Let's Make Robots!

Relating clock crystal and 555 timer

And this may sound sttupid but can a 555 timer be used instead of a clock crystal/oscillator/resonator? If yes, then how? If no, then why? I'm asking this because I'm living in a place where a 555 is cheaper than the clock crystal...


UPDATE-

Well bajdi told me that the 555 is incapable of producing that frequency (first man to do so). What I undersatand now is-

  1. The 555 is slow and suitable only for small frequencies in the order of a few kilohertz.
  2. The required capacitors and resistors are not available to use it at such high frequencies.

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FYI one 16MHz crystal costs 0.07$ plus shipping at Tayda electronics. A ceramic resonator costs 0.23$. I hope you can get a credit card/paypal account sorted soon...

What is your processor? A lot of them have built in oscilators. The ATmega MCU's have an 8MHz oscillator in the chip. Picaxe also have internal resonators.

The internal oscillators are usually not as accuate as an external crystal oscillator but unless super precise timing is an issue in your application then it won't matter.

I have an ATMega 328PU (as mentioned above) and I know it can run at 8MHz and when I boot it, I'll run it at 8MHz. However, I wanted to know if it was possible to use a 555 instead of a crystal. What I understand now is that its possible to use it (theoretically) but since its (the 555 obviously) too slow and the requided cap doesn't come in such small value, it is practically impossible.

Can't you buy online?

Look what I found in my links: http://probots.co.in/index.php?main_page=index&cPath=15_28

basile

However, I'm incapable of buying online atm. I have 2 debit cards both of which don't work online. I'm trying to get a credit card and I may have one within a month (if everything goes fine).

Look for a "resonator" if price is an issue. I don't know if it will be cheaper than a crystal in Uttar Pradesh, but it's a viable option for timing and you don't need to use capacitors with it. Here's some background: https://www.sparkfun.com/products/9420

Well, the price tag of <$1 seems quite soothing to eyes but sparkfun takes a lot of shipping charges so its useless. Till I can find a shop selling it locally at the same price, its not worth it. Also, look at the prices of the crystals I posted (if the page does open). Its 20INR which is $0.36 approx. and I can pick it up from the store as its about 7km from my home so no need for delivery charges. There is only one problem that the shop deosn't have a 16MHz crystal.

I think you'll have trouble getting a 555 to operate in the MHz frequency range. 

I agree.

You can technically use it but I don't think a 555 can oscilate as quickly as most crystals(16Mhz for example)

What microrocessor are you using? most recent microprocessors have a built in oscilator that can be used with no extra hardware.