2n3055 for PWM driver for RGB leds

Thread Starter

Hedalen

Joined Dec 5, 2010
19
hi, i am new here and like to ask you something about the 2N3055

de datasheet tells me:
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
NPN 2N3055
PNP MJ2955
VCBO Collector-Base Voltage (IE = 0) 100 V
VCER Collector-Emitter Voltage (RBE £ 100W) 70 V
VCEO Collector-Emitter Voltage (IB = 0) 60 V
VEBO Emitter-Base Voltage (IC = 0) 7 V
IC Collector Current 15 A
IB Base Current 7 A
Ptot Total Dissipation at Tc £ 25 oC 115 W
Tstg Storage Temperature -65 to 200 oC
Tj Max. Operating Junction Temperature 200 oC
For PNP types voltage and current values are negative.


but can i use it with 5V level and steering the basis with 5 volt from a pic chip
 
Last edited by a moderator:

bertus

Joined Apr 5, 2008
20,230
Hello,

A 2N3055 is a current controlled transistor.
For full saturation you will need a base current of about 0.1 X collector current.
As the pic can only supply about 25 mA , you will not have more than 250 mA at saturation.

What do you want to control with your pic?

Bertus
 

Adjuster

Joined Dec 26, 2010
2,148
Of course, you could add a smaller transistor between the pic and the 2N3055 to provide more base drive, but perhaps a logic-level MOSFET would be neater than using two bipolars like that - and it would drain less current from your supply.
 

Thread Starter

Hedalen

Joined Dec 5, 2010
19
hi, thanks for your quick reactions.
I have a project here @ home, for making many many leds in the floor
so that we can see by a power break where we can walk.
i am talking about nearly a 120 leds ( blue ) and about a 45 rgb leds
from the rgb leds will change the colors but everytime the red, green or the blue color will light on the same time, so that will be 3 ports on the chip
the blue leds are sometimes ( max 3 )parallel, sometimes just 1.

so all power will come out a accu (12V) when the power goes down
 

SgtWookie

Joined Jul 17, 2007
22,210
Hello Hedalen,
If you are using a 12v supply (12v lead-acid battery, maybe?) you might use up to three of the blue LEDs in series with a current limiting resistor. If each blue LED needs 20mA current, then 120 LEDs / 3 * 20mA = 800mA total current required.

The RGB LEDs cannot be operated in series, so you will need a current limiting resistor for each R, G, B leg for each display. The resistor for red LED will be a different value than for the green or the blue.

Like Adjuster said, you should consider using logic-level MOSFETs.
 

Thread Starter

Hedalen

Joined Dec 5, 2010
19
sorry, but the leds are (max 3) parallel
they have them own 1K resistor and the RGB's are common anode (+)
and so each RGB has 3 resistors.
@ one place in the house comes all the cables ( UTP cat6) together, for mounting on a print with the transistors and the chip(s)
 

Thread Starter

Hedalen

Joined Dec 5, 2010
19
ones i wil try to work with pic chips and PWM special for RGB-leds, but i think that is difficult for me, be course it is a new world for me
The big problem will be the time, when 1 color = 0 , 1 = 50 and 1 = 100 percent
 
Last edited:

Thread Starter

Hedalen

Joined Dec 5, 2010
19
i keeps the problem
to change from the first color at ≈ 83% to start the next color and at least the third color when the first color is at ≈ 166%
 

bertus

Joined Apr 5, 2008
20,230
Hello,

What is the circuit you are using?
Can you post the circuit diagram?

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PS I have moved the thread to the embedded forum.
 

Thread Starter

Hedalen

Joined Dec 5, 2010
19
@ Bertus,

at this moment is it not a problem that i will loose 2x 0,7V, because i use 1k resistors so i can use a external power supply up to ≈20V.

@ nickelflipper,

i will try to find out what i can use for proton IDE
 

Wendy

Joined Mar 24, 2008
21,929
If you go to my link on Chapter 10, Transistor Drivers, you will find MOSFETs are much more suited to this application. That particular chapter will describe in detail how to go about it. PICs are a subset of the much larger field of electronics.
 

Thread Starter

Hedalen

Joined Dec 5, 2010
19
okay, listen

i live in Norway, and it is very expensive to buy here components( 1,50 euro for 1 resistance)
and i have to drive about a 90 km 1 way.

is there a possibility to do something with just some pic chips, some bc547b and some 2n3055???
 
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