Summary of 72 CHANNELS SERIAL TO PARALLEL DRIVER BOARD USING 74HC595 & ULN2803
This project is a 72-channel SPI-to-parallel driver board using 74HC595 shift registers and ULN2803 Darlington arrays to convert 5V logic serial data into up to 72 high-current sink outputs (12–48V load supply). Each output can sink up to 500 mA. Typical uses include multi-solenoid control, large 7-segment displays (up to 9 digits shown), bar graphs, LEDs, timers, scoreboards, and more. Outputs connect via a 10-pin box header; 2.3 inch 7-seg displays require 470 ohm series resistors when using 12V supply.
Parts used in the 72 CHANNELS SERIAL TO PARALLEL DRIVER BOARD:
- 74HC595 shift register ICs (multiple to reach 72 channels)
- ULN2803 Darlington transistor arrays (multiple)
- 10-pin box header connectors (one per output group)
- CN1 Data In connector
- CN2 Load supply connector (12V to 48V DC)
- 5V logic supply (power source)
- 12V to 48V load supply (power source)
- 2.3 inch 7-segment displays (example: 3 digits shown; up to 9 digits supported)
- 470 ohm series resistors for 2.3 inch 7-seg displays when using 12V
- Wiring/traces and PCB for interconnections
72 channels Serial (SPI) to parallel driver board has been designed for various applications. This project can be used as multi Solenoid driver, large size 7 segment display driver, bar graph driver, and LED driver. The project works with 5V logic levels. Output load supply 12V-48V DC and each output can drive 500mA load.
I have used 3 digits 2.3Inch 7 segment displays as an example, this board can handle up to 9 digits. The board can serve many applications like, Stop Watch, digital timer, counter, score board, token display and lot more.
Project built around 74HC595 and ULN2803 ICs, The 74HC595 devices contain an 8-bit serial-in, parallel-out shift register that feeds an 8-bit D-type storage register. The storage register has parallel 3-state outputs. Separate clocks are provided for both the shift and storage register. The shift register has a direct overriding clear (SRCLR) input, serial (SER) input, and serial outputs for cascading. When the output-enable (OE) input is high, the outputs are in the high-impedance state. Both the shift register clock (SRCLK) and storage register clock (RCLK) are positive-edge triggered. If both clocks are connected together, the shift register always is one clock pulse ahead of the storage register. All 8 parallel output are connected to inputs of ULN2803 which is an array of 8 Darlington transistors, each transistor can sink current up to 500mA.
The ULN2803A is comprised of eight high voltage, high current NPN Darlington transistor pairs. All units feature a common emitter and open collector outputs. To maximize their effectiveness, these units contain suppression diodes for inductive loads. The ULN2803A has a series base resistor to each Darlington pair, thus allowing operation directly with TTL or CMOS operating at supply voltages of 5 V or 3.3 V. The ULN2803A offers solutions to a great many interface needs, including solenoids, relays, lamps, small motors, and LEDs. Applications requiring sink currents beyond the capability of a single output may be accommodated by paralleling the outputs. Each output directly connected to 10 Pin Box header connector including 12V supply. The connector helps to interface display board or any other load.
Note: 2.3Inch 7 Segment display required 470 Ohms Resister in series for 12V load supply.
SPECIFICATIONS
- Logic Supply 5V DC
- Load Supply 12V-48V
- A ULN2003 IC helps sink higher current through load
- CN1 Data In connector
- CN2 Load supply 12V To 48V DC
- BH10 Box Header connector to connect the load
Read more: 72 CHANNELS SERIAL TO PARALLEL DRIVER BOARD USING 74HC595 & ULN2803
- What logic voltage does the board use?
The board works with 5V logic levels. - What range of load supply voltages are supported?
The output load supply can be 12V to 48V DC. - How much current can each output sink?
Each output can drive or sink up to 500 mA. - Which ICs are used to convert serial data to parallel outputs?
74HC595 shift register ICs are used for serial-in, parallel-out conversion. - Which device sinks the output currents to loads?
ULN2803 Darlington transistor arrays sink the outputs to the loads. - How many 7-segment digits can the board handle?
The example uses 3 digits of 2.3 inch displays, and the board can handle up to 9 digits. - Are suppression diodes included for inductive loads?
Yes, the ULN2803 units contain suppression diodes for inductive loads. - Do I need series resistors for 2.3 inch 7-segment displays at 12V?
Yes, 470 ohm resistors are required in series for 2.3 inch 7-segment displays when using a 12V load supply. - How are outputs presented for connection to displays or loads?
Each output is connected to a 10-pin box header connector including the 12V supply for interfacing displays or other loads.
