hugoender
New Member
I have a Parallax passive infrared motion sensor (**broken link removed**) and am trying to have it activate a wireless transmitter (the type that is found in one of those cheap wireless door bells).
Since the motion sensor only outputs 3.3V and around 2.2mA (from what I measured), I added a transistor (2N2222) to act as a switch.
I first experimented with the transistor by itself by connecting Vc and Vb to wall-wart supplies. The base I connected to a voltage divider (R1=12Ohms, R2=22Ohms) with an input of what is supposed to be a 5V 550mA wall-wart to give me 3.3V at Vb. I have 3.3kOhms between Vcc and Vc and Vcc is a 15V, 400mA wall-wart.
The wireless transmitter normally uses a 12V MN21 or A23 battery but I have it's + and - terminals connected to the 3.3kOhms and Vc respectively.
With this setup, everything works fine. However, my issue arises when I switch the 5V wall-wart and voltage divider with a battery pack (3 AAA) to give me 4.5-5V. I connect this pack straight to Vb with no resistor. I don't know why this does not work. I don't think it takes much to saturate the transistor.
Any help would be greatly appreciated. Thank you.
Since the motion sensor only outputs 3.3V and around 2.2mA (from what I measured), I added a transistor (2N2222) to act as a switch.
I first experimented with the transistor by itself by connecting Vc and Vb to wall-wart supplies. The base I connected to a voltage divider (R1=12Ohms, R2=22Ohms) with an input of what is supposed to be a 5V 550mA wall-wart to give me 3.3V at Vb. I have 3.3kOhms between Vcc and Vc and Vcc is a 15V, 400mA wall-wart.
The wireless transmitter normally uses a 12V MN21 or A23 battery but I have it's + and - terminals connected to the 3.3kOhms and Vc respectively.
With this setup, everything works fine. However, my issue arises when I switch the 5V wall-wart and voltage divider with a battery pack (3 AAA) to give me 4.5-5V. I connect this pack straight to Vb with no resistor. I don't know why this does not work. I don't think it takes much to saturate the transistor.
Any help would be greatly appreciated. Thank you.