Thanks. This is excellent advice. I do think I misled folks a little in my original post. Since I'm using a PC ATX power supply, I was powering the PIC with the 5V line and the motor with 12V. The 5v line had a reservior cap. I changed the circuit to power the PIC via the 12v line through a 7805 (properly cap'd). This really helped the reset problem -- even when I used the 'old' TIP which I thought was problematic. The downside is that I've introduced heat into the circuit that wasn't there before. Thanks again, Rob ----- Original Message ----- From: "Jinx" To: Sent: Thursday, June 03, 2004 10:47 PM Subject: Re: [EE]: 16F84 Reseting when controlling motor through TIP120 via PWM > > Lastly, I changed out the TIP120 and the problem seems to be fixed. > > No more resets > > > > Could I have blown something in the TIP during my first mistake that > > caused the TIP to appear to function properly but continued to cause > > the resets? > > Can say anything about that, but there is more you could do in the way > of reset prevention, especially when using a probably noisy component > like a motor (or relay/solenoid) > > Isolate the PIC's supply from the motor's supply with a diode and > reservoir cap. You could also add a small (47R-ish, depends on > what current you need for the PIC) series resistor. This will be the > initial noise filter. The motor side of the supply should also go through > a diode. In other words, split the 12V to go 2 ways through diodes, > one to the PIC and one to the motor. The reservoir cap will buffer the > PIC's Vcc against any nasties that get back through the diodes > > As well as the 10k to Vcc, Mclr should also have a cap (10n-ish) to 0V, > and a series resistor, 220R, and a reverse diode across the 10k (k to > Vcc), as per the manual > > A good solid ground is recommended too. You should scope it to > check for any noise. In very noisy environments you may need to > add Schottkys, at least, to prevent under-voltage on pins > > -- > 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 hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu