Circuit Review (Noise)

Other Hardware General Electronics
1

I am making a automatic water dispenser (schematics attached) using DC motor, solenoid and IR sensor module (https://robokits.co.in/sensors/ir-a...MIjbWz7Krm6QIVVwQrCh1H9gv2EAQYAyABEgJoCPD_BwE).

Submersible Dc Motor pump: 3-6V DC 100-220mA. Driven by 2NAAAA2 transistor.
Solenoid Valve water: 12V DC(rated 0.6Amps). Driven by TIP120 transistor.
5V IR sensor module connected to input pin of arduino.

The system is powered by 12v DC adapter.

Now, I want to make sure that the noise from the motor or solenoid doesn't affect the other components in the circuit. What other components (resistors, capacitors, etc) should I add at different points of the circuit to avoid noise ? Is some sort of RC filter needed to be added to the IR sensor output pin going to the arduino input ?

Also, I am planning to use a bigger 24V DC motor pump (rated 2Amps) in place of existing DC motor pump for another project. What precautions to be taken in this case to avoid noise?

Or is a two channel relay board (probably the ones with optocouplers) a better option without transistors?

And I am planning to add a 250V 2Amp glass fuse for overcurrent protection along with a diode (IN4007) for reverse polarity protection between the power supply adapter and the LM7805 IC.

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2

Read this:

Dealing with motor noise

3

OP image:

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The cathodes of the kickback diodes should be connected to the +motor supply.

A NP 1uF capacitor across the motors would also be recommended.

A relay to fully isolated more powerful motors may also be warranted.

4

Use 1 to 10nF ceramic only across the motors. 1uF is far too high and will cause large current spikes and noise every time its switched on. The capacitor across the motor quenches RF interference from arcing on
the commutator, and even 1nF is a heavy shunt at RF. Must be ceramic type, must be right on the motor
terminals with shortest leads possible.

5

For small DC MOTORS, a 0.1 uF cap between motors terminals is normal, and one 1uF to .47uF cap between each terminal and case works well. As mentioned a ceramic capacitor is recommended.

Both a scope on the power lines and/or a near by radio can be used to monitor the effectiveness of the capacitor value you select.