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PIC18F46K20 PWM not working
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Ellest96



Joined: 15 Nov 2013
Posts: 17

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PostPosted: Sun Jan 25, 2015 2:54 pm     Reply with quote
temtronic wrote:
Yes BUT you MUST use a resistor to connect PIC to base of transistor !!
I'd suggest a 470r or 1K to start.
Typically you use an NPN transistor, with emitter connected to ground, 1K resistor from base to PIC I/O pin, collector to fan -ve lead, fan +ve lead to +5 volts.
This is all basic Electronics101 , tons of info on the web, be sure to get/read the datasheet for the NPN transistor you've chosen.

NOTE!!! I had a look at your schematic.
NOTE!!!! The 2N706 will NOT work for you!!! It is only rated for 50ma of collector current. Your fan needs 500 ma. You'll need to choose another transistor. It should be 'ok' for the backlight LED drive but NEEDS a base resistor(say 470r ).


hth
jay

ok, I will use a resistor for the transistor.
I've removed the PNP and put on a NPN, and on the schematic the transistor is wrong becouse there isn't the one that I have so I picked one random just for the symbol.

Now I'm using the BC546B and the BC337, which one is better for the fan (500mA) and which for the lcd backlight (220mA)?
Thank you Smile
temtronic



Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario

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PostPosted: Sun Jan 25, 2015 5:06 pm     Reply with quote
The BC337 is the better device to use. If you look at the first page it shows 'collector current - continuous' to be 800ma, whereas the BC546 is only 100ma.
You'll still need a base resistor, try 470r to begin with.

These days though 'logic level' FETS are the best choice.They're easier to interface to PICs, control more power, and usually cheaper than a 'regular' transistor.


jay
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