CA Zuke wrote:>> So, you need to pick a power source, either battery or regulator that: >> >> a) provides a voltage suitable for the pic >> >> b) is capable of providing at least the amount of current the pic >> requires. >> >> AFAIK pics require only a few tens of milliamps current so a 78L05 or >> your batteries should be fine. >> >> HTH >> >> Ian > > So does that mean that the current of the power source can never break > a pic? Because the pic only takes the amount of power it needs? That > sounds strange... Does that mean if I have a pic connected to one led, > and I give it 10A that everything will work properly if the Voltage is > within the specifications of the pic?Yes. You cannot 'give it 10A'. If you connect the correct voltage to it then it will take whatever current it needs. The current rating of a regulated voltage power supply for example only tells you how much current it *can* supply if the load demands it. This is not strange but a simple consequence of ohms law which can be expressed as: I = V/R Where I is the load current, V is the applied voltage and R the load resistance. The PIC effectively has a certain value of R. When you apply a voltage V it is the above formula gives the current. The PIC will only take more current if you increase the voltage. Ian -- Ian Bell
Pic Currrent
Started by ●October 15, 2004
Reply by ●October 18, 20042004-10-18
Reply by ●October 18, 20042004-10-18
CA Zuke <ceauke@yahoo.com> wrote: [...]> So does that mean that the current of the power source can never break > a pic? Because the pic only takes the amount of power it needs?Whoa, Silver! Let's stop right here, for a little consideration. Now, how do I put this politely...: you're in *desparate* need of some very basic education about how electricity works. I strongly advise you stop thinking about microprocessors for a while and go back to lamps, batteries, switches, and maybe some resistors. Learn how they actually behave, learn Ohm's law, Kirchhoff's node and loop rules, and what the symbols in an electronics schematic actually mean. -- Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.
Reply by ●October 18, 20042004-10-18
Meindert Sprang <mhsprang@nocustomspamware.nl> wrote:> "CA Zuke" <ceauke@yahoo.com> wrote in message > news:ff8b1683.0410180038.1e8c54b3@posting.google.com... > > So does that mean that the current of the power source can never break > > a pic? Because the pic only takes the amount of power it needs? That > > sounds strange... Does that mean if I have a pic connected to one led, > > and I give it 10A that everything will work properly if the Voltage is > > within the specifications of the pic?> I think you don't quite understand how this works. You don't *give* > something a current, you apply a voltage. And the devices that gets the > voltage determines how much current it draws from the voltage source.<Nitpick> Or you apply a current, and the device determines how much voltage you have to supply to get that current through it. Devices known as "constant current sources" aren't exactly the typical case, sure, but they do exist. Many households have one these days, known to the laypersons as a (simplistic version of a) battery charger. </Nitpick> -- Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.
Reply by ●October 18, 20042004-10-18
On Mon, 18 Oct 2004 10:48:01 +0100, the renowned Ian Bell <ruffrecords@yahoo.com> wrote:>CA Zuke wrote: > >>> So, you need to pick a power source, either battery or regulator that: >>> >>> a) provides a voltage suitable for the pic >>> >>> b) is capable of providing at least the amount of current the pic >>> requires. >>> >>> AFAIK pics require only a few tens of milliamps current so a 78L05 or >>> your batteries should be fine. >>> >>> HTH >>> >>> Ian >> >> So does that mean that the current of the power source can never break >> a pic? Because the pic only takes the amount of power it needs? That >> sounds strange... Does that mean if I have a pic connected to one led, >> and I give it 10A that everything will work properly if the Voltage is >> within the specifications of the pic? > >Yes. You cannot 'give it 10A'.Well, you *could*, with a CC supply... A little inaccuracy sometimes saves tons of explanation. --Saki (1870 - 1916) Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●October 18, 20042004-10-18
CA Zuke wrote:>>So, you need to pick a power source, either battery or regulator that: >> >>a) provides a voltage suitable for the pic >> >>b) is capable of providing at least the amount of current the pic requires. >> >>AFAIK pics require only a few tens of milliamps current so a 78L05 or your >>batteries should be fine. >> >>HTH >> >>Ian > > > So does that mean that the current of the power source can never break > a pic? Because the pic only takes the amount of power it needs? That > sounds strange... Does that mean if I have a pic connected to one led, > and I give it 10A that everything will work properly if the Voltage is > within the specifications of the pic?Think of electricity as water. If you raise a bucket of water 2 meters, then that's voltage. If you attach a hose to the bottom of the bucket, that the hose is your PIC and the water running through it is the current. As you can probably picture in this (flawed) analogy, if you have a much wider pipe, more "current" can flow. As with the bucket, you "apply" a voltage (the height to which you raise it) and the current (the amount of water running through it) is a function of the size of the pipe (impedence). You might find this http://www.ibiblio.org/obp/electricCircuits/ interesting and useful. It's a free online textbook about electric circuits and electricity. You'll find that your PIC experiments will be much more sucessful and rewarding if you pause for a bit to get some of the basics. Even if you only read through chapters 1-3, you'll get a lot. Ed
Reply by ●October 18, 20042004-10-18
"Hans-Bernhard Broeker" <broeker@physik.rwth-aachen.de> wrote in message news:2thlbdF1urnn1U5@uni-berlin.de...> <Nitpick> Or you apply a current, and the device determines how much > voltage you have to supply to get that current through it. Devices > known as "constant current sources" aren't exactly the typical case, > sure, but they do exist. Many households have one these days, known > to the laypersons as a (simplistic version of a) battery > charger. </Nitpick>I know they exist, but I didn't want to throw that on him too, because it would have contributed heavily to the confusion, I think :-) Meindert
Reply by ●October 18, 20042004-10-18
"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> schreef in bericht news:fc57n0lnlab11ddtkocvdvm4cbglm79072@4ax.com...> On Mon, 18 Oct 2004 10:48:01 +0100, the renowned Ian Bell > <ruffrecords@yahoo.com> wrote: > > >CA Zuke wrote: > > > >>> So, you need to pick a power source, either battery or regulator that: > >>> > >>> a) provides a voltage suitable for the pic > >>> > >>> b) is capable of providing at least the amount of current the pic > >>> requires. > >>> > >>> AFAIK pics require only a few tens of milliamps current so a 78L05 or > >>> your batteries should be fine. > >>> > >>> HTH > >>> > >>> Ian > >> > >> So does that mean that the current of the power source can never break > >> a pic? Because the pic only takes the amount of power it needs? That > >> sounds strange... Does that mean if I have a pic connected to one led, > >> and I give it 10A that everything will work properly if the Voltage is > >> within the specifications of the pic? > > > >Yes. You cannot 'give it 10A'. > > > Well, you *could*, with a CC supply...Sort of last hack, if it won't run? I am ashamed to admit that I actually did that once ;) -- Thanks, Frank. (remove 'x' and 'invalid' when replying by email)
Reply by ●October 18, 20042004-10-18
On Mon, 18 Oct 2004 13:09:39 +0200, the renowned "Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> wrote:>"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> schreef in bericht >news:fc57n0lnlab11ddtkocvdvm4cbglm79072@4ax.com... >> On Mon, 18 Oct 2004 10:48:01 +0100, the renowned Ian Bell >> <ruffrecords@yahoo.com> wrote: >> >> >CA Zuke wrote: >> > >> >>> So, you need to pick a power source, either battery or regulator that: >> >>> >> >>> a) provides a voltage suitable for the pic >> >>> >> >>> b) is capable of providing at least the amount of current the pic >> >>> requires. >> >>> >> >>> AFAIK pics require only a few tens of milliamps current so a 78L05 or >> >>> your batteries should be fine. >> >>> >> >>> HTH >> >>> >> >>> Ian >> >> >> >> So does that mean that the current of the power source can never break >> >> a pic? Because the pic only takes the amount of power it needs? That >> >> sounds strange... Does that mean if I have a pic connected to one led, >> >> and I give it 10A that everything will work properly if the Voltage is >> >> within the specifications of the pic? >> > >> >Yes. You cannot 'give it 10A'. >> >> >> Well, you *could*, with a CC supply... > >Sort of last hack, if it won't run? > >I am ashamed to admit that I actually did that once ;)Or accidentally turn the voltage up on a bench supply until it hits the CC limit. Stuff happens. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●October 18, 20042004-10-18
Meindert Sprang wrote:> "Hans-Bernhard Broeker" <broeker@physik.rwth-aachen.de> wrote in message > >> <Nitpick> Or you apply a current, and the device determines how much >> voltage you have to supply to get that current through it. Devices >> known as "constant current sources" aren't exactly the typical case, >> sure, but they do exist. Many households have one these days, known >> to the laypersons as a (simplistic version of a) battery >> charger. </Nitpick> > > I know they exist, but I didn't want to throw that on him too, because > it would have contributed heavily to the confusion, I think :-)Don't forget Van de Graffe machines, which have a much higher voltage compliance range than the common tufted battery charger :-) -- "I support the Red Sox and any team that beats the Yankees" "Any baby snookums can be a Yankee fan, it takes real moral fiber to be a Red Sox fan"
Reply by ●October 18, 20042004-10-18
Spehro Pefhany wrote:> On Mon, 18 Oct 2004 10:48:01 +0100, the renowned Ian Bell > <ruffrecords@yahoo.com> wrote: > >>CA Zuke wrote: >> >>>> So, you need to pick a power source, either battery or regulator that: >>>> >>>> a) provides a voltage suitable for the pic >>>> >>>> b) is capable of providing at least the amount of current the pic >>>> requires. >>>> >>>> AFAIK pics require only a few tens of milliamps current so a 78L05 or >>>> your batteries should be fine. >>>> >>>> HTH >>>> >>>> Ian >>> >>> So does that mean that the current of the power source can never break >>> a pic? Because the pic only takes the amount of power it needs? That >>> sounds strange... Does that mean if I have a pic connected to one led, >>> and I give it 10A that everything will work properly if the Voltage is >>> within the specifications of the pic? >> >>Yes. You cannot 'give it 10A'. > > > Well, you *could*, with a CC supply... > > A little inaccuracy sometimes saves tons of explanation. > --Saki (1870 - 1916)I was quite conscious of the several inaccuracies in my reply but I felt that, given the OPs obvious lack of basic electronics knowledge, further detail would only confuse him. I'm with you and Saki on this one. Ian> > > > Best regards, > Spehro Pefhany-- Ian Bell