ModelRailroadForums.com is a free Model Railroad Discussion Forum and photo gallery. We cover all scales and sizes of model railroads. Online since 2002, it's one of the oldest and largest model railroad forums on the web. Whether you're a master model railroader or just getting started, you'll find something of interest here.
I am looking for 1K ohm 1/2 Watt surface mount resistors. The only place where I've found them is Digikey. They charge a mandatory $7 reeling fee (which is a packaging fee since the components come on a reel) so I was wondering if anyone knew of any other places that sell them.
I checked NGineering, they don't have the 1K ohm surface mount resistor that is rated for 1/2 a watt.
But, using NGineering's calculator, it says .158 Watts.
I'm confused.
The values used are:
Supply Voltage - 16 Volts (thats what a few of the club's boosters are set at)
LED Voltage - 3.4 Volts
Current - 15 milliamps MAX (this is a surface mount LED)
Resistor - 1K ohm
Check eBay...I know, I know...but, I have had some luck finding parts at low prices, even some with free shipping from overseas. Electronic parts are so light that they can often just be put into a regular envelope and sent for very little money.
I picked up 200 resistors for $2.00, shipping was free. These were through hole components, but I'm sure someone will have SMD resistors.
For a resistor actually dissipating .15W, I'd have gone with the 1/2 watt models myself. BTW, dropping 13 volts at 15MA sounds like 0.195 watts to me. That's too close to the maximum dissipation of a 1/4W resistor to keep me feeling comfortable.
Unfortunately, I couldn't find any that didn't cost an arm and a leg (the half watt ones were not on ebay).
There are only 2 blocks or so on the club layout that puts out 16 volts (DCC) and I don't think the loco will sit in those blocks for very long so I'll test the connections before putting the loco back together, and see how hot the resistors get on those blocks.
You do know that you can use two 2K 1/4W resistors and stack them to get 1/2W, right? I've done this on several boards when I couldn't get the right wattage or value for a repair.
well, it's too late now, I already ordered the resistors. I do know that I can do that but I don't know if I will have enough room (hence the surface mount version)
