Using a 74HC74 Integrated Circuit

74HC74-pins
74HC74 Pins

I received some advice to use a 74HC74 flip-flop for a project idea I’ve had. I’ve never used an integrated circuit so I thought a good first step was to put together a very simple demo I could hack around with it. This IC is big enough it actually provides two flip-flops, one on each side as you can see from the pin diagram on the right. Both sides work the same, but are completely independent other than sharing power and ground. I’m only using the first side for this example.

 

As I press the buttons connected to CLR and PRE, you can see the outputs (Q and not Q) alternate. I’ve set the data (D) and clock (CLK) pins to ground. The truth table for the 74HC74 comes in handy to understand what’s going on.

74HC74-truth-table.png

Here is a simplified wiring setup because it’s hard to see how everything is connected in the video.

74HC74-wiring.png

Also check out Combining 74HC74 & 555 Integrated Circuits.

3 Replies to “Using a 74HC74 Integrated Circuit”

  1. I set up your circuit and I had a problems. I moved the 200 Ohm resistor to pin 4 or left side of the switch and the ground wire to other side of the switch and it worked. If you look at your layout preset is always grounded.
    Thanks for the circuits I`m trying to teach my grandson.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s