Test Setup ESP2866 ESP-12 HC-SR04 on Batteries

I’m currently building a sensor based project, where a sensor needs to gather data every hour, and send it to a server, I first thought it would make sense to use an arduino board, connect a wifi shield and set the thing up.

The problem is I will need around 40 of these small sensors and arduino boards and wifishields will increase the price of this project, so I decided using a ESP-12 wich is a self contained SOC with integrated TCP/IP protocol stack that can be used to give any microcontroller wifi access, or as a standalone module which hosts it’s own application.

This is great since they cost only around €5,- and I’m able to connect my sensor directly to it, and let the esp-12 send the captured data to my server.

What I used for my test setup

• ESP-12
• FTDI Basic Breakout – 3.3V (the ESP-12 needs 3.3v not 5v, keep this in mind, since a lot of people fried their module)
• 470 uF capacitor
• Breadboard
• Jumpercables
• 4-channel I2C-safe Bi-directional Logic Level Converter – BSS138
• LM2596S DC-DC adjustable output step-down module (It’s a bulky thing but will do for the prototype)
•  I have added a 470uF capacitor at the beginning of the power input
• I added a 0.1uF cheramic capacitor between the vcc and gnd of the hc-sr04
• I added a 470uF capacitor at the power input before the ESP12E and the LLC

Picture of the breadboard setup:

When using my arduino uno as a power source (the 5v is pushed in on the lef top side, where the HC-SR04 is getting it’s power from, the 5v is being stepped down to 3.3v with the LM2596S.

I have tested it with 3 eneloop batteries too, everything worked like a charm, even though the output voltage was on the low side (4v, HC-SR04 expects minimum of 4.5v, but it seems to work fine)

This was a great learning experience, for now I will use this setup to create the software that I want on the devices, and have someone design the pcb for production since I don’t have enough knowledge of pcb design or electronics for that matter, it will be best to leave it to someone who can further compact my setup into a pcb solid pcb design.

Update: I have received the final pcb version Check it here