Just some questions

[Devilz Rej3ct]

I was wondering if anyone can tell me where to get a micro or mini potentiometer? Preferably one with a value of 100 ohms. Also I have a laptop which is dead now, but it has a DVD burner in it. Would the diode be any use in it? It is a HP Pavilion DV6000. Thanks.

 

[Devilz Rej3ct]

11 views and no one knows?

 

[HIMNL9]

Uhm, do you mean trimmers ?

Ebay, sometimes ..... or RS components (more high prices)

Something similar to this, i suppose ?

12 Copal ST5 100 Ohm 14 Turn Prec. Trim Potentiometers - eBay (item 200366467360 end time Jan-20-10 07:18:32 PST)

60 Beckman 200 Ohm Single Turn 1/4" PCB Trim Pots - eBay (item 7513915221 end time Jan-09-10 13:03:34 PST)

198 PANASONIC 220 OHM 3MM SEALED SMT 3 TT TRIMMER POTS - eBay (item 200399823754 end time Jan-27-10 06:49:12 PST)

 

[Deleted member 8382]

If the DVD burner is a DVD-RW writter it might be profitable, about the pots, get to any electronic parts supplier, if you're in USA I think Radioshack sells them.

 

[Greenmechanic]

The lowest Radioshack sells is 1k. At least in my area.
The 15 turn ones (271-0342) will work, but they are touchy in the higher ranges. (250-750mA)

 

[silvercookie]

mouser and digi-key would definitly have what you are looking for.

 

[Deleted member 8382]

anyway, are you willing to use the driver to build the DDL driver? If so, I recommend you to don't use the pot, just place the resistors that you need for your diode and forget about regulating it later!

 

[HIMNL9]

The 15 turn ones (271-0342) will work, but they are touchy in the higher ranges. (250-750mA)

Cause the basical scheme that anyone use, have a conceptual error from the start ..... all the current is passed through the trimmer, and if isn't an 1W trimmer, it fry, and also, the current increase exponentially in the last millimeters of the cursor path .....

Try to use my version, instead (changing the values for match your needs), and you will see that you can regulate it better, and fry less trimmers (also with 100 ohm trimmers )

http://laserpointerforums.com/f51/help-please-45563.html#post614285

But i agree also that set it fixed is the better way, for a module driver ..... only for unknown regulations, or for lab drivers, a current regulation have sense, imho

 

[Deleted member 8382]

Why so many capacitors? Have you tried it on an oscilloscope? I test an lm317 at 150mA without any capacitor and the output was very very clean, add it a single 47ufd at the output side and you almost have a neat line!

 

[HIMNL9]

Why so many capacitors? .....

Cause, sometimes, linear regulators tend to self-oscillate, and if this happens, they stop to regulate ..... is not a common thing, and usually it don't happens, but i had some 1117 that was stable with 470nF, and some others that needed 10uF in parallel to the ceramic capacitors, otherwise they don't regulate the current (goes in self-oscillation) ..... same schematics, same PCB, sometimes it happens and sometimes not .....

Manufacturers, anyway, always suggest to use at least 100nF at the input, and at least 330nF at the output, for avoid this thing .....

 

[Deleted member 8382]

oh I see. Thanks