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Topic: Would this mobile xtal module work for breadboard? (Read 1 time) previous topic - next topic

wilykat

Oct 21, 2017, 09:52 am Last Edit: Oct 21, 2017, 10:10 am by wilykat
Many people may want to use ATMega or ATTiny chips on breadboard but the common standard XTAL can has 0.2" pin spacing and doesn't work well, forcing user to place the oscillator and capacitors somewhere else and route wires to the 2 XTAL pins.  However depending on the length or wires and quality of the breadboard, extra capacitance would be introduced and the circuit may fail to work properly. I didn't see the idea of a tiny XTAL on pins  that uses 0.1" spacing and can work with just about any standard 0.1" DIP chips that uses 2 XTAL pins next to each other.




2 pins are direct to XTAL pins via breadboard, the 3rd one would employee a short jumper wire to GND. Not all ATMega has convenient ground pin next to XTAL pin like ATTiny 24/44/84  Both top and bottom of PCB has ground pour to cover unused area and reduce risk of interference.

This would be useful for quickly bootloading new blank chips or to reprogram older chips to not use external clock anymore.

The reason for double clock pad is I have some cans that uses 0.1" spacing but the leads are very thin and won't survive more than a few uses in breadboard. Also more common 0.2" spaced XTAL will fit as well, just pick whichever you have on hand.

OSHpark quoted $1.50 for 3. I can upload it as shared if there's no issue with the design.

wilykat

Bump- anyone? Just say "It sucks it won't work" or something.

stowite

I don't do much with a breadboard these days (I use perf board for prototyping) but when I did I just bent the crystal wires until they spaced at 0.1" .

aarg

Have you actually had problems with the "extra capacitance" you mention? A centimeter or two of lead wire isn't going to affect things much. I've built lots of crystal circuits like that on breadboard without any problems. Don't forget to ground the case.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

wilykat

Someone did: https://forum.arduino.cc/index.php?topic=506562 and at post #10 and 11 they finally solved it by removing 2 capacitors, the wires alone was long enough to add capacitance.

MarkT

The flying lead for ground isn't a very low inductance path, but its probably going to work.  Note that
you can get ceramic resonators with in-built load capacitances, and they have a 3 pin pinout, ground
in the middle, so I would have suggested that for such a module.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

wilykat

Isn't resonators typically a bit less accurate?

MarkT

A _lot_ less accurate, and its a pain because the Uno uses a resonator for some unfathomable reason.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

DrAzzy

On breadboard, you just bend the leads. Everyone does that.

Have you actually had problems with the "extra capacitance" you mention? A centimeter or two of lead wire isn't going to affect things much. I've built lots of crystal circuits like that on breadboard without any problems. Don't forget to ground the case.
A few people doing it on breadboard have reported that they have to remove the loading caps to make the crystal work. It seems to depend on the specific breadboard (and maybe crystal).

A _lot_ less accurate, and its a pain because the Uno uses a resonator for some unfathomable reason.

Yeah. It's a real shame, esp since there's tons of space for a crystal, and the official board is sold at such an obscene markup
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

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