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Tue, 15 Apr 2014 12:20:54 -0700 (PDT) | |
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Subject: | Re: [geda-user] printed meter shunts |
From: | Nathan Stewart <therealnathanstewart AT gmail DOT com> |
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--047d7bfcfc62e0143604f719b24a Content-Type: text/plain; charset=ISO-8859-1 Why does it need to be TO-220? 3W wire shunt is about 50 cents. On Tue, Apr 15, 2014 at 2:54 PM, Richard Bown <richard AT g8jvm DOT com> wrote: > Hi, > I thinking of playing with the LTC1645 using its for over current shut > down, > it requires only 50mV across a shunt resistor to trip, at 10A thats > 5milli ohm. > And those resistors in TO-220 packages are expensive, so I was thinking > why use a length of wide track, needs to wide as handling up to 10A . > Are there any tables to give track resistance if the thickness , width > and length are known. > In practice its better to go for a lossier track and tap the voltage > across it with a potential divider, so target around 10 - 20 milli ohms, > cant use anything bigger as the board will get hot, 10A through 0.02 R > is 2 W, so better around 0.01 R > > Thanks > > -- > -- > Best wishes /73 > Richard Bown > Email : richard AT g8jvm DOT com > HTTP : http://www.g8jvm.com > nil carborundum a illegitemis > > ################################################################################## > Ham Call G8JVM . OS Linux Mint 16 x86_64 on a Dell Inspiron N5030 laptop > Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W > QRV VHF 6mtrs 200W, 4 mtrs 150W, 2mtrs 400W, 70cms 200W > Microwave 23 cms 140W, 13 cms 100W, 6 cms 0W & 3cms 5W > > ################################################################################## > > --047d7bfcfc62e0143604f719b24a Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">Why does it need to be TO-220? 3W wire shunt is about 50 c= ents. <br></div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quot= e">On Tue, Apr 15, 2014 at 2:54 PM, Richard Bown <span dir=3D"ltr"><<a h= ref=3D"mailto:richard AT g8jvm DOT com" target=3D"_blank">richard AT g8jvm DOT com</a>>= ;</span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex">Hi,<br> I thinking of playing with the LTC1645 using its for over current shut<br> down,<br> it requires only 50mV across a shunt resistor to trip, at 10A thats<br> 5milli ohm.<br> And those resistors in TO-220 packages are expensive, so I was thinking<br> why use a length of wide track, needs to wide as handling up to 10A .<br> Are there any tables to give track resistance if the thickness , width<br> and length are known.<br> In practice its better to go for a lossier track and tap the voltage<br> across it with a potential divider, so target around 10 - 20 milli ohms,<br= > cant use anything bigger as the board will get hot, 10A through 0.02 R<br> is 2 W, so better around 0.01 R<br> <br> Thanks<br> <span class=3D"HOEnZb"><font color=3D"#888888"><br> --<br> --<br> Best wishes /73<br> Richard Bown<br> Email : <a href=3D"mailto:richard AT g8jvm DOT com">richard AT g8jvm DOT com</a><br> HTTP =A0: =A0<a href=3D"http://www.g8jvm.com" target=3D"_blank">http://www.= g8jvm.com</a><br> nil carborundum a illegitemis<br> ###########################################################################= #######<br> Ham Call G8JVM . OS Linux Mint 16 x86_64 on a Dell Inspiron N5030 laptop<br= > Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W<br> QRV VHF 6mtrs 200W, 4 mtrs 150W, 2mtrs 400W, 70cms 200W<br> Microwave 23 cms 140W, 13 cms 100W, 6 cms 0W & 3cms 5W<br> ###########################################################################= #######<br> <br> </font></span></blockquote></div><br></div> --047d7bfcfc62e0143604f719b24a--
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