One USB-C cable, and the 2 A rule
The module makes 12 V out of USB-C, so one cable runs the whole kit. The quick-start guide asks for a 2 A adapter and is emphatic about not using a laptop port, and the reason is the coin motor rather than the steady draw.
Up, not down
Most breakout boards in a drawer step a voltage down. This one steps it up: the metal cube in the middle of the board is an inductor, and with the chip beside it that makes a boost converter, turning the USB-C 5 V into the 12 V the acceptor runs on.
That is why there is no barrel jack and no 12 V brick in the box. It also means the current the adapter has to supply is larger than the current the acceptor draws, because the same power at a lower voltage is more amps.
The arithmetic, and why the guide asks for more
The acceptor's own figure is 12 V at 350 mA, which is about 4.2 W. Pulled from a 5 V supply through a converter that is maybe 88 % efficient, that is a bit under 1 A. So the guide's 2 A is roughly double what the steady draw needs.
The margin is not padding. The number that actually collapses a rail is the coin motor's inrush — the moment the flap is driven and the mechanism turns, the draw spikes far above its average, and a supply that can only just manage the average sags instead. A sagging rail resets the acceptor's little computer, and a reset mid-coin means the coin is not counted.
What it looks like when the adapter is too small
The symptoms do not look like a power problem, which is why this page exists:
- Coins are rejected for no reason, or accepted intermittently.
- The two-digit display flickers or blanks.
- The acceptor restarts — you hear it re-initialise — every few coins.
- Everything works for the first coin after power-up and then stops.
None of that is a fault in your sketch and none of it is a training problem. Change the adapter first.
The cable counts too
A 2 A adapter on the end of a thin metre-and-a-half USB-C cable can behave like a 1 A adapter, because the voltage drops along the wire. If you have a short cable, use it. If the fault comes and goes when you wiggle the connector, that is the answer.
When it does not work
The rail is sagging. The steady draw is modest, but the coin motor pulls hard for a moment every time it runs, and a thin adapter cannot follow that. Try a 2 A phone charger and a different cable before you change anything else — a long thin USB-C cable can cause this on its own.
Do not. A typical laptop port offers about 0.5 A, which is below what the acceptor needs once the motor is turning. It may look fine while idle and then reject every coin, which is the confusing version of the same fault.
There is no input for it. The 12V pin on the acceptor-side header is an output — it is what the boost converter makes. Putting 12 V into it would back-feed the converter, so do not. If you have a 12 V supply and want to use it, it goes to the acceptor directly and the module is then only doing the signal half of its job.
Not once everything works. The VCC pin on the MCU side feeds your board from the same adapter. While you are still uploading code, leave VCC off and let your computer power the microcontroller — see wire it in this order.
Six connections, and one of them goes on last for a reason.
Wire it in this order →Edit this page — content/books/coin-acceptor/one-usb-c-cable.mdx
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Arcade Coin Acceptor Module Kit, USB-C Powered
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