Stand-in capacitor to work with 16MHz crystal?

Forum 2005-2010 (read only) Hardware Development
1

I am building my first non-breadboard Arduino project. I have it working on the breadboard, soldered all the pieces together on my proto board, and it didn't work. Then I realized there was a typo in the instructions I was following for the Arduino schematic. I used two .22pf capacitors with my crystal, and apparently should have used 22pf.

Unfortunately, the local Radio Shack doesn't have 22pF capacitors, and my little RS assortment doesn't have one, either. So, I'm hoping that there is something I can use as a substitute until my next Mouser order. I'm just too new to this stuff to be able to figure out the correct capacitor on my own. The crystal specs say it has an 18pF load capacitance - so does that mean I can just use two 18pF caps, one between each leg and ground? Of course, I don't actually have 18pF caps either :slight_smile:

Here's the crystal I'm using: http://www.mouser.com/Search/ProductDetail.aspx?R=AB-16.000MHZ-B2virtualkey52750000virtualkey815-AB-16-B2

Here's the instructions I was using so that you can see the schematic: http://arduinofun.com/files/byoa.pdf

2

I don't know much about crystals, but I am interested in answers you get. For my own, these links might help:

http://www.oscilent.com/spec_pages/PNDescrpt/Load_Cap.htm
http://www.foxonline.com/techfaqs_cry.htm

Good luck!

:slight_smile:

3

I used two .22pf capacitors with my crystal

Are you sure, I don't think .22pf is even avalible in through hole mounting. Maybe you got 2.2pf?

Lefty

4

Yes I don't think you can get 0.22pF in a leaded component as the capacitance in the leads is going to be more than this.

Basically you should be able to use any value between 18pF and 33pF without too much difficulty.

5

Sorry, you're right. I had two 0.22µF (these: RadioShack.com Official Site - America's Technology Store)

6

I had two 0.22µF

Ok much too large. 0.22uF is not .22pF as you first stated having. .22uF is one million times larger then the desired 22pf.

Lefty

7

.22uF is one million times larger then the desired 22pf.

Only 10000 times larger. 0.22E-6/22E-12
:slight_smile:

8

Only 10000 times larger. 0.22E-6/22E-12

Yea, what you said. Still way to big. :wink:

Lefty

9

While you are waiting for 22pf caps, try it with no caps at all. It's not recommended, and it might not work, but it can't hurt anything. Just leave space for them on your protoboard.

I've got a couple of boards I've been using for about a year with a crystal but no caps.

-transfinite