74HC595 & 74HC165 Shift Registers with Arduino

@codecage

I think this might work. If not, then I have created a small datasheet for this.

Here it is. Please have a look. 🙂 

@codecage

Posted by: @codecage

@frogandtoad

I think his diagram (other than labeling the commons as Vcc) better represents his device.  His decimal point is on pin 9 not 6, as 6 is not connected to anything on his device.  Pin 6 would have been for an additional decimal point in the lower left corner of the device.  His diagram definitely has the right number of pins. But it could have included the pin numbers.

Hi Steve,

I understand, but I think you may have misinterpreted my post.

I didn't provide the image for the pins and numbering to be copied directly, it was just to be used as a reference, for how such devices are drawn and depicted for clarity.

Cheers.

Hello to all, I’ve set up the 595 as per the tutorial with a row of 8 LEDs to display the output in binary. My set up gets to 63 on the display then and returns to 1 again. I’ve tried changing the 595 for another and it made no difference..
the for loop is set at <256 and I’m baffled..can anyone help please ?

Sorry guys, sorted the problem now, but can’t see a delete button to remove my post 

Also there’s an edit button and a delete button on this box but not on my original post ? Oh well, all will become clear one day. .

@graham410

There is a timeout timer so to speak on how much time can pass while you can still edit a previous post.  Once that time has passed, and I'm not sure what that time is, then you can no longer edit the post, so I would guess the delete functionality probably goes away as well. A recent post should have both edit and delete capabilities.

@codecage thank you for the information, much appreciated...

All’s worked out fine now...

@codecage

Hi. Have you seen the diagram of the 7 segmented LED display? It's the model which I have. It's different from the conventional displays, most of the people have. 

I will be using this to control a bank of relays. However, when the Arduino powers up, all outputs of the 74HC595 go high for about 1 second. This means everything connected to my relay bank will activate for a second whenever the Arduino is powered on. How can I prevent this from happening?

New to the forum. Is this the correct place for this question?

A question about the current on 74HC595:

I tried the first sketch, using  220 ohm resistors, one for each LED, but on Thinkercad it gives me error since the IC is driving too much current when every LED is ON.

On the datasheet I read : Io MAX 35mA.

So, how can it drives all 8 LEDs?
What am I missing ?

Thanks!

Posted by: @boggiano

A question about the current on 74HC595:

I tried the first sketch, using  220 ohm resistors, one for each LED, but on Thinkercad it gives me error since the IC is driving too much current when every LED is ON.

On the datasheet I read : Io MAX 35mA.

So, how can it drives all 8 LEDs?
What am I missing ?

If you need to drive all of the LEDs at once, you'll need to use a transistor. Use the output from the 74HC595 to trigger the transistor to power the LED.

@boggiano IIRC you only have 40ma max per pin, so you will need some way to separately power the leds. I know a MOSET will work, but there may be other solutions. Of course this assumes all the LED's are supposed to turn on at once.

@boggiano 

If you don't mind squeezing the 35 mA total throughput, you could change all of the dropper resistors on your LEDs to cut the power down to 3 or 4 mA per LED. They'd still light (although dimmer) but that would keep the total power sucked from the 74HC595 within its limit.