Update - 22.01.2020
Here is my schematic. I tried to use all of the comments guys below:
Should I use a fly-back diode as commented after I cleared the schematic? If yes, where?
Is it required to protect the Arduino or any part of the circuit in this diagram?
If the solenoid used 24V DC in this diagram, will 24V DC reach my Nano and damage it? If yes how to protect it?
Is the circuit protected from using both way to open the solenoid accidentally by finger print and the push button of the headset? If no how to do that?
Here is the post before update to the schematic:
I am a newbie to electronics, but I did read for a long time and search but this is my first circuit it may look easy for you but I need help.
Here are two schematics and I need them to be joined together with op protection and reverse voltage protection as well.
The project is a solenoid door lock I will add a finger print module operated with Arduino Nano to open it.
In fact, the solenoid is operated by normal doorbell intercom, so the project here is to make both ways to open the solenoid the fingerprint module and the intercom.
- The solenoid needs 1.8amp to open.
- Reverse voltage protection due to the power will come to Arduino when solenoid opened from the intercom.
- I have a TIP122 transistor if needed.
- Arduino Nano will be used in the project.
- Pin 9 or any will be used to send a signal to the transistor to pass the power required to open the solenoid.
- Over 12V protection for Arduino Nano if dual input power source will be used.
Normal intercom button should open the solenoid.
- Fingerprint module read the fingerprint
- Arduino Nano received the data approved then send a signal from pin 9 to transistor TIP122 to open
- Transistor TIP122 opens and passes the current to open the solenoid.
- The finger print module goes into sleep mode if no activity for specific time.
Please try to consider the size of the circuit if possible need to be a small or good size to be placed behind the door of the house.
I need to know how to connect these both isolated circuit to do one work which is open the solenoid without conflict with each other if both power used intermediately?