Post by thread:[EE]: PIC in an automotive circuit/voltage regulat

Hi All, i'm developing a pic based automotive electronic ignition, it's based on a mc10012 darlington as the main coil switch, a very low value resistance for current feedback/sensing and a pic for controlling the dwell angle at various rpm. in paper and in my desk works well, but i think that the voltage regulator must be a little more than a 7805, so, where i can find information (or schematics) for build a reliable voltage regulator?, and what precautions i must follow to minimize noise, etc? (it's for a jeep, and i don't want the motor to stall climbing a hill) any help will be great! thanks RVP. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

This was forgotten from the original message: i know that i must use a low dropout voltage regulator for automotive applications (i have a couple of lm2940 for this project), i'm worry about others components (capacitors, inductances, zenners, etc) that will help to keep noise away from the pic. remember that in the other side of the pic i have a hv coil, with one terminal on the 12v of the battery. thanks again. RVP. Rodrigo Valladares P. wrote: {Quote hidden}> Hi All, > > i'm developing a pic based automotive electronic ignition, it's based on > a mc10012 darlington as the main coil switch, a very low value > resistance for current feedback/sensing and a pic for controlling the > dwell angle at various rpm. in paper and in my desk works well, but i > think that the voltage regulator must be a little more than a 7805, so, > where i can find information (or schematics) for build a reliable > voltage regulator?, and what precautions i must follow to minimize > noise, etc? (it's for a jeep, and i don't want the motor to stall > climbing a hill) > > any help will be great! > > thanks > > RVP. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

I use the National LM2931 series of low dropout voltage regulators in marine engine applications. There is an adjustable version, plus a 5 volt foxed version. These are designed for automotive applications, where transient voltages on the battery can be quite high. Check it out in the National Semi web site http://www.national.com/design/index.html As to noise - filter, filter, filter. Use an RC filter on all inputs from sensors - the values will depend on the expected rate-of-change of the sensor data. I tend to use a 1K resistor and a 10uf capacitor with a 0.1 uf capacitor in parallel on all input signals in "slowly changing" systems. Tie all unused inputs to ground. Use a filter on the 12V input (before the regulator) to help keep noise out of the power supply. Don't use the automotive ground for sensor return if you can help it. For example, if you have a series resistor (shunt) to measure current, use a 4-wire connection for the shunt - connect it in the circuit to be measured with the normal leads, then connect two more wires to the resistor closer to the resistor body than the normal leads to use as your sensor wires. Then use an opamp in a differential configuration connected to the sense wires (if you need more info on this get back to me) to help eliminate noise on the sensor wires. Use a separate wire for the emitter of the switching transistor - don't just use the negative supply line to your PIC circuit. Connect this wire to ground at the engine block, or some such ground point. You don't want the switching current going through the negative supply line to the PIC - nasty spikes. I'd even be tempted to mount the switching transistor close to the coil, rather than as a part of the PIC circuitry, and just feed the base drive voltage to it from the PIC - again, with a filter on this lead - the filter values probably need to be smaller than 1k/10uf since the filter will effect the rise time of the switching pulse. And you might think about building it in a metal box, rather than a plastic one. Have fun! Larry At 02:56 AM 1/7/2003 -0400, you wrote: {Quote hidden}>Hi All, > >i'm developing a pic based automotive electronic ignition, it's based on >a mc10012 darlington as the main coil switch, a very low value >resistance for current feedback/sensing and a pic for controlling the >dwell angle at various rpm. in paper and in my desk works well, but i >think that the voltage regulator must be a little more than a 7805, so, >where i can find information (or schematics) for build a reliable >voltage regulator?, and what precautions i must follow to minimize >noise, etc? (it's for a jeep, and i don't want the motor to stall >climbing a hill) > >any help will be great! > >thanks > >RVP. > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads Larry Bradley -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads Orleans (Ottawa), Ontario, CANADA

thanks larry, i will follow word by word all your advice, really lots of fun awaits me RVP. Larry Bradley wrote: {Quote hidden}> I use the National LM2931 series of low dropout voltage regulators in > marine engine applications. There is an adjustable version, plus a 5 volt > foxed version. These are designed for automotive applications, where > transient voltages on the battery can be quite high. Check it out in the > National Semi web site > > http://www.national.com/design/index.html > > > As to noise - filter, filter, filter. Use an RC filter on all inputs from > sensors - the values will depend on the expected rate-of-change of the > sensor data. I tend to use a 1K resistor and a 10uf capacitor with a > 0.1 uf > capacitor in parallel on all input signals in "slowly changing" systems. > Tie all unused inputs to ground. > > Use a filter on the 12V input (before the regulator) to help keep > noise out > of the power supply. > > Don't use the automotive ground for sensor return if you can help it. For > example, if you have a series resistor (shunt) to measure current, use a > 4-wire connection for the shunt - connect it in the circuit to be > measured > with the normal leads, then connect two more wires to the resistor closer > to the resistor body than the normal leads to use as your sensor wires. > Then use an opamp in a differential configuration connected to the sense > wires (if you need more info on this get back to me) to help eliminate > noise on the sensor wires. > > Use a separate wire for the emitter of the switching transistor - don't > just use the negative supply line to your PIC circuit. Connect this > wire to > ground at the engine block, or some such ground point. You don't want the > switching current going through the negative supply line to the PIC - > nasty > spikes. I'd even be tempted to mount the switching transistor close to > the > coil, rather than as a part of the PIC circuitry, and just > feed the base drive voltage to it from the PIC - again, with a filter on > this lead - the filter values probably need to be smaller than 1k/10uf > since the filter will effect the rise time of the switching pulse. > > And you might think about building it in a metal box, rather than a > plastic > one. > > Have fun! > > Larry > > At 02:56 AM 1/7/2003 -0400, you wrote: > >> Hi All, >> >> i'm developing a pic based automotive electronic ignition, it's based on >> a mc10012 darlington as the main coil switch, a very low value >> resistance for current feedback/sensing and a pic for controlling the >> dwell angle at various rpm. in paper and in my desk works well, but i >> think that the voltage regulator must be a little more than a 7805, so, >> where i can find information (or schematics) for build a reliable >> voltage regulator?, and what precautions i must follow to minimize >> noise, etc? (it's for a jeep, and i don't want the motor to stall >> climbing a hill) >> >> any help will be great! >> >> thanks >> >> RVP. >> >> -- >> http://www.piclist.com hint: PICList Posts must start with ONE topic: >> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > Larry Bradley > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > Orleans (Ottawa), Ontario, CANADA > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

To be honest, I don't know. I bought some JW versions as well as some OTP's for an automotive product, but didn't get around to doing anything yet. I think they were designed with automotive functions in mind, but don't know for sure! Howard At 01:07 AM 1/8/2003 -0400, you wrote: {Quote hidden}>Hi, > >i have to deal with small stores of electronic components, so i don't >have access to all the pic micro family, do you know how well this >device will be in an hostile environment? > >thanks > >Howard McGinnis wrote: > >>Have you considered the 16HV540? It shouldn't need the regulator, however >>it's not a flash part and lacks EE. >> >>Howard >> >>-- >>http://www.piclist.com hint: PICList Posts must start with ONE topic: >>[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads Howard McGinnis Electronic Visions, Inc. spam_OUTmcginnisTakeThisOuTe-visions.com http://www.e-visions.com -- 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 01:31 PM 1/8/03 -0500, you wrote: >To be honest, I don't know. I bought some JW versions as well as some OTP's >for an automotive product, but didn't get around to doing anything yet. I >think they were designed with automotive functions in mind, but don't know >for sure! They seem to have been, but they also seem to be orphaned chips, with only a single member in the family, like the PIC14000. Automotive supplies have a lot of nasty transients, check the relevant standards for the exact requirements, but +/-24V 5 minutes jump start, and 125V 200-500ms 10J load dump, and the 300V-80V 1J 320usec inductive transients, -100V 1J alternator field decay etc (at each shut off), etc. I think the standards are something like ISO 7637 and SAE J1113. It's not hard to meet them if your circuit just draws a bit of current, you just put lots of series impedance and a hefty shunt zener or TVS in there. Some regulators like the LM2940 have *some* protection built-in but be careful about the output capacitor, they are only stable for some values and some ESRs. If your cap is too big, too lousy, too small or too *good* you get an oscillator. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam@spam@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- 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

The LM2941 series are designed as automotive regulators - they handle reverse polarity, load dump - take a look at the National web site. I've been using one in a PIC-based circuit on my sailboat which has an ancient old gasoline engine - so far so good. It too is a low-dropout regulator, requiring a hefty low ESR (read tantalum) capacitor - they recommend 47uf or more - I use 2x47 uf tantalum in parallel. Larry At 04:26 PM 1/8/2003 -0500, you wrote: {Quote hidden}>At 01:31 PM 1/8/03 -0500, you wrote: >>To be honest, I don't know. I bought some JW versions as well as some OTP's >>for an automotive product, but didn't get around to doing anything yet. I >>think they were designed with automotive functions in mind, but don't know >>for sure! > >They seem to have been, but they also seem to be orphaned chips, with only >a single member in the family, like the PIC14000. > >Automotive supplies have a lot of nasty transients, check the relevant >standards for the exact requirements, but +/-24V 5 minutes jump start, >and 125V 200-500ms 10J load dump, and the 300V-80V 1J 320usec inductive >transients, -100V 1J alternator field decay etc (at each shut off), etc. >I think the standards are something like ISO 7637 and SAE J1113. > >It's not hard to meet them if your circuit just draws a bit of current, >you just put lots of series impedance and a hefty shunt zener or TVS >in there. Some regulators like the LM2940 have *some* protection built-in >but be careful about the output capacitor, they are only stable for >some values and some ESRs. If your cap is too big, too lousy, too small >or too *good* you get an oscillator. > >Best regards, > >Spehro Pefhany --"it's the network..." "The Journey is the reward" >speffKILLspaminterlog.com Info for manufacturers: http://www.trexon.com >Embedded software/hardware/analog Info for designers: http://www.speff.com > >-- >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 Larry Bradley Orleans (Ottawa), Ontario, CANADA -- 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