Pages: [1]   Go Down
Author Topic: Using a transistor as a switch  (Read 365 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 13
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hello forum!

I want to switch the main power supply to a gps reciever(UP501) on and off. The gps reciever uses 1 pin for ground, 1 pin for back up power supply and 1 pin for main power supply. Using plain digital pins doesn't work, because the gps draws about 30mA on 3,3V. The back up power supply pin is always connected to 3,3V.
To make it work I want to use a transistor to switch the main power supply on and off. But my lack of knowledge about transistor isnt helping much. Can anybody help me with this?
Im using an arduino clone based on the arduino pro (3,3V;8MHz) w/ Atmega328.

Regards,

Leo
Logged

Valencia, Spain
Online Online
Faraday Member
**
Karma: 118
Posts: 4545
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You'll need a MOSFET for this. Almost any logic level N-Channel MOSFET will do.
Logged

No, I don't answer questions sent in private messages...

0
Offline Offline
Shannon Member
****
Karma: 160
Posts: 10418
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

No, this won't work, a p-channel MOSFET or PNP switching transistor to do high-side switching is required.  An n-channel
or NPN device can only do low-side switching on the ground which is incompatible with maintaining the backup 3.3V
supply.  Search for high-side switching, p-channel and/or PNP.
Logged

[ I won't respond to messages, use the forum please ]

Montreal
Offline Offline
Edison Member
*
Karma: 23
Posts: 2485
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Probably, you may "simplify" this circuit, leaving T1 only, than driving LOW to turn on device
http://ruggedcircuits.com/html/circuit_-17.html
Logged

0
Offline Offline
Shannon Member
****
Karma: 160
Posts: 10418
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Indeed - losing Q1 would improve that circuit!
Logged

[ I won't respond to messages, use the forum please ]

Offline Offline
Edison Member
*
Karma: 20
Posts: 2104
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I dunno, I think a 2n2222 might be up for the job....
Logged

Pages: [1]   Go Up
Jump to: