Driver Chip Decides Everything

The TM1637 needs just 2 pins and suits 4 digits. The MAX7219 drives 8 digits over SPI-style wiring and daisy-chains. The TM1638 adds key scanning for buttons. A bare display has no driver at all, so your MCU does the multiplexing.

Digit Height vs Viewing Distance

0.36-inch digits are fine at arm’s length on a bench instrument. 0.56-inch digits are readable across a desk or small room. For a wall clock or scoreboard you need 1.8 inches or more, and jumbo 4-inch digits need a separate 12 V supply.

Colon vs Decimal Points

Clock-style boards light a centre colon for HH:MM. Number-style boards light a decimal point after each digit for 12.34 readings. Check the product photos carefully, because many cheap TM1637 boards have only one or the other wired.

3.3 V vs 5 V Logic

TM1637 and TM1638 modules run happily from 3.3 V or 5 V, just a little dimmer at 3.3 V. The MAX7219 is specified from 4.0 V, so power it from 5 V. On an ESP32 or Pico, its 3.3 V data lines usually work, but a level shifter is the clean fix.

Chaining & Digit Count

Need 8, 12 or 16 digits? MAX7219 modules cascade through DOUT on three shared pins. TM1637 boards can share CLK but need a separate DIO for each, and the jumbo 74HC595 digits chain through a shift register. Plan pin budget before you buy.

The Lonely Binary 6-pack is what you buy when the display is going into something people will actually look at. You get six 0.56-inch TM1637 four-digit displays, one each in yellow, green, blue, white, orange and red, and unlike most cheap clock boards these have decimal points, so temperature and voltage readings work without tricks. Each display ships with a tinted anti-glare film and a 3D-printed enclosure, which takes a breadboard experiment to a finished panel in minutes. Wiring is standard TM1637: two GPIO pins, and multiple displays can share CLK with a separate DIO each. It is a newer listing with fewer reviews than the HiLetgo boards, but feedback so far is excellent.

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The TM1638 “LED & KEY” board is a complete front panel on one PCB: eight 7-segment digits, eight individual red LEDs and eight tactile buttons, all driven by a single TM1638 chip over three wires. The chip scans the keys for you, so reading button presses costs no extra GPIO, which makes this board a favourite for menu systems, kitchen timers, reaction games, test jigs and setting thresholds on a sensor project without a keypad. Libraries such as TM1638plus (Arduino) handle digits, LEDs and buttons together. Expect basic tactile switches and a modest 4.0-star average, so test every button when the board arrives.

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If you want bigger 0.56-inch digits in several colours but do not need enclosures, this five-pack is the budget route. It contains one TM1637 four-digit module each in red, green, white, yellow and blue, all using the same two-wire interface and eight-level brightness as the HiLetgo board, so the same code runs on every one. With nearly 150 ratings it is a well-proven listing. The modules are clock style with a centre colon, so check the photos if you need decimal points. It is a great pack for a classroom, a multi-zone temperature display, or simply finding out which colour reads best behind your enclosure window.

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For anything read from across a hall, the Lonely Binary 4-inch digit is in a different league. Each module is a single 100 mm-plus red digit on a custom driver board built around a 74HC595 shift register that switches the 12 V segments while accepting 3.3 V or 5 V logic. The boards snap together and daisy-chain on three GPIO lines, so a two-pack gives you a two-digit counter and two packs make a four-digit wall clock or scoreboard. Note that this is one digit per module, not four, and you need a separate 12 V supply alongside your 5 V or 3.3 V logic rail. Lonely Binary provides GitHub examples for ESP32, Pico and STM32.

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Sometimes you do not want a driver chip doing the work. The uxcell 0.56-inch common-cathode tube is a bare four-digit display: 12 pins (eight segment lines plus four digit commons) on a breadboard-friendly 2.54 mm pitch, with a forward voltage around 1.8 to 2.2 V at 10 to 20 mA per segment. You add resistors and drive it directly from GPIO, or through a 74HC595, which is exactly how you learn multiplexing, persistence of vision and timer interrupts. It is also the right part when you are designing your own PCB around a MAX7219 or HT16K33. Review count is small, so treat it as a component, not a module.

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Building a clock or countdown timer?

Get the HiLetgo TM1637. The centre colon is made for HH:MM, and it needs only two pins on any board.

Showing long numbers or a date string?

The MAX7219 8-digit module fits 12345678 or 2026.10.01 on one board, and cascades if you need more.

Displaying temperature or voltage?

You need decimal points. Choose the Lonely Binary 0.56″ (or the MAX7219), not a colon-only clock board.

Need buttons for menus or settings?

The TM1638 LED & KEY gives you 8 digits, 8 LEDs and 8 buttons on three wires.

Readable from across a room or hall?

Go jumbo with the Lonely Binary 4″ digits, chained together for a scoreboard or wall clock.

Teaching or learning multiplexing?

Use the bare uxcell common-cathode tube with resistors or a 74HC595, then graduate to a TM1637.

What is the difference between TM1637 and MAX7219 display modules?

The TM1637 is a low-cost driver for up to six digits that uses a two-wire serial protocol (CLK and DIO) and is almost always sold on four-digit boards. The MAX7219 drives up to eight digits, uses a three-wire SPI-style interface (DIN, CS, CLK), has 16 brightness steps and a cascade output for chaining many modules on the same pins. Pick the TM1637 for simple four-digit clocks and counters where pin count matters, and the MAX7219 when you need eight digits, decimal points on every digit, or several displays in a row. See our TM1637 Arduino tutorial to get started.

Is the TM1637 an I2C display?

No, although it looks similar. The TM1637 uses a two-wire clock and data protocol, but it has no device address and does not follow the I2C start and acknowledge rules exactly. That means it cannot share an I2C bus with sensors, and you cannot put two TM1637 displays on the same two pins. You can share the CLK line between several displays, but each one needs its own DIO pin. If you want a genuine I2C 7-segment display, look for an HT16K33-based backpack instead.

Can I use these 7-segment modules with an ESP32 or Raspberry Pi Pico at 3.3 V?

TM1637 and TM1638 modules work well at 3.3 V; the LEDs are just slightly dimmer than at 5 V. The MAX7219 is specified for a 4.0 V to 5.5 V supply, so power its VCC from the 5 V or VBUS pin. Its inputs often accept 3.3 V data lines in practice, but that is outside the datasheet guarantee, so add a 74AHCT125 or similar level shifter for a reliable build. Our TM1637 with Raspberry Pi Pico guide shows the wiring.

Common anode or common cathode: does it matter?

For driver modules like the TM1637, MAX7219 and TM1638 boards, no; the board is already wired to suit its chip and you never touch the segments directly. It only matters when you buy a bare display. Common cathode digits connect all the LED cathodes of a digit together, so you drive segments high and pull the digit low, which is what the MAX7219 expects. Common anode is the reverse. Mixing them up simply gives you an inverted or blank display, so match the bare tube to your driver or code.

How many 7-segment displays can I connect to one Arduino?

With MAX7219 modules the usual limit is eight chained displays per three-pin chain in the LedControl library, which is 64 digits, and you can run extra chains on other pins. With TM1637 boards you need one DIO pin per display plus a shared CLK, so an Uno can realistically run eight to ten. Jumbo 74HC595 digits chain indefinitely on three pins, limited only by refresh speed and your 12 V supply. Current is the real constraint: budget roughly 20 to 80 mA per four-digit module at full brightness and use an external 5 V supply for large builds.