As a reminder.....ALWAYS put a 0.1uf capacitor on the input of any 78xx regulator to ground as close to the device as possible. This is in addition to any electrolytic on the input. You'll be surprised how stable the regulator will be. Rick Francisco Ares wrote: > I had the oposite, in the bench it did not work and on the final > prototype it did! I used separate boards, one for the logic and other > for the relays that were activated by NPN transistors > > +12V > | > RL > | > C > logic >---->>---1KR-----B > signal conector E > | > GND > > Francisco > > Martin Peach wrote: > > >I have had this kind of problem and no amount of diodes in any configuration > >helped. Finally I shielded the PIC with metal and that did the trick. The > >EMF seems to have been radiated inside the box. > >/\/\/\/*=Martin > > > >----- Original Message ----- > >From: "Daryl Sayers" > >To: > >Sent: Monday, February 18, 2002 5:19 PM > >Subject: [EE] Power spikes reseting my pic > > > > > >>I have built a simple watering system using a PIC 1684. Works well on the > >>test bench but am having problems running live. > >> > >>I am using a 24V power pack (1A). The 24v is to power the solenoids to > >>open/close the water valve. I then cut this 24v down to 12v via a 7812 > >>to power the 12 relays that I use to activate the solenoids. I then > >>use a 7805 to get 5v to power the control circuitry. > >> > >>My problem is that I seem to be getting spikes (back EMF) into my > >>control circuitry that is reseting my PIC. I have put a diode across > >>each solenoid to limit the spike but this doesnt seem to be enough. > >>I put the diodes inside the box I built. Should I put something > >>right across the solenoid itself. I was thinking a filter cap. What > >>sort of cap and what value should I use. > >> > >> > >> > >> 12v 24v > >> | | > >> | | > >>RA1-4 |\ ULM2803 | > >> -----| \---------+ | > >> | / | | > >> |/ O -----+ > >> O \ > >> Relay O ------+-------------//-------------+ > >> | | O > >> | --- Long Cable O solenoid > >> | /\ Diode +---//-------------+ > >> | -- | > >> | | | > >> | | | > >> GND ----+---------+---------+ > >> > >> > >> 12v > >> | > >>24V +--------+ | +--------+ 5v to pic etc > >>--------| 7812 |--+---| 7805 |------- > >> +--------+ +--------+ | > >> | | | > >> | | |+ > >> | | --- 200uf > >> | | --- > >> | | | > >> | | | > >> | | | > >> GND ----+---------------+--------+ > >> > >>-- > >>Daryl Sayers > >>Corinthian Engineering Ph: (02) 9906 7866 > >>Suite 19, 401 Pacific Hwy Fax: (02) 9906 1556 > >>Artarmon, NSW, 2064 email: daryl@ci.com.au > >>Australia www: > >> > >http://www.cordoors.com.au > > > >>-- > >>http://www.piclist.com hint: The PICList is archived three different > >>ways. See http://www.piclist.com/#archives for details. > >> > >> > > > >-- > >http://www.piclist.com hint: The PICList is archived three different > >ways. See http://www.piclist.com/#archives for details. > > > > > > > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body