NPN switch, needs advice on potential current loss.

[patr0805]

Hi electro noob here!
I am making a small project where I need an electromagnet turned on and off many times a second. As such I cannot use a relay to have the Arduino switch an external powersource to the electromagnet. I have been trying to make the following circuit as seen in this link:
https://sebastianpatten.files.wordpress ... tities.jpg

I am using a MMBT2222A NPN Bipolar Transistor, 1 A 40 V, 3-Pin SOT-23 transistor, but when I switch on the transistor the electromagnet becomes very weak compared to directly plugging it to the external powersource (External powersource is rated at 9V 1300mA). Now why is this happening? Shouldn't I be able to omit using a relay by using a transistor given the right readings? (I chose the MMBT2222A because the 1A rating was the closest I could find to the 1300mA external power supply).

Also is there some other tips you could give on this kind of application?
Thanks for the help

[KMoffett]

The maximum output current rating of the external supply is not the issue. What is the current drawn by the electromagnet at 9vDC? The transistor's base current should be about 1/10 (rule of thumb) of the magnet current. If the controller's output is ~5V, than you are only driving the base with about 4mA.

Ken

[patr0805]

I will buy myself a voltmeter tomorow and will tell you the measurings then. To give a little more info on my setup, my electromagnet is a 1,5cm long, 1,5mm diameter nail that has about 300-400 turns. The transistor base is connected to an Arduino logical pin with an 1KOhm resister in between. Emitter goes to GND and collector to Load which goes to the 12V external powersource.