These printers use a thermal head to heat the special receipt paper and draw images and text. That makes them very small — there's no moving ink head — but it means they require a lot of power: 5 to 9 Volts DC, at least 2 Amps of current. That means you will need a fairly beefy supply and you cannot run it off of USB power. An external adapter is required!
As a baseline, we suggest the 5V 2A power supply in our shop. It provides sufficient power to keep the printer happy, and usually enough overhead to power a modest microcontroller project along with it.
A quick way to connect this to the printer’s red/black power wires is with a 2.1mm jack adapter:
The 5V 2A supply mentioned above is a baseline. If using this, you might want to power the microcontroller separately through its USB port, to prevent a brownout condition when the printer is drawing a lot of current. Higher current supplies — 4 Amp and 10 Amp* — are also available in the shop, bulkier but with ample overhead for both the printer and supporting hardware you might be adding.
The higher current can make for darker printing and quicker, more assertive paper feed. Slightly higher voltage can too — to a point. One should never exceed 9 Volts to the printer; 12V or more will permanently damage it! 2A (or more) current is still recommended at these higher voltages. If upcycling a power supply from something else, carefully check the polarity (most, but not all, are “tip positive”) and that the output is DC, not AC.
A benefit to 5V power is that many dev boards can run from this directly and will regulate to 3.3V if needed; only a single power source is needed. That’s not necessarily true with higher voltages…though some, like the Arduino Uno, can accept 9V through the board’s DC power jack.
* The printer will never draw anywhere near this much current, but larger supplies are less susceptible to voltage droop when there’s a sudden demand. Sometimes just a matter of what’s presently in stock without waiting, or what other projects you might want to use this with in the future (e.g. large NeoPixel projects could benefit from the extra capacity of a 4A or 10A 5V supply).
The Mini thermal printer has two 3-pin sockets—one for power, one for serial communication. Power goes to the jack labeled “DC IN.” Only the outer two pins of this connector are used.
The Tiny printer has three sockets: a 2-pin connector for power, 5-pin for TTL serial communication, and a USB port.
DO NOT attempt powering from the red and black wires of the serial cable. This cable is not following common electronics color conventions and connecting power here may damage the printer! Use ONLY the 2-pin connector for power.
The Nano printer and “printer guts” have a single 5-pin connector for power and serial data. The outermost red and black wires are for +V and ground, following typical conventions.
During initial testing and for quick temporary projects, it’s usually okay to jam breadboard prototyping wires into the end connector on the DC power cable (or power+serial cable on Nano and guts), and the other end to a DC barrel jack adapter.
However, breadboard wires are small gauge and not suited to continuous heavy power draw. Once you’re “moved in” — confident the printer works and will suffice for a project — one option is to cut the DC cable, strip the wire ends and screw these directly to the DC barrel jack, without the breadboard wires as a go-between.
Keep the serial wires intact though. Breadboard wires work splendidly there.
The most robust option, if you want to get all fancy, is to splice a DC jack pigtail to the power cable.
This is not a part we carry. One option is to cut a DC barrel jack extension cable in half and use the socket end. Or, the pigtails are commonly used in security camera installations, so you might find something by searching around.