Hi all! I need some help with this design. I want to drive a relay with a transistor. I want to know the correct value of the Rb, and Rc(equivalent) to work on the equations.
I sticked with a 2N2222A to start with, and on datasheet says several hfe values so i dont know which to take ; i know, they are under certain conditions but i want to know if that ic under those conditions is Vcc/Rc or hfe*ib.
All is because the value of Vceo is negative.. :S so i dont know if this is good or im missing something. The only way i think is to increase the value of Rb like 100k-150k.
Vbb is 5v from a PIC16F84A, like 12 ma out of each pin of PortB (100ma out of all pins).
Vcc say is 20v DC for a relay rated for 24V , 2888 ohm coil res, 8ma max.
I've seen other circuits and RB ranges from 1k to 240k (1k, 4.7k, 10k, 100k..)
Ill attach the part of the circuit.
Thanks!!!!
I sticked with a 2N2222A to start with, and on datasheet says several hfe values so i dont know which to take ; i know, they are under certain conditions but i want to know if that ic under those conditions is Vcc/Rc or hfe*ib.
All is because the value of Vceo is negative.. :S so i dont know if this is good or im missing something. The only way i think is to increase the value of Rb like 100k-150k.
Vbb is 5v from a PIC16F84A, like 12 ma out of each pin of PortB (100ma out of all pins).
Vcc say is 20v DC for a relay rated for 24V , 2888 ohm coil res, 8ma max.
I've seen other circuits and RB ranges from 1k to 240k (1k, 4.7k, 10k, 100k..)
Ill attach the part of the circuit.
Thanks!!!!