halloween_man
New Member
Hi,
I am learning about PIC microcontrollers and want to drive a 12VDC (9 - 14VDC) pneumatic solenoid Valve (inductive load). The valve is 12VDC and draws 500mA.
I have found the TIP120 darlington transistor and would like to use it as it is inexpensive AND easily replaced if I damage it.
Depending on what web site you find you get many different views on how to implement the use of the TIP120.
The controller output is 5VDC, I want to drive 12VDC with a max of 1 AMP. It appears this can be determined by the resistor that is connected to the base of the TIP120, so many site imply. I often see a 1K resistor in series between the PIC output pin and the base on the TIP120.
First, is a resistor between the PIC pin and the base required, many sites do not show one.
Second, if it is, how do I calculate the proper resistance (ohms) value and power (watts) rating for the resistor?
I have even seen sites that says you need an optoisolator between the PIC pin and TIP120 base.
Third, the TIP120 has a built in "kickback" diode. Many sites still show an external diode - 1N400x across the coil of the inductive load. Is this second diode really necessary?
Please help out a newbie....
Thank you for your time, it is greatly appreciated.
I am learning about PIC microcontrollers and want to drive a 12VDC (9 - 14VDC) pneumatic solenoid Valve (inductive load). The valve is 12VDC and draws 500mA.
I have found the TIP120 darlington transistor and would like to use it as it is inexpensive AND easily replaced if I damage it.
Depending on what web site you find you get many different views on how to implement the use of the TIP120.
The controller output is 5VDC, I want to drive 12VDC with a max of 1 AMP. It appears this can be determined by the resistor that is connected to the base of the TIP120, so many site imply. I often see a 1K resistor in series between the PIC output pin and the base on the TIP120.
First, is a resistor between the PIC pin and the base required, many sites do not show one.
Second, if it is, how do I calculate the proper resistance (ohms) value and power (watts) rating for the resistor?
I have even seen sites that says you need an optoisolator between the PIC pin and TIP120 base.
Third, the TIP120 has a built in "kickback" diode. Many sites still show an external diode - 1N400x across the coil of the inductive load. Is this second diode really necessary?
Please help out a newbie....
Thank you for your time, it is greatly appreciated.