[Aaron] just finished building an online 595 shift register simulator. These inexpensive chips let you extend the number of devices that can be controlled by a single microcontroller. You see them in quite a few LED multiplexing projects, included the Ping Pong Clock that we recently built. But they can be a bit tricky to fully grasp if you’re not familiar with the hardware.
This simulator gives you a point-and-click interface for the five possible control lines on a 595 shift register. There are three pins that must be manipulated to use the device; the serial in, clock, and latch pins. The other two are for clearing the register, and enabling output and can be considered optional. You can choose to control these with a microcontroller in your own projects for more flexibility, but often they are tied to either VCC or GND (depending on the chip) when these features are unnecessary. Give this simulator a try and then take what you learned over to a solderless breadboard and see if you can write some firmware to produce the same results. If you’re still having trouble you can take a look at this 595 tutorial for further information.
Very nice. Just learned something!
Awesome, the 74HC595’s are very nice and inexpensive chips for microcontroller projects. They’re easy to use and can control many devices from only 3-4 pins. With a standard ATMega168 at 20MHz I was able to get software-PWM out of 3 595’s chained together to drive 8 RGB LED’s. It took pretty much every bit of power the chip had but it was decent PWM. I also use 595’s when connecting parallel LCD’s to save a few pins.
Love it!
omg i now i finally get how shift registers work!
this is great!
I love this. There should be more interactive tutorials like this! Actually, I just remembered that there’s a site that has all sorts of logic tutorials like this: play-hookey.com.
Is there a standard way to use several 595 chips to drive a multi-digit seven segment display (e.g., common cathode)? I would guess the /OE pin would come into play there. Or maybe when using 595s it’s just better to have separate digits…
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More info!