Maybe better if using opto-coupler instead... just too keep power and logic away. Harder to light a led than introducing a noise wich will be amplified later. Well that's what i did as now.
Originally Posted by
mikebar
I had a look to the link you posted. Sound interesting, but exactly in which way you perform the points:
- i'll ensure the PIC Vdd line is correctly filtered
those usual 0.1uF and 10-47uF tantalum as close as possible of the PIC and as many 0.1uF as you have IC... one on each.. still as close as possible.
Bigger cap (47-220uF) + 0.1 uF close to the driver ics...
- i'll screen the PIC and controller section properly to avoid incoming noise and spikes
Proper ground plane design, ground routing, Power lines routing and size against regular signals. Maybe use a grounded metal cabinet to fit it.
- i'll insert a bead on the PIC gnd line
When i deal with multiple Gnds (analog, power, digital) i often add bead core on most of them, usually 1 on analog, 1 on digital.
Do a search for bead core, ground loop, ground plane, ground boucing and i'm sure you may learn a lot of it. It's long to explain and i'm sure i'll mess and miss something. There's pro and cons on each methods... same for ground plane. Sometimes they're usefull, sometimes not. If they're done correctly they're usefull, case not... it will cause you more bugs than benefits.
EDIT: oh i forgot... never leave unused pins floating... tie them somewhere, VDD, VSS via resistor or not. Leaving them floating but setting them to output do nothing good. At least never pass my tests in cars applications.
Last edited by mister_e; - 17th August 2006 at 05:17.
Steve
It's not a bug, it's a random feature.
There's no problem, only learning opportunities.
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