[moved] Mospec transistor and bc547 npn transistor

[The-one]

Hello every one ,
can anyone post the tutorial of the mospec and how to connect it and use it as a switch ?

Is it possible to use it as a switch and give same power (example 9v dc and get 7or 8 v dc from it ) and collect same or lower voltage to triger a relay ?

I try to use npn transistor series n but with some how i can only get LED work but when i try to triger the 5v relay it does not work ,

i check the voltage and im geting 8,5v,

i dont much knowledge how to check the emps ,so whats the solution about this ,the circuit is should do light switch trigger but some how its not working for me ,
any help pls ?

 

[KlausST]

Hi,

Electronics work with currents and voltage. Almost every condition is calculable.

If your relay doesn't operate as expected .. there is a reason.
If you show us your circuit, we will find the reason.

For sure we need to know all voltages, resistor values, part names.
There are many relays..some operate with 20mA, others need 200mA.

***
To your problem.
Most probably you didn't take care of enough base current.
Calculate with 1/20 of the relay current.

So if your relay needs 100mA, then the base current should be at least 5mA. (Bjt connected as open collector).
With a 5V drive signal you need a base resistor of below 1k. (Not precisely calculated)

Klaus