It's possible that the spike is being generated by the relay coil itself. Paul > From owner-piclist@mitvma.mit.edu Tue Feb 19 12:03:30 2002 > X-Comment: mitvma.mit.edu: Mail was sent by toole.uol.com.br > User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:0.9.4) Gecko/20011128 > Netscape6/6.2.1 > X-Accept-Language: en-us, es-es > MIME-Version: 1.0 > Content-Transfer-Encoding: 7bit > X-AntiVirus: scanned for viruses by AMaViS 0.2.1 (http://amavis.org/) > Message-ID: <3C725108.7020902@altec.com.br> > Date: Tue, 19 Feb 2002 10:20:08 -0300 > Reply-To: pic microcontroller discussion list > Sender: pic microcontroller discussion list > From: Francisco Ares > Subject: Re: [EE] Power spikes reseting my pic > To: PICLIST@mitvma.mit.edu > > 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