Beginner question with the 74HC595 shift register.

LED Flashlights – General Info
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So I got 2 74HC595 shift registers from spark fun to use with my book ‘Arduino Workshop’. If you are familiar with it, I am attempting to work on project 16 where you use a shift register (specifically the 74HC595) to light up a series of 8 LED’s to count from 0-255 in binary. Obviously that entails a lit LED being 1 and a non lit LED being 0. I finally got the thing hooked up correctly but the LED’s seem to dim as more of them are turned on at once, now this could be an incorrect assumption and something else is causing it but to be honest, I’m really unsure. I have included a link to a short video showing my issue.

If anyone understands what is happening and can either help me fix it or show me where I can find a solution, that would be tons of help!

And for the record, yes I have checked Google but can’t seem to find anything sadly.

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@nanawhite107, I can't find your link to your short video.

It would also help to have a circuit diagram of what you have wired up.

Best Regards,

George

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Normal. It’s a logic chip, not a driver chip. The more you try to sink (or source), the more juice has to go through the power pins, and there’s only so much they can handle. Voltage will start to sag, which is a good thing, because trying to pull too much current through it will let all the Magic Smoke out of it.

I’m assuming you’re directly hooking up LEDs to the chip, not through resistors or anything? Only makes it worse.

Use something like a 74HC244 to drive the LEDs… gently.