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Author Topic: PNP transistors... how to use them?  (Read 3292 times)
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West palm beach, FL
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motors is 9-18v thats about all its said in the little radioshack bag. transistor is TIP42G
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West palm beach, FL
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the magic smoke reminds me of that show Lost.
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Leighton Buzzard, UK
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did you do anything about
a)
b)
c)
or
d)
??
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West palm beach, FL
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LOL i do have all those in place sir , i posted that for times sake i just did not draw them in , but the smoke is at bay! and connecting the resistor to 12v in fact shuts it off
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Leighton Buzzard, UK
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in that case it's working
now all you need to do is get the PMW signal up and running and Bob can marry your mother's sister

(hey and less of this sir stuff!)

cheers
Mike
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West palm beach, FL
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haha thanks for the insight!

like you said , Cheers!

(i didnt get the Bob reference) 
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Leighton Buzzard, UK
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you heard the expression "Bob's your uncle"?
means it's ok!
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West palm beach, FL
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never heard that in my 24  years hahaha but now i understand why he would marry my mothers sister.
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Manchester (England England)
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Quote
the emitter of the PNP and the collector to positive 12v and the base to an arduino pwm pin
You can't do that because the only way to turn the transistor off is to put 12V on the base, the arduino can only supply 5V so there is no way to turn the transistor off. Hence it is on all the time.
You need an NPN transistor to generate a 0 to 12V signal to use to turn the PNP on and off.
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Leighton Buzzard, UK
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fair cop
I was assuming (silly me) that the motor was running from 5 volts as well!)
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Leighton Buzzard, UK
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something like this?...

but you'd use 12v (can't find a suitable Fritz symbol smiley-sad )

my transistors go E B C for both
yours are different


* PNP.jpg (743.61 KB, 540x470 - viewed 24 times.)
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Manchester (England England)
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No like this:-
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Leighton Buzzard, UK
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I guess R2 is to ensure T2 really does get turned off?
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Well yes R2 is the thing that keep the transistor off in the absence of an on signal. In the old days there was always a pull down resistor like this on NPN transistors as well. This was because with germanium transistors the base threshold was only 0.25V and this could be triggered by pickup.
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Dallas, Texas
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you heard the expression "Bob's your uncle"?
means it's ok!

I had never heard that before either. Turns out, unless you live in or under rule of Britain, its not likely to have been heard.

This is a well timed thread as I was just started to read up on transistors.

Thanks.
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