Which Capacitor I needed

Other Hardware General Electronics
1

I am finishing a DIY item which contains:

  • 1 x ATtiny85
  • 1 x 74HC595
  • 7 x LED (Red color)
  • 7 x 300 Ω Ohm
  • 1 x CR2032 (Seems not working cause too low voltage, but actually I planned to use this)
  • 1 x Li-ion Rechargeable battery (280mA - 700mA, both work but the size too large, want a slim case)

The stuff is using ATtiny85 via 74HC595 to control 7 LEDs to blink. All the LEDs are ON often.

Question: Which Capacitor I needed, and where I put it into??

Detail information (Schematic, diagrams) can be share at here later.

  • Sorry for my poor English.

Screen Shot 2017-04-04 at 1.33.49 pm.png
Screen Shot 2017-04-04 at 1.33.49 pm.png2025×1030 281 KB

2

Share your schematic now. You will need a couple 0.1uF capacitors (ceramic are best for this use) attached directly to the Vcc pin of both chips, and grounded on the other leg of the cap. Do a site search for "decoupling capacitor".

3

CR2032 cells are good for 1mA or maybe 2mA, that might be something you don't realise.

You need to decouple each logic IC with 100nF on each supply pin to ground, and maybe
22 to 47uF electrolytic somewhere on the supply for good measure.

How are you clocking the ATtiny?

4

ChrisTenone:
Share your schematic now. You will need a couple 0.1uF capacitors (ceramic are best for this use) attached directly to the Vcc pin of both chips, and grounded on the other leg of the cap. Do a site search for "decoupling capacitor".

Sure, I will draw the schematic and upload to here asap, hopefully can be done in coming hours. :slight_smile:

5

MarkT:
CR2032 cells are good for 1mA or maybe 2mA, that might be something you don't realise.

You need to decouple each logic IC with 100nF on each supply pin to ground, and maybe
22 to 47uF electrolytic somewhere on the supply for good measure.

Ooops, seems that is impossible to using CR2032.

MarkT:
How are you clocking the ATtiny?

Following this tutorial to clocking ATtiny, High-Low Tech – Programming an ATtiny w/ Arduino 1.6 (or 1.0)

For this project, I am using internal 8MHz clock.

6

Hi all, attached the schematic to the post, thanks all.

7

Your battery symbol is drawn backward. The longer bar is positive:

         |
       + |
      -------
       -----
      -------
       -----
       - |
         |
8

ChrisTenone:
Your battery symbol is drawn backward. The longer bar is positive:

I am beginner, just thanks for your remind.

9

And you have drawn 2 cells in series - wasn't this a single CR2032?

10

I have three CR2032, but in this project I prefer use one only. After you mention there is only 2mA current output for each CR2032, I had Google, however, you are right. According to Wikipedia, the max pulse is ~15mA. Which is unable to make all LED on.

Therefore, I may use Li-ion rechargeable battery for this project, which is providing at least 3.7v, and I had a test, all LEDs both can blink.

But still want to know that, is it need a capacitor for this project?

11

Hang on, are you wanting a storage capacitor for powering the LEDs for pulses? You didn't say so.

Firstly you need 0.1uF decoupling caps on the logic chips as explained above.

Secondly for bolstering the supply for pulse operation you need to explain how much current for
how long you need - and how much voltage droop you can tolerate during the pulse.

12

Actually, I am finishing this stuff:
https://instagram.com/p/BSSok3Rjwpu/

13

Nice Job!

14

allen727hk:
...
But still want to know that, is it need a capacitor for this project?

I told you the answer in reply #1. You were probably dazzled by my ASCII art! :wink: