How do you use a Shortwave Radio to check an oscillator frequency? -Dave David VanHorn on 04/11/2000 05:16:45 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: (bcc: David E Arnold/SYBASE) Subject: Re: 16F874 PIC Refuses to Start Up? -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 >How difficult is it to get crystals going generally? What can be wrong, >apart from a duff crystal? It's not. Make sure you have a paralell resonant crystal, and you have the right loading caps. The xtal's spec will say something like 18pF load (or some other value) Take two caps at twice that value, minus about 5pF as a first shot. In this example, then I'd want 31pF, 27 would probably be ok, 33 better. Make sure these caps return directly to the chip's ground pin. If you have a series resonant xtal, it will probably still "work" but you'll have to guess at the loading values (try 22pF caps) and it won't ever get to the frequency that the crystal says it's cut for. (impossible) > >> If a scope is not handy then you could try a simple signal >> detector connected to a voltmeter. A DVM will usually read about 2.5V when connected to the osc out pin A shortwave radio with BFO is real useful for checking oscillation, and frequency. There are exact frequency signals at 2.5 5, 10, 15 and 20 MHz that you can use to check the receiver accuracy, and from that you can get a pretty good idea where your rock is singing. -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.2 for non-commercial use iQA/AwUBOPPAbIFlGDz1l6VWEQLA+ACggMYbQc4+w+L2eVz7bCkDZyEsBaMAnAph IblV43fNjjxSMH443ScySMAs =vkQG -----END PGP SIGNATURE-----