Post by thread:[PIC]: PIC reseting due to relays

Hello, I've got a 16f870 that I'm using to turn a relay (Tyco V23105 150 mW Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. This relay is controlling a very small DC motor (~0.5amps). About 10% of the time when this relay turns on/off, it resets the PIC. I've verified this is what's happening. Seems to work fine when the motor isn't connected to the relay. Only resets when the motor is connected. I'm using PORTA.0 through a resistor to turn on a 2N4401 transistor that then powers the relay coil. I have a 1N4004 diode across the relay coil. I have two 0.1uf caps on the +5v to the PIC. The +5v for the PIC is from a powered protoboard. The +12v for the transistor and relay are from a +12v battery. The grounds of these two power supplies are tied together. Can anyone help me figure out what's going on and fix this? Thanks, Gary -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Gary Neal wrote: >Hello, > > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 150 mW >Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. This >relay is controlling a very small DC motor (~0.5amps). About 10% of the >time when this relay turns on/off, it resets the PIC. I've verified this >is what's happening. Seems to work fine when the motor isn't connected to >the relay. Only resets when the motor is connected. ....... Sounds like you need a suppressor across the relay "contacts", or better yet at the motor itself. Since a DC motor, try a reverse diode there or a snubber - 10-100 ohm resistor in series with a 0.1 uF cap across the motor winding. The cap should be better quality than simple low-V ceramic. 200V or so polypropylene. - dan michaels http://www.oricomtech.com ======================== -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

At 02:36 PM 8/28/01 -0400, Gary Neal wrote: >Hello, > >Seems to work fine when the motor isn't connected to >the relay. Only resets when the motor is connected. Try this: use twisted wires going from the 12V supply to the relay, then from the relay to the motor. Put a 100n mono cap across the 12V supply right at the relay. In other words, add a bypass cap across the 12V supply just BEFORE the relay. Also use twisted wires from the relay to motor. You may also want to try putting a MOV across the motor leads, right at the motor. The idea here is to present a low AC impedance bypass to the noise right where it gets generated - right at the relay contacts. Putting a mono cap across the motor supply right at the relay means that the noise is mostly confined to the loop from the relay to the motor. Using twisted wires helps keep that noise contained to a small area. Adding a MOV right at the motor may help - it certainly does when the load is a large industrial contacter or solenoid. That huge, very fast spike that is generated when the control relay opens gets clamped to a level that is much more easily contained. The same idea may hold even if the load is a motor instead of a solenoid. Others may suggest putting small caps right across the relay contacts - this usually doesn't work for me. But you can try it. Stopping those nasty spikes is almost a black art. Even though I've been doing this for many years, it still often takes several attempts to get it right. dwayne Dwayne Reid <dwaynerKILLspamplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 17 years of Engineering Innovation (1984 - 2001) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

At 02:36 PM 8/28/01 -0400, you wrote: >Hello, > > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 150 mW >Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. This >relay is controlling a very small DC motor (~0.5amps). About 10% of the >time when this relay turns on/off, it resets the PIC. I've verified this >is what's happening. Seems to work fine when the motor isn't connected to >the relay. Only resets when the motor is connected. > I'm using PORTA.0 through a resistor to turn on a 2N4401 transistor that >then powers the relay coil. I have a 1N4004 diode across the relay >coil. I have two 0.1uf caps on the +5v to the PIC. > The +5v for the PIC is from a powered protoboard. The +12v for the >transistor and relay are from a +12v battery. The grounds of these two >power supplies are tied together. > Can anyone help me figure out what's going on and fix this? > Try a diode right across the motor terminals (assuming it only has to go in one direction). Obviously you want it to be reverse-biased normally. Make sure that your 12V ground is only tied to the 5V ground at a single point, and preferably away from the chip on the 5V side. What is /MCLR conected to? Preferably tie it to a low-impedance external BOR circuit or to Vdd. Connect a 10 nF capacitor from C to E on the 2N4401. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" EraseMEspeffspam_OUTTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

{Quote hidden}> Hello, > > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 > 150 mW > Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. > This relay is controlling a very small DC motor (~0.5amps). About 10% > of the time when this relay turns on/off, it resets the PIC. I've > verified this is what's happening. Seems to work fine when the motor > isn't connected to the relay. Only resets when the motor is > connected. > I'm using PORTA.0 through a resistor to turn on a 2N4401 > transistor that > then powers the relay coil. I have a 1N4004 diode across the relay > coil. I have two 0.1uf caps on the +5v to the PIC. > The +5v for the PIC is from a powered protoboard. The +12v > for the > transistor and relay are from a +12v battery. The grounds of these > two power supplies are tied together. > Can anyone help me figure out what's going on and fix this? > > Thanks, > > Gary Hi Gary, It may be worth trying a 1N4148 diode in place of the 1N4004, as it is much faster switching diode. All the suggestions so far have been good, so figure out which one fixes the problem and then add all the others as extra safeguards. That my 2 cents worth. Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: @spam@brent.brownKILLspamclear.net.nz -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Brent Since it only happens whaen the motor is connected I suggest you look again at your earthing and power supply arrangements. It sounds as if you're doing it nearly right with the 2 supplies. Is the motor supplied from the 12V also - a bit of filtering on the feed to the relay may assist. If you are not going to be reversing the motor a diode accross it may help also - particularly if it has field windings rather than perminant magnets. Overall, I'd suggest making sure the earths are tied at only one point, filtering the 12V to the relay using a 10ohm resistor and 100n cap and if possible filtering the motor supply with at least a small inductor / cap and possibly a diode as well. Richard P Brent Brown <brent.brown@CLE To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU AR.NET.NZ> cc: Sent by: pic Subject: Re: [PIC]: PIC reseting due to relays microcontroller discussion list <PICLIST@MITVMA. MIT.EDU> 29/08/01 08:52 Please respond to pic microcontroller discussion list {Quote hidden}> Hello, > > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 > 150 mW > Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. > This relay is controlling a very small DC motor (~0.5amps). About 10% > of the time when this relay turns on/off, it resets the PIC. I've > verified this is what's happening. Seems to work fine when the motor > isn't connected to the relay. Only resets when the motor is > connected. > I'm using PORTA.0 through a resistor to turn on a 2N4401 > transistor that > then powers the relay coil. I have a 1N4004 diode across the relay > coil. I have two 0.1uf caps on the +5v to the PIC. > The +5v for the PIC is from a powered protoboard. The +12v > for the > transistor and relay are from a +12v battery. The grounds of these > two power supplies are tied together. > Can anyone help me figure out what's going on and fix this? > > Thanks, > > Gary Hi Gary, It may be worth trying a 1N4148 diode in place of the 1N4004, as it is much faster switching diode. All the suggestions so far have been good, so figure out which one fixes the problem and then add all the others as extra safeguards. That my 2 cents worth. Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: spamBeGonebrent.brownspamBeGoneclear.net.nz -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservEraseMEspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Richard, just for the record, I wasn't the original poster. Good suggestions though. I once tried all these tricks on a small DC motor that was failing EMC compliance tests with not much luck The answer was a series inductor in each lead to the motor and ceramic caps to motor casing. {Quote hidden}> Brent > Since it only happens whaen the motor is connected I suggest you look > again at your earthing and power supply arrangements. It sounds as if > you're doing it nearly right with the 2 supplies. Is the motor > supplied from the 12V also - a bit of filtering on the feed to the > relay may assist. If you are not going to be reversing the motor a > diode accross it may help also - particularly if it has field windings > rather than perminant magnets. > > Overall, I'd suggest making sure the earths are tied at only one > point, filtering the 12V to the relay using a 10ohm resistor and 100n > cap and if possible filtering the motor supply with at least a small > inductor / cap and possibly a diode as well. > > Richard P Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: brent.brownEraseME.....clear.net.nz -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

Guys, Just wanted to give some feedback on all the suggestions that have been submitted. BTW, there have been a lot of suggestions. I appreciate it a lot. I went through the suggestions and tried them. Listed below is what I tried and how well it worked. 1. 0.1uf cap across relay coil - no help 2. 4.7ohm resistor in series with relay coil - no help 3. Checking all inputs for noise or floating inputs - no help 4. 10nf cap from C to E on the transistor - no help 5. Put 0.1uf cap across relay contacts - partial success. Instead of failing like 75% of the time, it only failed about 10% of the time 6. Put two 0.1 uf caps across relay contacts (in parallel) - better partial success. Failed probably 5% of the time. 7. Moved the caps to the terminals right on the motor - better success. Failed probably 1% of the time. I'm saying failure is when the PIC resets or jumps to a random place in the code. So, I'm thinking if I put a bigger cap on the motor winding terminals, it will help even more. Question is, how big of a cap should I use? I can't use an electrolytic b/c the motor reverses direction. Anyone have a suggestion? Hopefully something fairly cheap. Thanks, Gary At 02:55 PM 8/28/01 -0400, Dan Michaels wrote: {Quote hidden}>Gary Neal wrote: > >Hello, > > > > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 150 mW > >Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. This > >relay is controlling a very small DC motor (~0.5amps). About 10% of the > >time when this relay turns on/off, it resets the PIC. I've verified this > >is what's happening. Seems to work fine when the motor isn't connected to > >the relay. Only resets when the motor is connected. >....... > > >Sounds like you need a suppressor across the relay "contacts", or >better yet at the motor itself. Since a DC motor, try a reverse >diode there or a snubber - 10-100 ohm resistor in series with a >0.1 uF cap across the motor winding. The cap should be better >quality than simple low-V ceramic. 200V or so polypropylene. > >- dan michaels >http://www.oricomtech.com >======================== > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email RemoveMElistservEraseMEEraseMEmitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu

Gary Neal wrote: > 7. Moved the caps to the terminals right on the motor - better > success. Failed probably 1% of the time. > > I'm saying failure is when the PIC resets or jumps to a random > place in the code. > So, I'm thinking if I put a bigger cap on the motor winding > terminals, it will help even more. Question is, how big of a cap should I > use? I can't use an electrolytic b/c the motor reverses direction. Anyone > have a suggestion? Hopefully something fairly cheap. We in the electric R/C world always put caps on the terminals (10n). What we also do is to connect a cap from each terminal to the metal body of the motor as well. Quentin -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu

I think you are getting closer to the solution. You've shown that working at the motor seems to help the most. Remember that bigger capacitors that are rolled or folded inside have an inductance, meaning that sometimes smaller simpler capacitors can bypass the highest frequencies better. In some cases a combination is warranted. Don't just keep making the caps bigger, try some of the other ideas in addition to the caps. Barry At 02:05 PM 8/29/01 -0400, you wrote: {Quote hidden}>Guys, > > Just wanted to give some feedback on all the suggestions that have >been submitted. BTW, there have been a lot of suggestions. I appreciate >it a lot. > I went through the suggestions and tried them. Listed below is >what I tried and how well it worked. > >1. 0.1uf cap across relay coil - no help >2. 4.7ohm resistor in series with relay coil - no help >3. Checking all inputs for noise or floating inputs - no help >4. 10nf cap from C to E on the transistor - no help >5. Put 0.1uf cap across relay contacts - partial success. Instead of >failing like 75% of the time, it only failed about 10% of the time >6. Put two 0.1 uf caps across relay contacts (in parallel) - better >partial success. Failed probably 5% of the time. >7. Moved the caps to the terminals right on the motor - better >success. Failed probably 1% of the time. > > I'm saying failure is when the PIC resets or jumps to a random >place in the code. > So, I'm thinking if I put a bigger cap on the motor winding >terminals, it will help even more. Question is, how big of a cap should I >use? I can't use an electrolytic b/c the motor reverses direction. Anyone >have a suggestion? Hopefully something fairly cheap. > >Thanks, > >Gary > > >At 02:55 PM 8/28/01 -0400, Dan Michaels wrote: >>Gary Neal wrote: >> >Hello, >> > >> > I've got a 16f870 that I'm using to turn a relay (Tyco V23105 150 mW >> >Nominal Coil Power, 960 ohm, 12 volt Nominal Coil Voltage) on/off. This >> >relay is controlling a very small DC motor (~0.5amps). About 10% of the >> >time when this relay turns on/off, it resets the PIC. I've verified this >> >is what's happening. Seems to work fine when the motor isn't connected to >> >the relay. Only resets when the motor is connected. >>....... >> >> >>Sounds like you need a suppressor across the relay "contacts", or >>better yet at the motor itself. Since a DC motor, try a reverse >>diode there or a snubber - 10-100 ohm resistor in series with a >>0.1 uF cap across the motor winding. The cap should be better >>quality than simple low-V ceramic. 200V or so polypropylene. >> >>- dan michaels >>http://www.oricomtech.com >>======================== >> >>-- >>http://www.piclist.com#nomail Going offline? Don't AutoReply us! >>email EraseMElistservspamspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body > >-- >http://www.piclist.com hint: To leave the PICList >RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu > > > > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestSTOPspamspam_OUTmitvma.mit.edu

Gary Neal wrote: ........... >7. Moved the caps to the terminals right on the motor - better >success. Failed probably 1% of the time. > Good to hear things are coming along. You might try small R's [10-100 ohms] in series with the caps, since you will get a current surge into the cap during relay contact closure otherwise. You get L di/dt [from motor] at contact opening and C dv/dt [from cap] at closure. Also, as others mentioned, if the caps are too big the sol'n is self-defeating due to series inductance/etc. Effective snubbers for switching "amp" loads at 220VAC usually use no more than 0.1 uF or so - but they usually have series R's too. If using separate motor gnds and also snubber at the motor doesn't do the trick, then you may need to go in and strenghten spike rejection circuitry throughout the entire conotroller. I have been involved in this sort of thing, and sometimes it takes appropriate components placed in "many" places before the system is reliable. BTW, are your current 1% failures occurring at relay "closure" or "opening" ????? - dan michaels http://www.oricomtech.com ======================== -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestSTOPspamEraseMEmitvma.mit.edu

Jinx, I noticed that you do not have a series resistor into the MCLR pin when using a capacitor like Mchip suggests. Not sure I actually understand their reasoning on this anyway, any comments? > A couple of people asked me off-list what I meant. Attached > is a gif from my notes at the time. The opto and motor caps > were already built in to the ticket mechanism. It also had an > opto for the inter-ticket holes which the PIC used for counting Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: @spam@brent.brown@spam@spam_OUTclear.net.nz -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestKILLspammitvma.mit.edu

> 1. 0.1uf cap across relay coil - no help > 2. 4.7ohm resistor in series with relay coil - no help > 3. Checking all inputs for noise or floating inputs - no help > 4. 10nf cap from C to E on the transistor - no help > 5. Put 0.1uf cap across relay contacts - partial success. Instead of > failing like 75% of the time, it only failed about 10% of the time > 6. Put two 0.1 uf caps across relay contacts (in parallel) - better > partial success. Failed probably 5% of the time. > 7. Moved the caps to the terminals right on the motor - better > success. Failed probably 1% of the time. > > I'm saying failure is when the PIC resets or jumps to a random > place in the code. > So, I'm thinking if I put a bigger cap on the motor winding > terminals, it will help even more. Question is, how big of a cap should I > use? I can't use an electrolytic b/c the motor reverses direction. Anyone > have a suggestion? Hopefully something fairly cheap. Trying to reduce the noise at the source like you are doing is reasonable. However, you should also try to make your circuit immune to the noise. Make sure you have a good ground plane under the PIC and put bypass caps as close as possible to each power lead. It sounds like high frequency noise is making it back to your 5V power supply. You may also have a ground spike between the PIC and wherever its I/O lines are going. In that case, beaf up the ground conductor and put small series resistor on the PIC lines. To go further, you could also put some clamping on the lines. Whether this is acceptable depends partially on whether you can tolerate slower edeges and what the lines are driving, etc. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, .....olinspam_OUTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-request.....TakeThisOuTmitvma.mit.edu

At 12:00 PM 8/30/01 +1200, you wrote: >A couple of people asked me off-list what I meant. Attached >is a gif from my notes at the time. The opto and motor caps >were already built in to the ticket mechanism. It also had an >opto for the inter-ticket holes which the PIC used for counting > >Attachment Converted: C:\WIN31APP\EUDORA\ATTACH\ticket.gif > I hate to be a poop, Captain.J, but you are not supposed to tie a big cap straight into the /Mclr pin. [need I explain?] -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I hate to be a poop, Only you know that for sure. Pick one for your conscience (a) Dan Michaels = A damn chisel (b) I'm Dan Michaels = A calm dim shine Try it with mine (ha ha, good luck with the J and Q) > but you are not supposed to tie a big cap straight into > the /Mclr pin Is 1uF really that big ? I recall others on the list who routinely use 10uF or more with no apparent problem. As I said, my usual is 10n + 10k [need I explain?] ooookay, you got some 'splainin' to do Lucy -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Is 1uF really that big ? Yes, I definitely wouldn't do this. When power is shut off and the power supply drops, the cap will discharge thru the PIC. The cap current is I = C * dV/dt = 1uF * 5V / Td, where Td is the power supply discharge time in seconds. If your supply discharges in 5mS then the average cap current will be 1mA. If the PIC doesn't allow that current, then you enter unspecified territory with MCLR at 5V and everything else at 0. > I recall others on the list who routinely > use 10uF or more with no apparent problem. Now you get 1mA average at 50mS discharge time. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, TakeThisOuTolinKILLspamspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> A couple of people asked me off-list what I meant. Attached > is a gif from my notes at the time. The opto and motor caps > were already built in to the ticket mechanism. It also had an > opto for the inter-ticket holes which the PIC used for counting I noticed the motor is used in one direction only but has no flyback diode around it. This may have been part of what was causing your glitches. The 100nF caps slow down and reduce the peak voltage of the flyback pulse, but I think the transistor is still taking a beating. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, .....olinRemoveMEembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

At 12:36 PM 8/30/01 -0400, you wrote: >Note that if you accidentally short the power supply by dropping a >screwdriver on it, the dV/dt will be very high. Yes. Whether you wish to cover that case by adding extra parts is probably application-specific. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" RemoveMEspeffspamBeGoneinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> > opto for the inter-ticket holes which the PIC used for counting > > I noticed the motor is used in one direction only but has no > flyback diode around it. This may have been part of what > was causing your glitches. The 100nF caps slow down and > reduce the peak voltage of the flyback pulse, but I think the > transistor is still taking a beating I couldn't swear to the fact there was no flyback diode. The dispenser was a ready-made module and I made the best notes I could without dismantling it. Aside from that though, the carnival game this was part of was a rifle range using flash tubes in the guns. A trigger-operated circuit dumped 450VDC into the flash tubes, which caused quite an electronic ruckus. So even if the motor had been clean, the micro still needed protecting -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> > > Is 1uF really that big ? > > > > Yes, I definitely wouldn't do this > > OK, I'm sold. From now on I'll add series R. The F87x pdf > I have has no circuit suggestion and no special comments > about Mclr (that I can see anyway). Is it the same as the > F84A ? In the F87x case I suspect the ICD might have problems with a cap on MCLR. Can't say why exactly, just a gut feeling... Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: spamBeGonebrent.brown@spam@spam_OUTclear.net.nz -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Get the latest d/s, see fig 12-6 - [fig missing from 1st > d/s, present in last 2 versions]. The Reset section of the mid-range manual is more up-to-date than the specific F628 manual I got not all that long ago. It does make some points not in older references, but the full story still isn't there in one place. Sheesh. Still, what the hell www.microchip.com/0/lit/pline/picmicro/refernce/midrange/midsect/3100 3a/index.htm "Better be ignorant of a matter than half know it" - Plubilius Syrius -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 06:09 PM 8/31/01 +1200, you wrote: >> Get the latest d/s, see fig 12-6 - [fig missing from 1st >> d/s, present in last 2 versions]. > >The Reset section of the mid-range manual is more >up-to-date than the specific F628 manual I got not all >that long ago. It does make some points not in older >references, but the full story still isn't there in one place. >Sheesh. Still, what the hell > >www.microchip.com/0/lit/pline/picmicro/refernce/midrange/midsect/3100 >3a/index.htm > >"Better be ignorant of a matter than half know it" - Plubilius Syrius > If you're speaking of the basic info re weakness at the /Mclr pin in PICs, it is present in my '95 Mchp databook. It just happened to be left out of the "1st" version of the 'F87x d/s, but is present in later versions. Mchp has known of this issue for years. The figure also is left out of 'F628 d/s I have dated 12/09/99. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics