74HC595 2-digit 7-segment display: specs
A 2-digit, 7-segment LED display module that uses 74HC595 shift registers to drive the segments from a serial input. The values below describe the SN74HC595 chip; the module board, its header and its segment resistors are not covered by an official document.
Specs
| Spec | Value | Source |
|---|---|---|
| SN74HC595 supply voltage (VCC) | 2 V to 6 V recommended (5 V nominal) | source 6.3 Recommended Operating Conditions |
| SN74HC595 absolute maximum VCC | 7 V | source 6.1 Absolute Maximum Ratings |
| SN74HC595 high-level input voltage (VIH) | 3.15 V min at VCC = 4.5 V | source 6.3 Recommended Operating Conditions |
| SN74HC595 output drive | +/-6 mA at 5 V (feature line); continuous output current +/-35 mA absolute maximum | source Features (p.1); 6.1 Absolute Maximum Ratings |
| SN74HC595 register | 8-bit serial-in, parallel-out shift register with 3-state output register | source Features (p.1); Description |
| SN74HC595 operating temperature | -40 to 85 C (SN74HC595) | source 6.3 Recommended Operating Conditions |
Power
| Value | Source | |
|---|---|---|
| Supply | Chip: 2-6 V VCC (module supply not documented) | source Features (p.1) |
| Current | Chip supply current 80 uA max (LED current is extra) | source Features (p.1) |
Pinout
We don't publish a pin table for this part: no official source we could verify gives one. Check the labels printed on your module, and see the notes below.
The chip pin names (SER, SRCLK, RCLK, OE, SRCLR, QA-QH, QH') are not listed as pin rows because the module's header labels, and which of them are brought out, are not documented. Check the printed labels on the board.
Build with it
Project ideas for the 74HC595 2-digit 7-segment display. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Two-digit counter: The Uno 5 V logic suits a 5 V module. Match the module's printed pin labels to your code.
- Temperature in whole degrees: Two digits cover whole degrees; the Nano drives the shift registers from three pins.
- Dial readout: A potentiometer on an analog input mapped to 0-99 is a simple first test of the display.
Common mistakes
- Powering a 5 V module from a 3.3 V logic board: at VCC = 4.5 V the chip's VIH is 3.15 V, so 3.3 V is marginal at 5 V; confirm the module or use a 5 V board (source: link, 6.3 Recommended Operating Conditions)
- Exceeding the supply rating: the absolute maximum VCC is 7 V (source: link, 6.1)
- Loading outputs too hard: the sheet gives +/-6 mA drive at 5 V and a 35 mA absolute maximum per output, and the module's resistor values are not documented (source: link, Features and 6.1)
Not covered by the official source
- Chip facts only: the module is not documented. The digit current, common-anode or cathode type and number of 595 chips are unconfirmed.
- The SN74HC595 VIH row at 3.3 V is not tabulated; only 2 V, 4.5 V and 6 V rows exist.
Sources
- link (TI SN54HC595/SN74HC595 datasheet SCLS041J, rev. Oct 2021; second-source maker)