I have received a lot of great help on this site now I need help choosing a transistor for my project.
I am using a controller with a 5v output and some transistor to switch a relay. The manufacturer of the controller said to use a 220-440ohm resistor on the base of the transistor. The coil of the relay is powered by 9v and is 500ohm so Ic=9/500= 18mA. I am got sure if i am calculating hfe correctly. I came up with a value of around 8 using a 440ohm resistor on the base. Will a bc107 NPN transistor work?
https://www.st.com/stonline/books/pdf/docs/9293.pdf
Also, will a 10kohm resistor on the emitter prevent leakage when the transistor is off? Just making sure I am on the right track.
I know I need a protection diode on the coil. What do i need if the relay contact is seeing 24vdc, max 8A?
Thanks
I am using a controller with a 5v output and some transistor to switch a relay. The manufacturer of the controller said to use a 220-440ohm resistor on the base of the transistor. The coil of the relay is powered by 9v and is 500ohm so Ic=9/500= 18mA. I am got sure if i am calculating hfe correctly. I came up with a value of around 8 using a 440ohm resistor on the base. Will a bc107 NPN transistor work?
https://www.st.com/stonline/books/pdf/docs/9293.pdf
Also, will a 10kohm resistor on the emitter prevent leakage when the transistor is off? Just making sure I am on the right track.
I know I need a protection diode on the coil. What do i need if the relay contact is seeing 24vdc, max 8A?
Thanks