Controlling a transistor with an Arduino

Using Arduino General Electronics
1

Hi
I want to do a small project with an Arduino and a transistor to control a 12V PC fan using a 12V 1.5A power supply.
But as you know nothing works in the first try.
The circuit worked fine and i connected a 12V led and it turned on.
But when i connected the fan it turned on but not at full speed and when i measured the voltage it dropped and the current was limited to 40 MILLIAMPS.
After trying again and again it didn't work
The transistor i used is an E13007-1
Any help would be appreciated
The circuit screenshot link is attached

Edit: it turns out that the 1k base resistor wasn't the right one and now i connected two 220ohm resistors in parallel and now the current reaches 1A
Thanks for all your help.

Screenshot_17~2.png
Screenshot_17~2.png651×661 167 KB

2

Do a real schematic, these fuzzy drawings are next to useless. That 1K base resistor is not near enough drive for that transistor. your 40 miliamps is about correct, your fan is in current limit mode. Try something in the 250 Ohm range. You might consider getting some Avalanche Rated logic level N-Channel MOSFETs, then you do not have to worry about resistors or diodes and if done properly no heat sinks.

3

what is a current limit mode
So if i used a 220 ohm resistor will it work?

4

The MJE13007 is not a darlington, so you'll need to give its base 10% of the load current to switch on fully.

Change the base resistor to 150 ohms or so.

5

Thanks will try that tomorrow

6

With the fan being an inductive load you need a fly back diode across (parallel) the fan connection with the cathode at the positive and anode at the negative. This might be why your transistor no longer works.

7

It still works but it doesn't supply more than 40 mA and no the fan does not make any voltage spikes (i don't know what is the right name) so i don't worry about it.

8

Rather than edit the original posting to say it now works, put that comment at the end, a thread is a story, the end belongs at the end, otherwise its completely confusing for someone reading it afresh. You can tag the thread as [solved] if you want.

and now i connected two 220ohm resistors in parallel and now the current reaches 1A

That may be pushing things, the collector current is 30 times the base current, so the transistor won't be fully saturating and may get hot - some heatsinking would be good. A MOSFET is much better for
higher currents as the dissipation can be made very small by picking one with a low-enough on-resistance.

9

You're not trying to source 40mA from an Arduino output pin, are you? You need a MOSFET like FQP30N06L or similar.
https://www.onsemi.com/products/discretes-drivers/mosfets/fqp30n06l

10

Hi

PLEASE can you post a copy of your circuit a picture of a hand drawn circuit in jpg, png?

Not a Fritzy, reverse engineer your project to draw your circuit.

Tom.. :slight_smile: