Post by thread:[PIC] Looking for simple way to use PIC to measure

I am working on a project where I need to measure current for voltages 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. I would prefer a low cost method as this is just a hobby project not something for production. It doesn't need to be terribly accurate, within a couple hundred ma would be fine. I have pics 18f4580 , 18f2580, 16f88 and a few others to work with. Thanks Mark

Current sense resistor, current sense amplifier (LT makes some nice ones, I think maxim has some that you might be able to sample), PIC ADC input. On Mon, May 31, 2010 at 2:35 PM, Mark <spam_OUTmarkTakeThisOuTcgmark.us> wrote: > I am working on a project where I need to measure current for voltages > 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. > I would prefer a low cost method as this is just a hobby project not > something for production. It doesn't need to be terribly accurate, > within a couple hundred ma would be fine. > I have pics 18f4580 , 18f2580, 16f88 and a few others to work with. > > Thanks > Mark > -

> I am working on a project where I need to measure current for voltages > 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. > I would prefer a low cost method as this is just a hobby project not > something for production. It doesn't need to be terribly accurate, > within a couple hundred ma would be fine. - Linear Hall cell monitoring field from wire. - DC Shunt and measure mV. Nees to be LOW resistance to keep power loss down. eg ~ 1 Watt per 15 mV at 60 A. Note that 200 mA at 60 A = 1 part in 300 = > 8 bits - so "not terribly accurate" only works for some values of terribly. Russell

Em 31/5/2010 09:52, Marcel Birthelmer escreveu: > Current sense resistor, current sense amplifier (LT makes some nice > ones, I think maxim has some that you might be able to sample), PIC > ADC input. > > On Mon, May 31, 2010 at 2:35 PM, Mark <.....markKILLspam@spam@cgmark.us> wrote: > >> I am working on a project where I need to measure current for voltages >> 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. >> I would prefer a low cost method as this is just a hobby project not >> something for production. It doesn't need to be terribly accurate, >> within a couple hundred ma would be fine. >> I have pics 18f4580 , 18f2580, 16f88 and a few others to work with. >> >> Thanks >> Mark >> But at 60A he will need a very low value for the sense resistor (1 mOhm will dissipate 3.6W), and a very good amplifier circuit. Perhaps he could use off-the-shelf Hall Effect current probes. Regards, Isaac __________________________________________________ Fale com seus amigos de graça com o novo Yahoo! Messenger http://br.messenger.yahoo.com/

>I am working on a project where I need to measure current for voltages > 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A One of the few Silicon Chip articles that are available fully on-line 0-80A ammeter http://www.siliconchip.com.au/cms/A_30551/article.html 16F84 based, using the old firmware ADC method. Would be a snip to convert for a PIC that has hardware ADC, and probably more accurate too Joe

Mark wrote: > I am working on a project where I need to measure current for voltages > 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. > I would prefer a low cost method as this is just a hobby project not > something for production. It doesn't need to be terribly accurate, > within a couple hundred ma would be fine. > I have pics 18f4580 , 18f2580, 16f88 and a few others to work with. There are lots of ways to do this, each with its own difficulties. How about a small coil and Hall sensor? That gets around high side / low side measurement issues and is totally isolated? Adjust coil turns to get desired full scale range by experiment. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000.

> Mark wrote: >> I am working on a project where I need to measure current for voltages >> 5V, 3.3V, 12V all DC voltages and some have currents as high as 60A. >> I would prefer a low cost method as this is just a hobby project not >> something for production. It doesn't need to be terribly accurate, >> within a couple hundred ma would be fine. >> I have pics 18f4580 , 18f2580, 16f88 and a few others to work with. > > There are lots of ways to do this, each with its own difficulties. > > How about a small coil and Hall sensor? That gets around high side / low > side measurement issues and is totally isolated? Adjust coil turns to get > desired full scale range by experiment. I am certainly on the side of hall Sensor chips for this level of current. My choice would be one of the nice chips from Allegro Micro. See http://www.allegromicro.com/en/Products/Categories/Sensors/currentsensor.asp to make your selection. Note that the current sense wire can be either a track on the PCB (although I suspect this will not be heavy enough for 60A) or a wire over the top of the chip body (my preferred method at this current). Some models have a sense 'wire' built in, but it is still a PCB connection, and I seriously doubt the current capability of a track unless you don't worry about the voltage drop.