Electronics > Beginners
Picking a transistor.
(1/6) > >>
paulca:
I only have NE2222 and BC548's, but I have a project that needs more current than they can handle.

Basically switching a 12V line using a 3.3V PWM pin on an MCU.  It's driving some 5050 LEDs, 12V with groups of 3 in series.  Power is meant to be 14.4W/m, so call that 15W/m, I have 2 meters, so that's 30W or 10W per colour, so 10W / 12V ~= 1 Amp per transistor.

Would these do:
https://uk.rs-online.com/web/p/bjt-bipolar-transistors/7390347/

BTW, these are the LEDs with GND, RED, GREEN, BLUE connections, not the digital WS8212s
MagicSmoker:
That's a PNP BJT optimized for audio amplifiers, so probably not the correct polarity and otherwise not ideal.

Can you post the schematic you are working off of?

paulca:
Basically this.
https://randomnerdtutorials.com/10-diy-wifi-rgb-led-mood-light-with-esp8266-step-by-step/

But with 2 x 1 meter of strips of LEDs.

A thought did occur to me.  These are to light a fish tank that contains plants.  I could need it to power 4 strips.  60W, 20W per colour.
ledtester:
The typical solution for low side switching with a microcontroller is a logic-level N-channel MOSFET.

Get one that will fully turn on at 3.3 volts. Searching for "arduino 3.3v logic level mosfet " should bring up plenty of discussions and suggestions.
 
David Hess:
1 amp will require say 20 milliamps of drive current at a forced beta of 50 for a bipolar transistor which is marginal for most logic outputs.  That means either using some sort of driver to provide higher base current, a Darlington bipolar transistor, or a MOSFET.

So bipolar transistors could be used but the higher cost of a power MOSFET is probably worthwhile for simplicity.  Or a higher gain higher current bipolar like the KSD5041 could mange a forced beta of 100 for 10 milliamps of drive current.  For suitable bipolar transistors, look for higher current devices so that they maintain their gain at higher currents.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod