Ok, It has been a long time since I was in Electrical Engineering 101. But, I believe this is a case where Ohms law needs to be applied to figure out the correct type of pot to use. In fact, I think you actually want to use a rheostat.
Ohms law states that V = I X R or voltage equals I (amperage) times R (resistance) . Since you know your voltage is 12 VDC and you are trying to calculate the needed resistance then you can calculate Ohms law the following way. R = V / I If your calculations show that you are trying to dissipate much more then 1 watt, then as I recall you are going to have heat build up. So you may need to consider the value of R and have a heat sink. Remember, the more heat the greater the chance the pot or rheostat with heat up and eventually fail. The below item that Jose is recommending is for LED use which is different then calculating a pot for incandescent bulbs. I do not believe you could safely use a device designed for LED control on an incandescent bulb. But, it has been more years than I want to admit since I was an engineering student but, I am pretty sure I am right. An incandescent bulbs brightness is controlled by limiting the amperage to the bulb. A LED's brightness is controlled by the voltage to it. So as I recall for an LED you would want a variable power supply type of device with a voltage regulator at its core. By design it would be solid state and not be as big a heat source as say a pot or Rheostat. The ebay device in which Jose is pointing to is for LED use. Yes, the ad states at the bottom that it can be used for incandescent bulbs. I am not sure how well it would work because it is a voltage limiting device. My two cents worth and I qualified its been a while. Jeff York Georgetown Scott County airport 2010 KR Nationals Peoples Choice and best interior 2011 Air Fest Best Experimental and Best Instrument panel ________________________________ From: Jose Fuentes <jose.fuen...@gmail.com> To: KRnet <kr...@mylist.net> Sent: Tuesday, October 18, 2011 10:31 AM Subject: Re: KR> POT OHM OR K? Thanks, that's a great IDEA I will move to that one, just purchased it, much perfer a solid state version. Joe On Tue, Oct 18, 2011 at 9:54 AM, Jeff Scott <jscott.pla...@gmx.com> wrote: > I would suggest not using the old heat dissapating resistive dimmers and go > to a solid state LED dimmer. > < > http://www.ebay.com/itm/LED-Dimmer-12-volt-panel-dash-mount-on-off-12V-DC-/320764532724?pt=LH_DefaultDomain_0&hash=item4aaf0e57f4 > > > This is a switching controller, so works very well with LED or incandecent > lighting. This particular unit is $15 and very compact. It maxes out at 1 > amp. There are others on Ebay that carry up to 8 amps. I used this for the > internal lighting in my SuperCub and have another one I'll be mounting in > the KR soon. > > Jeff Scott > Los Alamos, NM > > ----- Original Message ----- > > On 2:59 PM, Jose Fuentes wrote: > Hi everyone, > > does anyone recommend a > good POT OHM/K value for use as a dimmer? > Joe > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > -- Jose Fuentes Founding Father (one of and former Vice Prez) of Capital City.NET User's Group Former Microsoft MVP http://blogs.aspadvice.com/jfuentes _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
