Details

This board takes AC mains input from 100V to 250V AC and output regulated +5V DC providing current up to 50mA. Great for running small application 24x7 due to low cost, power saving and almost zero heat generation.

In most non-battery applications, the power to the microcontroller is normally supplied using a wall mounted transformer, which is then rectified, filtered and regulated. In most applications, this method of generating the regulated voltage is cost effective and can be justified. However, there are applications where the main controller and low voltage is not required by other components except the microcontroller in application. In these instances, the cost of the transformer becomes the sizable cost factor in the system. For example, most fire alarms & round the clock monitoring alarms are powered this way.

Transformerless power supplies, thus, have a distinct advantage in cost as well as in size. The disadvantages of using a transformerless power supply are low current supply and no isolation from the AC line voltage.

The microcontrollers usually draw a maximum of 20 mA, even at the highest frequency and voltage of operation, therefore low current availability is not an issue. The main disadvantage of transformerless supplies is that they don't offer isolation from the HV line.

One down side of this circuit that it is not isolated from mains so it should not be used in applications requiring touch of any contact from user. If any part even though +5V side is touched it would cause shock to the user. Please be careful about touching when using it during experiments or final applications.

Warning! An electrocution hazard exists during experimentation with transformerless circuits that interface to AC mains wall power. There is no transformer for power-line isolation in the circuit, so the user must be very careful and assess the risks from line-transients in the user’s application. An isolation transformer should be used when probing the circuit during experimentation.