Attached is my current circuit for using a 5V logic output device to control 24V going to a load with max current draw of 14mA. (Ignore the name for transistor Q1, that is just a random NPN BJT).
The max current draw of the logic source is 300mA (a Velocio e-1450 PLC).
I am new to transistor design and selection, and I would like to know what you consider when choosing a transistor - what range of values do you allow for a given circuit? Should the base voltage be exactly what you expect it to be? (5V rating for 5V logic control, etc.)
Also, are the resistor values relatively ok for the desired output? For R1, I took (24V - 0.3V) / 14mA ~= 1.69 kOhm.
Thanks for your input.
To sum it all up, is this the right design to use 5V logic to power a solenoid (J1) with 24V? Forgetting the resistors and transistor values.
1) The 5V logic output (V1) from the Velocio e-1450 can provide up to 300mA
2) The solenoid (J1) draws max 14mA.