Arduino Nano BC547B

Using Arduino General Electronics
1

Hallo,

ich würde gerne mit einem Transistor eine weiße LED-Leiste via PWM anstuern. (Also eigentlich 16x )
Die Schaltung an sich hat auch funktioniert, die Platine war fertig gelötet. (Recht viel Arbeit)

Allerdings hatte ich dann das Problem das der Arduino nach einigen Sekunden betrieb extrem warm wurde.
Ich habe bestimmt 2-3h die Platine durchsucht aber nirgends irgendeine Schwachstelle (Kurzschluss) gefunden.

Da das Problem immernoch da war wollte ich von neu Anfangen mit meinen Berechnungen und würde gerne bei der Berechnung des Basiswiederstands hilfe haben.

Also hier mal ein paar Infos.

Ich hoffe mir kann jemand helfen.

Falls die Frage aufkommt wieso ich diesen Transistor genommen habe:

  • Die Dame hintern tresen von Fachhandel hat mir den empfohlen. Habe ihr alles geschildert.

Vielen Dank
Sascha

PS: Falls jemand einen besseren Transistor hat, kann ich auch wechseln.

2

Problem # 1: BC547 -Collector Current − Continuous IC 100-200 mAdc MAX RATING! LED with 200mA will be a problem. You never want to use MAX parameter as what you USE. that is the point where the part starts to "break". Maybe a BD139 would have been better. What value Base resistor do you have between the arduino pin and the transistor?

Problem #2: You did not share your drawing.n Hard to give advice... but it sounds like your base current was to high... Which makes the AVR HOT

Sample Circuits:

760×332 31 KB

3

Thanks for fast reply quickly,

up to now I used a 1.8 Ohms 5% resistor (Brown, Grey, Gold, Gold) because once I got this value.

This is how it looks like:

Screenshot (18).png
Screenshot (18).png812×768 172 KB

Screenshot (19).png
Screenshot (19).png907×775 278 KB

4

huh ?

5

Hi

Where was the arduino hot?
What was your actually current?

Wo war dein Arduino heiss?
Was war der Strom welcher über deine Kontakte floss?

6

Where was it hot... I should have asked... now that I see the schematic... it is very likely that the voltage regulator got very warm.

7

pwillard:
Where was it hot... I should have asked... now that I see the schematic... it is very likely that the voltage regulator got very warm.

is there any possibility to fix this?

Gehtschon:
Hi

Where was the arduino hot?
What was your actually current?

Wo war dein Arduino heiss?
Was war der Strom welcher über deine Kontakte floss?

The think it was the Atmega which got very hot.
Well I don't know what my actually current was. (unfortunally)

8

Do the math.
Let Vf = 2.0V

5V-2V=3V

3V/180 ohmes = 16 mA

16 mA * 30 leds = 480 mA

Absolute Max rating for BC547 = 100 mA

Of course it's hot. You're running it at 5 times the rated current.

9

.. but it will get cold pretty soon, promised :slight_smile:

Go with a BD type or a MOSFET, which can carry the load.

10

Cold as in dead ?

11

Well I see the problem...
Which transistor/mosfet would you prefer?

It would be awesome if you could give a besser mosfet with the right resistor.

Best thanks. If my project is finished I will show you my result :slight_smile:

12

What is the problem then ?

13

Wow... you really did say 1.8 Ohms!!! So... well... this is how you make an AVR hot and die young.

Raschemmel was nice and gave the benefit of using 180 Ohms... Still wrong.. but closer. You should have had more like 500-1000 ohms.

And, like I said already... should have used bigger transistors from a current capacity perspective.

14

pwillard:
Wow... you really did say 1.8 Ohms!!! So... well... this is how you make an AVR hot and die young.

Yes i did :smiley:

wich Transistor would you use?

15

Yes i did

Ouch ! My finger hurts from touching the transistor !

16
  1. don't use 1.8 Ohms,replace with 1000 ohms
  2. Use the BD device I mentioned
17

raschemmel:
Ouch ! My finger hurts from touching the transistor !

Well mine was hurting too.

And I will try a BD139 the next days...
Thanks all

18

pwillard:

  1. don't use 1.8 Ohms,replace with 1000 ohms
  2. Use the BD device I mentioned

So i just got some BD139 today.
And now I should a 1kOhms Resitor, right?

19

start there... but lower value is likely required. read the datasheet

20

Well if I was able to understand the Datasheet I wouldn't need to ask.
Thats the problem.
And I have only a (very small) basic understanding of this.
I am more common with programming.

But I will try