koolguy
Active Member
Or should i use transformer rectifier ?^^No problem with 9V SMPS. I actually like them and collect them. Want some?
Regards,
tvtech
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Or should i use transformer rectifier ?^^No problem with 9V SMPS. I actually like them and collect them. Want some?
Regards,
tvtech
It is not battery project it is professional market board.. with SMPS.
that 3.2V across collector resistance will diss power and become to hot!
Transfer resistor.... You need to design the BJT to your circuit... If you fully turn on the transistor then there should be nearly 7.2v across your resistor... BUT if you work out your current gain you can partially switch on the BJT to give a smaller voltage across your resistor so the BJT dissipates some of the power...
At the moment ALL of the power is lost in the resistor... Using the BJT share the power loss between them..
can you explain further more how to BJT has raised it voltage drop so high across it?Transfer resistor.... You need to design the BJT to your circuit...
i was testing with 9Vbattery and i have to used SMPS for long time.When did the game plan change???
He has a 20k pot!!Are you still using a BC337 PNP transistor? What is driving its base?
Its datasheet shows that some of them saturate poorly (VCE=0.7V) when the collector current is 500mA and the base current is 50mA.
If the base current is 50mA then part of the 20k pot will have 8V across it (VBE is about 1V) and with 50mA then its value is only 8V/50mA= 160 ohms.
Then the portion of the pot is only 160/20k= 0.8% which is nothing. The tiny part of the pot will smoke when it tries to dissipate 8V x 50mA= 0.4W.
I am going to drown myself in beer.
Basics, basics, basics.
You can't build anything without a solid foundation. Applies to houses and everything Electronic too..
More beer please Waiter.
Regards Waiter. See you Tomorrow.
tvtechI am going to drown myself in beer.
Basics, basics, basics.
You can't build anything without a solid foundation. Applies to houses and everything Electronic too..
More beer please Waiter.
Regards Waiter. See you Tomorrow.
tvtech
With a 20k base resistor at ground, the base current is (5V - 0.7V)/20k= 0.215mA. Then the maximum collector current can be 0.215mA x 20= 4.3mA, or maybe 0.215mA x 50= 10.75mA. Very low currents.
With the transistor turned off when its base resistor is +5V then you cannot use a 9V supply for the emitter.
5V is the maximum allowed reverse-bias emitter to base voltage for most transistors. Exceeding this voltage causes the emitter-base junction to breakdown like a zener diode which damages the transistor.The 5v is given by Data sheet maximum 5v can be used..
The pot is in series..... (I hope there is a 1k in there as well) So he shouldn't see 5v base to emitter... But then we are talking about Ritesh...5V is the maximum allowed reverse-bias emitter to base voltage for most transistors. Exceeding this voltage causes the emitter-base junction to breakdown like a zener diode which damages the transistor.
But the base to emitter is almost always forward-biased in most circuits and 5V is NEVER used.
sorry one other thing i wanted to say, it would never have occured to me to work out what % of the pot was being used. its seeing info like this and real working out that makes threads like this real gem's ok i admit the OP drives a few mad but beginners like me take notes of this stuff is real good learning stuff thanks guy'sIf the base current is 50mA then part of the 20k pot will have 8V across it (VBE is about 1V) and with 50mA then its value is only 8V/50mA= 160 ohms.
Then the portion of the pot is only 160/20k= 0.8% which is nothing. The tiny part of the pot will smoke when it tries to dissipate 8V x 50mA= 0.4W.
Hi Lgsorry for a hijack but can i ask a question please? why is 5v never used at the base? what about a pic pin?? or am i not understanding hmmmm i think i am missing the meaning of base to emiter rather than base?? sorry for the question
really sorry Ritesh for hijacking, is Q1 and Q2 in the Emitter follower configuration? just checking if i am learning any of this stuffDark beer or light beer? I think I only have light beer....... In small bottles...... No glasses.......
R,
Try this one.