Multiple LED's on one pin?

Started by smitty505000 November 9, 2003
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



--- 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



> 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


--- 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




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





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





> 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



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





I too can vouch for www.glitchbuster.com as I've been very happy with my purchases there.
-----Original Message-----
From: Phil [mailto:p...@yahoo.com]
Sent: Sunday, November 09, 2003 11:57 AM
To: p...@yahoogroups.com
Subject: [piclist] Re: Multiple LED's on one pin?

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 p...@yahoogroups.com, "smitty505000" <smitty505000@y...>
wrote:
> --- In p...@yahoogroups.com, "Dave Mucha" <davemucha@j...> wrote:
> > --- In p...@yahoogroups.com, "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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> 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