Choosing the right power supplies for your pinball machine

Wiring, high voltage, and electricity can be dangerous. Read this first!

The voltages and electricity discussed here can be dangerous and could cause property loss or death. It is your responsibility to ensure you are aware of these risks and comfortable with these processes. Furthermore your local jurisdiction may have regulations or rules which differ from what we discuss here, including wiring colors, standards, techniques, etc. Although based on broadly adopted methods, FAST Pinball does not employ Professional Engineers and this information is not professional recommendations. There may be errors, omissions, or typos here. Any pinball machine available to the general public should be reviewed by a licensed Professional Engineer in your region. Use this content at your own risk.

Your FAST Neuron-powered pinball machine will require two power supplies: 48-volts and 12-volts. These convert the high voltage AC power into lower voltage DC power you machine will use. There are many different types of power supplies (PSUs) in the market, so it's important that you know what you're looking for in order to get ones that will be safe and functional in your machine.

If you want to know how to hook up your power supplies when you're wiring your machine, check out the power supply wiring guide which is part of our larger series of step-by-step guides on pinball machine wiring.

Power supply recommendations for most machines

If you just want a TLDR recommendation for power supplies, here are some we like:

• 48V, Mean Well RSP-500-48
• 12V, Mean Well LRS-150-12 (12.5A), or
• 12V, Mean Well LRS-100-12 (8.5A)

You should be able to find these from many sources. Read on for details about why we like these specific ones or for important things to know if you're selecting your own.

Choosing a 48-volt power supply for your pinball machine

There are lots of things to consider when picking a power supply for your pinball machine. Let's step through them all here.

Power supply type

For new pinball machines today, you want to pick a switching power supply (sometimes called a switch mode power supply, or SMPS). The older linear power supplies you find in pinball machines from the 1990s, such as the heavy toroidal supplies or the ones with big transformers, are relics from the past analog world. They are bulky, heavy, hot, and inefficient, often passing only 50-60% of the power they consume on the AC side out of the DC side. (The rest becomes heat)

Switching supplies use modern solid state components. They are small, lightweight, efficient, and run cool.

The easiest way to tell if you have a switching power supply (the kind you want) is that its input voltage will be a range, such as 100-120VAC. Linear power supplies (the kind you do NOT want) have a fixed input voltage.

AC input voltage

Obviously you'll need to buy a power supply which matches the voltage of the country where you'll use it, such as 110-120VAC for North America and 220-240VAC for Europe. Some power supplies only work for one of those ranges. Others have a switch which you set to select the input voltage. And still others are automatic and can work across broad ranges like 100-250VAC. (These are known as "full range" power supplies.) You might think getting a full range supply means you can move your pinball machine between countries without changing any settings, which is almost true, though you'll still have to change the line fuse since that's a different value based on the input voltage. Full range supplies tend to be more expensive too and usually not worth it. (And again, how hard is it to flip a switch if you are moving a machine between countries?)

DC output voltage

A modern pinball machine based on the FAST Pinball platform is designed to use 48 volts DC for the coils and other high voltage devices. While older machines from the 1990s ran their coils on 70 volts, everything today is designed for 48 volts.

The reason for this is because most jurisdictions and regulating bodies consider anything under 50-60VDC to be "low power", and thus there are different wiring safety standards which are easier to implement. Plus lots of electronics and cars are moving to 48VDC nowadays, so 48VDC power supplies are plentiful and not expensive.

Current (amps)

Power supplies are rated by the max current (in amps) they can support at the DC output voltage side. So a 48V/5A power supply can supply up to 5 amps at 48 volts.

It's important to match your power supply to the needs of the machine, while also not picking a supply that can do too many amps since that can potentially be dangerous.

For example, the 0.156" headers used in the FAST Modern Platform ecosystem, as well as all the boards, are designed for a maximum sustained current of 7 amps. It's ok to choose a power supply that's slightly over 7 amps since proper wiring design and fuse selection will ensure its safe, but you don't want to go too far over that.

For example, the 48V power supply we recommend is rated for 10.6A at 48V. That's ok, because our wiring guidance will split this load over multiple wires and fuses, which we can do safely. But if you asked us if a 20A power supply was okay, we'd say no because there are many other things to take into consideration which are beyond the scope of this documentation.

Protection type / failure mode

Next, take a look at the "failure mode" or "protection type" of the PSU. This describes what happens when whatever's connected to the power supply attempts to draw more current than the supply is rated for. Some power supplies temporarily reset. Others have internal circuit breakers. Some cycle on and off really fast. There are lots of options here but only one type you want to use in pinball.

The reason this is important is because when a high-current coil (like a flipper power winding) is activated, it is almost like a dead short and will use a lot of power, something like 10-15A or more. (And you could have 3 or 4 flippers all activating at once!) So even though your machine and the power supplies are designed for a maximum of 7 amps, that is the max sustained over a long time. But it's necessary for your machine to be able to use much more than 7 amps for very short bursts of time (perhaps only a few tens of milliseconds while the flipper power stroke is on).

If you have a power supply that instantly shuts off when you hit a flipper because it went above its rated current, well, that is not a good power supply for a pinball machine! :)

So you need to find a 48-volt PSU that goes into "constant current" mode when its limits are exceeded. Constant current mode means that in order to maintain the current (amps), the power supply will drop its voltage. This is ok because the FAST Power Filter Board has those three huge capacitors which have reserve power stored in them which will make up for the lost voltage from the PSU while this is happening. (Those capacitors are constantly discharging and recharging as the machine is played.)

Inrush current

The next thing you need to look at (if you will be using the soft power control option) is the inrush current. Inrush current is essentially a huge current spike that occurs when the power supply is first turned on. You need to look at this value to ensure you buy a solid state relay which can handle the current. (Actually it will need to handle the combined inrush currents of the 48-volt and 12-volt supplies.)

You will notice that the power supply's data sheet will have different values for different input voltages. The 48-volt supply we recommend has an inrush of 20A for 115VAC input power and 40A for 230VAC.

(By the way, most computer power supplies have crazy high inrush current ratings which is why we do not like computer PSUs in pinball, not even for bench testing, as it can shorten the life of various components.)

Fan or no fan?

Most 48V switching power supplies have fans, which can seem annoying. (It seems like every time the machine gets busy, you hear that loud fan!) While it's temping to buy a supply without a fan, if you do, pay attention to the requirements for ambient temperature, airflow needs, and cubic inches of free air, and positioning next to other things (such as the 12-volt supply). Fanless can be a pain to make work with all these various requirements.

If you get a PSU with a fan, pay attention to any guidance around incoming air flows and temperatures. For example, you wouldn't want to install a power supply right up against the side of the backbox if that blocks the vent holes where the supply draws fresh air from. And you also need to ensure the internal temperature of your backbox doesn't get too hot and exceed the rated temperature requirements for the PSU.

That said, you can also check the data sheet to see what happens when the PSU goes over temperature. Most of them will simply shut down, which is great, because you can install it as you wish and then if it shuts down, do some more thinking about how to keep it cool.

Example 48V PSU we like: Mean Well RSP-500-48

Let's take all this theory and put it to practical use. This is a snippet of the data sheet for the Mean Well RSP-500-48 which is the 48V PSU we sell in the FAST Pinball shop. We've highlighted the most important parts:

Notice that this data sheet is used for the entire series of RSP-500-xx power supplies, and we're just interested in the 48V version. The upper right corner shows us that it's 48V DC output at 10.5A.

Next we see that the input voltage range is wide, which means it's a switching power supply, and also it covers both 120VAC of North America and 240VAC for Europe.

Next, we note the inrush current values which we'll need to calculate the size of the solid state relay we use to turn it on (if you're going that route).

We also see that the overload protection type is "constant current limiting", which is critical for use in a modern pinball machine.

Finally, the over temperature behavior is to shut down, which will safely inform us that we need better ventilation or cooling if it gets too hot.

This is a great 48V power supply for a pinball machine! (Again, there are others which are fine too. This is just an illustrative example which shows why we chose this one.)

• DC Voltage: 48V
• Rated Current: 10.5A
• Input Voltage: 85-264VAC
• Inrush Current: Listed
• Overload Protection Type: Constant Current
• Over Temperature Protection Type: Shut down
• Fan: Yes

Choosing a 12-volt power supply

The 12-volt power supply in a FAST Neuron-powered pinball machine is used for everything else other than the coils and magnets. This includes:

• The FAST boards
• Display(s) (LCDs, segments, and/or DMDs)
• Audio amps
• LEDs (they run on 5V but pull that from the 12V PSU)
• Shaker motor
• Optos
• Host PC (it's possible to run it from a different voltage but finding a 12V one is preferred)
• Lower current coils, servos, and stepper motors

The way the 12V supply is used in a pinball machine is quite different than the 48V supply. The 48V supply is "spikey" in that when no coils are actively firing, it's not being used at all. Then when the coils fire, it's stressed to it's max. (Actually it's stressed beyond its max which is why the power filter board has those three huge capacitors.)

The 12V supply, on the other hand, is used much more evenly. Really the only thing that really moves the 12V current up and down is the LEDs. If all the LEDs turn on at once, that will draw more current then when they're all off. But even so, that's within a much narrower band.

Quick math: Let's say an RGB LED on at full brightness is 60ma. So if there are 100 LEDs in your machine, that could be 6000ma total (or 6A). However LEDs run at 5V, so 6A and 5V is 2.5A at 12V. If your 12V PSU is rated for 10A, it might run at 5A while it's powering everything else in your machine with the LEDs off, and then go up to 7.5A with all the LEDs on. Both of these are well within the range of what the PSU can handle, (which is why you don't need those huge capacitors for your 12V circuit.)

(Also, 60ma would be the max power consumption for an LED on 100% full white, which is REALLY bright, and also how often will your machine turn on all LEDs full white? So in practice, all the various LEDs changing color throughout your game will probably only vary the 12V current by an amp or two which isn't a big deal.)

AC input & power supply type

The AC line input considerations for your 12-volt supply are the same as the 48-volt supply. Obviously make sure it can use whatever voltage level you have. And of course you want 12 volts on the DC output side.

You also want to ensure you select a switching power supply, not a linear supply, just like with the 48V one.

12-volt current (amps)

Again, every power channel in FAST Pinball hardware is designed for a max of 7 amps.

It's possible to go over 7A as long as multiple power wires are used and everything is fused appropriately. We'll cover this in detail through the wiring design guides.

For example, you might use 3A for your host computer, 3A for your audio amps, and 6A for the rest of your machine. So a 12V PSU providing somewhere in the 8-13A range is probably a good target. (Again, this depends on many factors, see the wiring guides for details.)

Inrush current

Many of the 12 volt power supplies only list their inrush current at 230VAC, so if you're running at 115-120VAC like in North America, you would adjust that number accordingly. (Essentially it would be cut in half.)

Here are two examples of 12V power supplies which could work well in a pinball machine.

(more to come...)

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