Basics of 74HC595
Hello friends, I hope you all are having fun in your lives. In today's tutorial, I am going to give you a detailed overview of this amazing shift register 74HC595. It must have happened to you that you are working on some project and you have to interface many LEDs etc with your microcontroller and at some point, you have no pin left for more LEDs. At that point, this shift register 74HC595 comes handy. 74HC595 is used to increase the output pins of your Microcontroller.
If you are new to this shift register then I would suggest you to have a look at 74HC595 Pinout and download its Proteus Simulation.So, let's have a look at its basic details:
Basics of 74HC595
- 74HC595 is a shift register which works on Serial IN Parallel OUT protocol.
- It receives data serially from the microcontroller and then sends out this data through parallel pins.
- We can increase our output pins by 8 using the single chip.
- We can also connect more than 1 shift register in parallel.
- So, let's say I have connected three shift registers with our microcontroller then our output pins are increased by 8 x 3 = 24.
- I hope I have cleared the idea, so now let's have a look at its pinout.
- As you can see from the figure it has below pinouts:
- Pin # 1 to Pin # 7 are Output Pins Q1 - Q7.
- Pin # 15 is also Output Pin Q0.
- Pin # 8 is Ground.
- Pin # 9 is Q7' (OutPut Serial Data).
- Pin # 10 is Master Reset.
- Pin # 11 is SHCP which is short for Shift Register Clock Input.
- Pin # 12 is STCP which is short for Storage Register Clock Input.
- Pin # 13 is OE which is Output Enable.
- Pin # 14 is DS which is Serial Data input.
- Pin # 16 is Vcc where we have to supply the power +5V.
- You can quite easily interface this shift register with different microcontrollers such as Arduino, PIC Microcontroller, Atmel etc.
Applications of 74HC595
It has a wide range of applications, especially in LED Boards. You must have seen the large LED boards where we have to control a lot of LEDs with a single microcontroller, 74HC595 is used in such projects a lot.
I hope you will like this article, let me know if you have any questions about this shift register and I will surely help you out. Thanks for reading, take care, bye bye !!! :)
CommentsAdd a comment
Hi, does the connection require exactly 8 leds? Can I achieve same results with say 7 leds? If yes, how do I wire them to the 595 ic seeing they are short 1 to make the 8?
@BayandaZikode, BradLevy is totally correct, do not use the HC595 for driving LEDs except as indicators or toys like an LED dice. RS supply some of the purpose designed chips for this purpose which are often used in car displays where you require dim for night driving and bright for daylight. The often have similar sounding part numbers presubably as the shift register is similar to the logic parts but the output circuitry is completely different designed for powering LEDs at high currents. The TPIC6B596N is an 8 bit example (but they also produce 12 bit). https://uk.rs-online.com/web/p/counter-ics/6608004/ Look up the TI datasheet for the full spec. I used an older version of these dedicated power shift registers to drive reed relay contacts to provide instrumentation control some time back and they did make life (design) simple and compact.
@BayandaZikode No, you don't have to have 8 LEDs. The unused outputs can be left open. Also be aware that the 74HC595 is not a good choice if you need to output more than about 5ma to each LED. (You should use a resistor in series with each LED to limit the current.) If you need higher output current to your LEDs, or to drive motors or relays, you can add transistor or IC driver circuits between the outputs of the 74HC595 and your loads. Or you can use different chips designed to drive higher loads directly. The 74HC595 is designed primarily for digital logic use, not as an output driver. But if you just need to drive some status LEDs, it can suffice.