DC power supply

The need of static power supply

The need of power voltage supply is mandatory in any mechatronic application. For mobile mechatronic applications like robots, the power voltage supplier must be embedded with the application this can deliver many drawback like for example autonomy.
But when dealing with static mechatronic projects we can just get rid of the battery and use directly the domestic AC power supplier. because this supplier can deliver energy 24/7 with one drawback that this energy must be calibrated to be used in static mechatronic application witch are usually need a DC supply voltage.
In this article I'm going to show you how to create you own DC power supply.

Specifications 

INPUT : 220 V AC

OUTPUT: 5V DC / 1.5A

Principal functions:

 Our board change the 220V AC into 5V DC with a maximum operating current of 1.5A

Current protection : 

we need to protect the board from unpredictable current variation from the power supply or potential shunt that could be very dangerous and can harm our system. The obvious solution is to use a fuse.
The maximum needed current for mini mechatronic applications is 1A with a tolerance of 500mA so any current that exceeds 1.5A would be considered as dangerous to the board and the fuse must interfere. The choice is then a fuse with a normal operating current = 1.5A.

Galvanic isolation and Voltage decreasing

This part of the board is mainly responsible for decreasing the alternative voltage from 220V to 12V alternative current.
For this purpose we need a 220v 12V transformer that can assure both of the functions

Wave rectification

This part of the board is probably the most important, In fact in this part the alternative energy is transformed to a direct one. we need to eliminate the negative part of the wave or replace it with a positive wave.
For this purpose we need a full wave rectifier composed by 4 1N4001 Diodes:

Filtering and smoothing

The rectified wave still need to be more smoothed so I have to fill the gaps between the waves. To do so we need to add a capacitor that able to store voltage and release it in time to fill the gaps.

The specifications needed for our board are :

Vin :regulator input = 12V / Operating current = 1A

C = I * detlta(T)/delta(V) = 3333µF we take it as 4700µf or 2200µF

Voltage regulation

At this step we have a decent 12V DC but it's not really stable and we need to get the 5V DC To feed the electronics. For this purpose we have to add a 5V voltage regulator that can transform 12V to a stable 5v DC. The perfect choice is LM7805 witch is a 5V DC/DC regulator that is capable of supporting up to 1A witch is acceptable for the usual applications. It's recommended to add another filtering capacitor of 10mF in the output of the regulator to assure stabilization.

Integration of the hole design with Altium designer: