pic16f882 timer1 clock crystal - Page 2 - Electronic Circuits Projects Diagrams Free

Pommie · 29th October 2009, 01:47 AM

Mine is on a breadboard with 15pF caps and is still keeping good time after a day.

Mike.

Mike, K8LH · 29th October 2009, 02:01 AM

I suspect not all solderless breadboards are created equal (lol). The very old solderless breadboard I have doesn't like crystals at all.

Regards, Mike

Sceadwian · 29th October 2009, 03:11 AM

Pommie, put the same circuit on a perfboard, I garuntee it won't keep the same time.

birdman0_o · 29th October 2009, 04:27 AM

So I should avoid a breadboard? Using a 10pf on one leg and 33 pf on another I got accurate time for about an hour...

Sceadwian · 30th October 2009, 01:39 AM

You could do that, but you'll have to use a variable cap to tune this on the final board, or retune it completly once it's in it's final enclosure. Scope leads don't help either.

birdman0_o · 30th October 2009, 03:18 AM

Trimmer cap, genius idea!

Now I just need to think of a good way to tune it accurately without wasting half my life

Sceadwian · 30th October 2009, 03:24 AM

You can use trimmer caps in serires with static ones too if you have am in value in mind.

ericgibbs · 30th October 2009, 09:34 AM

Quote:

Originally Posted by birdman0_o

So I should avoid a breadboard? Using a 10pf on one leg and 33 pf on another I got accurate time for about an hour...

hi Boo,
Use a epoxy perf pcb with a simple trim cap say 3 to 30pF and the timing accuracy will be within the spec of the crystal and the associated caps.

If you use SRBP perf pcb, varnish the pcb copper area around the crystal and trimmer cap.

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29th October 2009, 01:47 AM	#16
Pommie	Mine is on a breadboard with 15pF caps and is still keeping good time after a day. Mike.

29th October 2009, 02:01 AM	#17
Mike, K8LH	I suspect not all solderless breadboards are created equal (lol). The very old solderless breadboard I have doesn't like crystals at all. Regards, Mike

29th October 2009, 03:11 AM	#18
Sceadwian	Pommie, put the same circuit on a perfboard, I garuntee it won't keep the same time. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

29th October 2009, 04:27 AM	#19
birdman0_o	So I should avoid a breadboard? Using a 10pf on one leg and 33 pf on another I got accurate time for about an hour... __________________ Mike My website: www.ElectroBird.net

30th October 2009, 01:39 AM	#20
Sceadwian	You could do that, but you'll have to use a variable cap to tune this on the final board, or retune it completly once it's in it's final enclosure. Scope leads don't help either. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

30th October 2009, 03:18 AM	#21
birdman0_o	Trimmer cap, genius idea! Now I just need to think of a good way to tune it accurately without wasting half my life __________________ Mike My website: www.ElectroBird.net

30th October 2009, 03:24 AM	#22
Sceadwian	You can use trimmer caps in serires with static ones too if you have am in value in mind. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."