases)

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
ball_devices:
  bd_plunger:
#!     ball_switches: s_plunger_lane
#!     eject_coil: c_plunger
    # ...
    eject_timeouts: 3s

Next, for a coil-fired plunger that has a switch at the exit of the plunger lane that is only hit if the ball has made it out of the plunger and cannot be hit by a random ball on the playfield:

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_plunger_lane_exit:
#!     number: 2-7
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
ball_devices:
  bd_plunger:
#!     ball_switches: s_plunger_lane
#!     eject_coil: c_plunger
    # ...
    confirm_eject_type: switch
    confirm_eject_switch: s_plunger_lane_exit
    eject_timeouts: 3s

Next, if your plunger lane ejects into another ball device (a cannon, in this case):

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_canon:
#!     number: 3-1
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
#!   c_canon:
#!     number: 2-2
#!     default_pulse_ms: 20
ball_devices:
#!   bd_cannon:
#!     ball_switches: s_canon
#!     eject_coil: c_canon
  bd_plunger:
#!     ball_switches: s_plunger_lane
#!     eject_coil: c_plunger
    # ...
    eject_targets: bd_cannon
    eject_timeouts: 2s

6. Set your trough/drain device eject_targets

Once you have your plunger device set up, you need to go back to your trough or ball drain device and add the new plunger to your trough's eject_targets:, like this:

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_trough1:
#!     number: 3-1
#!   s_trough2:
#!     number: 3-2
#!   s_trough3:
#!     number: 3-3
#!   s_trough4:
#!     number: 3-4
#!   s_trough_jam:
#!     number: 3-5
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
#!   c_trough_eject:
#!     number: 2-2
#!     default_pulse_ms: 20
ball_devices:
  bd_trough:
    ball_switches: s_trough1, s_trough2, s_trough3, s_trough4, s_trough_jam
    eject_coil: c_trough_eject
    tags: trough, home, drain
    jam_switch: s_trough_jam
    eject_coil_jam_pulse: 15ms
    eject_targets: bd_plunger
#!   bd_plunger:
#!     ball_switches: s_plunger_lane
#!     eject_coil: c_plunger

Of course you'd add the name that you gave your plunger device, which could be something like "bd_catapult" or whatever you called it.

Also, if you have a two-stage drain (like a System 11 machine), you'd add this to the second device (the one that feeds the plunger).

7. Add the plunger as default_source_device

Next you need to your plunger lane ball device default_source_device to your playfield to tell MPF that this ball device is used to add a new ball into play.

To do that, add your new plunger ball device as default_source_device in the default playfield, like this:

#! switches:
#!   s_plunger_lane:
#!     number: 2-6
#!   s_plunger_lane_exit:
#!     number: 2-7
#! coils:
#!   c_plunger:
#!     number: 2-1
#!     default_pulse_ms: 20
#! ball_devices:
#!   bd_plunger:
#!     ball_switches: s_plunger_lane
#!     eject_coil: c_plunger
playfields:
  playfield:
    default_source_device: bd_plunger
    tags: default

8. Tag your playfield switches

Since the plunger lane ejects balls to the playfield, it's important that you have your playfield switches tagged properly since that's how MPF knows that a ball is loose on the playfield.

See the How MPF tracks the number of balls on a playfield documentation for details.

Complete config example

Here's a complete machine config with a "standard" coil-fired plunger that ejects the ball directly to the playfield. Note that this config does not include the switches and coils for the trough.

This config is what probably 99% of machines with coil-fired plungers will use:

switches:
  s_plunger_lane:
    number: 2-6
  s_launch_button:
    number: 1-5
  s_trough1:
    number: 3-1
  s_trough2:
    number: 3-2
  s_trough3:
    number: 3-3
  s_trough4:
    number: 3-4
  s_trough_jam:
    number: 3-5
coils:
  c_plunger:
    number: 2-1
    default_pulse_ms: 20
  c_trough_eject:
    number: 3-1
    default_pulse_ms: 20
ball_devices:
  bd_trough:
    ball_switches: s_trough1, s_trough2, s_trough3, s_trough4, s_trough_jam
    eject_coil: c_trough_eject
    tags: trough, home, drain
    jam_switch: s_trough_jam
    eject_coil_jam_pulse: 15ms
    eject_targets: bd_plunger
  bd_plunger:
    ball_switches: s_plunger_lane
    eject_coil: c_plunger
    player_controlled_eject_event: s_launch_button_active
    eject_timeouts: 3s
playfields:
  playfield:
    default_source_device: bd_plunger
    tags: default

What if it doesn't work?

Have a look at our troubleshooting guide for ball_devices.

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