Can someone tell me where I can get a resistor like the one shown in the pic down in the middle?
I want to replace it with an R100 (0.1Ohm or 100mOhm if I'm correct).
I found quite a lot, its an SMD, but they exist in many different shapes.
RS Components will have one. (they have Minimum Order Quantities, so you will probably have to buy 10)
You need to measure the size of the resistor, to make sure you get the right one.
then you can search RS for the right size.
There is a list of sizes here (look for two-terminal packages):
Good Luck
Pete
Hey,
thank you, I even found one that might fit.. but after some measurements I decided to bridge the capacitor. Now pulling 2.2A from 2 AA eneloops.. so no more than 1.8A to the emitter. As the device will be QTC controlled -> no problem.
But thanks for the hint with RS components, great site!
Resistance is futile
Assuming that's a SOT23-6 there in the middle, that looks like a 1206 size to me. If it's an SC80 in the middle though, then it's more likely an 0805. We're talking about parts that cost a penny or two though, so get both if you're not sure. Bourns, Vishay/Dale, Susumu, KOA, Yageo, Panasonic - all good chip resistor brands.
Here, for example, is a quality R100 (100mOhm) 0805 part:
http://de.mouser.com/ProductDetail/Bourns/CRL0805-JW-R100ELF/?qs=OcJ73dDx4S1BYPUlNdh2oWXjOkXzWEDj
I would pick up a similar part in 1206 as well.
Mouser, Digikey, Farnell, Future - there are tons of suppliers of chip resistors.
The sizes I'm mentioning are in english units - 1206 = .120 " x .060" 0805 = .080" x .050"
PPtk
Resistor? I barely knew her! :bigsmile:
Rectum??
damn near killed him :)
Liquor wrecked 'em
LOL
Keith (who could not resist)
Resist her? I'll try, but I think she has the new flashlights I ordered! :p
Seriously, EBay has all that kind of stuff. I just bought 250 SMD resistors for 4 bucks plus shipping. Of course it's about 247 more than I really needed, lol, but that was still the best deal.
Dang! If she was my delivery person, I would be buying something every other day. 
100 milli ohms is a very small resistance, If it is to mod the driver for slightly more amps, why not install a small momentary contact switch using very fine wire to shunt the resistor. I am too busy (lazy) to try this, but I bet the wire to and from the switch would (could) be 0.1 ohm. You would end up, in effect, a Turbo mode. Has anybody tried this?
My suspicion is that all of the current for the emitter flows through the resistor. Very fine wire is not a good plan. In fact, if you want a 'turbo/DD' mode, you want FAT wire and a good switch to yield near zero ohm.
PPtk
I suspect that it is a "sensing" resistor. Putting all of the emitter current through it would mean that it would need to be about a 1 watt resistor. and it would also make the driver very inefficient. At 3 Amps (P=I*I*R) 3*3*0.1=0.9 watts. That resistor is probably an 1/10 watt or even smaller.
If it’s surface mount it’s definitely that small or less, 1 Watt resistors are pretty damn big relatively.
A current "sensing" resistor is a shunt resistor, and yes, all of the current flows through it, and no, it's probably not a 1/10th watt. Assuming it's a 1206 like I suspect, it could easily be a half watt, and they're available in even higher power capacities.
If it's a half watt 1206, then it could handle as much as 1.82 Amps flowing through it before being out of spec.
PPtk
Not really, 1206s can be had in 1 watt varieties (although somewhat rare) and 2010s are very commonly 1 watt or higher.
PPtk