So which transistor to use??

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Slickit

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Hello again every one you may remember from such threads as "PCB made to my schematic?" and other great posts but i am here today for a more simple problem, and that is which transistor do i use in my growing schematic design. It not my original schematic but i am attempting to change it to my desires. The schematic below is the original but what i want to do with it is slightly different. Ok here we go, imagine a star consisting of about 150 LEDs (nte30041) the star will be broken into 5 sections, each section is a "leg" of the star and those sections will have 30 LEDs in them. The sections are 10 rows high and from 1-5 leds wide, i am working on a picture now. And the problem i have is supplying the current for all of these leds. Now i can either run each section off of its own LM3914 or use one to trigger all sections but what i want to do is have a separate voltage source or more particularly a separate current source. And i want to use transistors off the output of the LM3914 to trigger the other source. So the question is what transistor do i use, it will have to be a PNP but im not entirely sure about that, i say that cause this circuit is synced instead of sourced.

Circuit origionally created by gary
 

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Since you are using 12V for the circuit you can put more than one LED in series on each output lead.
I have built circuits using the LM3914 and put opto coupler inputs in series with the output LED to drive other circuits. If you don't want to use opto couplers you may want to consider using some PNP darlington transistors. The emitter connected to +12V, the collector to the strings of LED's and a 1K resistor to the output pin of the LM3914. When the output goes low the transistor will turn on and the LED's will light.
A choice could be a TIP105
 
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PN2907A is a nice PNP, not a darlington but I don;t think it needs to be in this circuit. It's 9 cents at Goldmine (7 cents quantity 10 or more) SKU A20158. Lots of good deals on this part on eBay, best one is probably $4.48 for 50 pcs PN2907 from Kansas City including shipping.

Show us your schemaic first so we are on the same page.
 
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