Posted by derek [68.122.15.246] on Saturday, June 29, 2013 at 15:56:15 :
In Reply to: Re: Correct posted by TGP (IL) [205.188.116.5] on Saturday, June 29, 2013 at 13:44:50 :
V=IR P=IV
You know the voltage drop you want. the hard part is determining the current draw from your gauge. With the voltage and current you can easily figure the resistance you need. Next plug your known values back into the power equation to find out what power rating the resistor needs to be. A commonly available (and cheapest) 1/4 or 1 watt versions will likely yield their smoke to the atmosphere all too easily (instantly). You'll need a powerful resistor that plays hard to get and gets really hot instead of burning up.
Avoid banging electrons together to make heat and instead get them to do some useful work for you. Go with a solid state semiconductor "runtz" style product mentioned elsewhere on this forum #422. There are likely other brands, models and vendors if the runtz doesn't suit your needs. Or follow the links and learn how to roll your own.
High power resistor example, image above:
http://www.newegg.com/Product/Product.aspx?Item=9SIA15Y0CM9855&nm_mc=KNC-GoogleMKP&cm_mmc=KNC-GoogleMKP-_-pla-_-Car+Electronics+Accessories-_-9SIA15Y0CM9855
Follow Ups: