DC-DC converter power supply for the PCB

A project log for Cheap Ethernet IO extension board for smarthome

Cheap low power smarthome extension board with Ethernet/Modbus/1-wire/DMX512/Wifi connection

markbngmarkbng 07/17/2017 at 23:250 Comments

This week I will start with the board. Today I made the power supply for the unit. I wanted a synchronous DC-DC converter with a high efficiency. The voltage difference between 24VDC and 3V3 is a lot. It's a waste to burn the 20,7V up in heat. That's why I want a DC-DC converter with a high efficiency. So the DC-DC converter must also be able to handle the 24VDC input voltage. I want to generate 3.3V and 5V. The ethernet device ENC28J60 uses a lot of power and also the ESP-12 that is on the board. I will also make it possible to have the ENC28J60 and BLE on the board. But you have to choose: WiFi or BLE (due to the restrictions of number of SERCOMs. a shared sercom for both devices). I will use the Ethernet mainly, so maybe I will go for the BLE option. The BLE module is the JDY-10 (it is $1.38 on aliexpress with shipping).

But back to the task of today. The power supply of the PCB. To be safe I calculated the DC-DC to be able to handle a 500mA output current.