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Hey guys, Do I need a transistor to drive say 10 LED's on one output pin? Its going to be like 220ma. If so what kind of transistor? Thanks, Smitty |
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Multiple LED's on one pin?
Started by ●November 8, 2003
Reply by ●November 9, 20032003-11-09
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--- In , "smitty505000" <smitty505000@y...> wrote: > Hey guys, > > Do I need a transistor to drive say 10 LED's on one output pin? > Its going to be like 220ma. If so what kind of transistor? > > Thanks, > Smitty pn2222 1 amp TO-92 case digi-key PN2222-ND 30 cents |
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Reply by ●November 9, 20032003-11-09
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> Do I need a transistor to drive say 10 LED's on one output pin?
not if you use 2mA LEDs. you might even succeed in putting two in series, so the total current could be 10 mA. > Its going to be like 220ma. If so what kind of transistor? I would go for a big one to have room for experimental errors, so a TIP120. Wouter van Ooijen -- ------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products |
Reply by ●November 9, 20032003-11-09
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--- In , "Dave Mucha" <davemucha@j...> wrote: > --- In , "smitty505000" <smitty505000@y...> > wrote: > > Hey guys, > > > > Do I need a transistor to drive say 10 LED's on one output pin? > > Its going to be like 220ma. If so what kind of transistor? > > > > Thanks, > > Smitty > pn2222 > > 1 amp > > TO-92 case > > digi-key PN2222-ND 30 cents Thanks so much! I can get them from my favorite place "www.jameco.com" for 5 cents...lol Do I just hook it up with the base on the pic pin and the collector to +5 and emitter to the led? Thanks for the help, Smitty |
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Reply by ●November 9, 20032003-11-09
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Think about putting 2 LEDs in series and 5 parallel strings. So, the dropping resistor for each string is probably 5V - 0.2V (transistor) - 2.4V (1.2Vf per LED) / 0.02A or 120 Ohms. So, you need 5 strings each consisting of 2 LEDs in series with a 120 Ohm resistor. Connect the resistor to +5 then through the LEDs and on to the collector of the transistor. Connect the emitter to ground. Now, since the collector current will be 5 * 0.02A or 0.1A and the transistor gain is probably about 100 you only need 0.1 / 100 base current of 100 uA. Assuming the port can pull to +4V and the base- emitter drop is 0.6V we have 3.4V and 0.0001A or 34K for the base resistor. Choose, say, 10k. So, connect a 10K resistor from the I/O pin to the base. Check to see that the transistor is fully saturated (0.2V give or take from collector to emitter) and reduce the base resistor if necessary. If the port can drive 0.01A then the lower limit of the base resistor is +5V - 0.6V (base emitter drop) / 0.01A or 440 Ohms. --- In , "smitty505000" <smitty505000@y...> wrote: > --- In , "Dave Mucha" <davemucha@j...> wrote: > > --- In , "smitty505000" <smitty505000@y...> > > wrote: > > > Hey guys, > > > > > > Do I need a transistor to drive say 10 LED's on one output > pin? > > > Its going to be like 220ma. If so what kind of transistor? > > > > > > Thanks, > > > Smitty > > > > > > pn2222 > > > > 1 amp > > > > TO-92 case > > > > digi-key PN2222-ND 30 cents > > Thanks so much! I can get them from my favorite > place "www.jameco.com" for 5 cents...lol > Do I just hook it up with the base on the pic pin and the collector > to +5 and emitter to the led? > > Thanks for the help, > Smitty |
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Reply by ●November 9, 20032003-11-09
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another good source of 2n2222s and TIP120s is www.glitchbuster.com. He's a small guy but honest as the day is long, very prompt and has great prices. the 2n2222's are 12/.98, TIP120s for .39 but more importantly, his PICs are well below the big guys. no minimums and he ships for a flat 1.85 first class (usa, only). Downside? he doesn't have a fancy ordering system and you pay via paypal. I always try to buy from him first. He's always asking for ideas on what to stock. I have no affiliation other than I use him and want to see him remain in biz... Phil --- In , "smitty505000" <smitty505000@y...> wrote: > --- In , "Dave Mucha" <davemucha@j...> wrote: > > --- In , "smitty505000" <smitty505000@y...> > > wrote: > > > Hey guys, > > > > > > Do I need a transistor to drive say 10 LED's on one output > pin? > > > Its going to be like 220ma. If so what kind of transistor? > > > > > > Thanks, > > > Smitty > > > > > > pn2222 > > > > 1 amp > > > > TO-92 case > > > > digi-key PN2222-ND 30 cents > > Thanks so much! I can get them from my favorite > place "www.jameco.com" for 5 cents...lol > Do I just hook it up with the base on the pic pin and the collector > to +5 and emitter to the led? > > Thanks for the help, > Smitty |
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Reply by ●November 9, 20032003-11-09
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> another good source of 2n2222s and TIP120s is www.glitchbuster.com. Looks a bit like my shop. I'll look closely at his list to see what i should stock too :) Wouter van Ooijen -- ------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products |
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Reply by ●November 9, 20032003-11-09
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what do you charge to ship to seattle?? :( Phil --- In , "Wouter van Ooijen" <wouter@v...> wrote: > > another good source of 2n2222s and TIP120s is www.glitchbuster.com. > > Looks a bit like my shop. I'll look closely at his list to see what i > should stock too :) > > Wouter van Ooijen > > -- ------- > Van Ooijen Technische Informatica: www.voti.nl > consultancy, development, PICmicro products |
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Reply by ●November 9, 20032003-11-09
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I too can vouch for www.glitchbuster.com as I've been very happy
with my purchases there.
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Reply by ●November 9, 20032003-11-09
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> what do you charge to ship to seattle?? :( I am in the Netherlands, so my (fixed) shipping/handling cost increases from E 3.00 (Netherlands, incl VAT) to E 5.00 (Europe, incl VAT), to US$ 7.35 (World, excl. VAT). So having a shop like mine or glitchbuster's in every country will make the hobby more affordable. BTW for some reason that I don't understand my business one year ago was 1/3 Netherlands, 1/3 Europe, 1/3 rest of the world. Now it is more like 9/10 Netherlands. I do have a web interface for my shop, but I wrote it all myself. Some say that shows. Wouter van Ooijen -- ------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products |
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