When you need to get out of the house but still want to stream music, what options are available? WiFi is one option if you do not go too far. But, what if you could extend your home's WiFi for less than $10? That's why Redditor bethiboothi combined several projects to create an ESP8266-based WiFi repeater. Now, by hanging a small device on a tree, they can stream music from home while jogging!
This repeater's perfect chassis, found on Thingiverse, turned out to be a 18650-sized lithium polymer battery holder with space for an integrated charger. Instead of using the original design's Micro USB battery charger board, bethiboothi put in an ESP-01.
Technically this project is a NAT router and not actually "repeating" the RF traffic. Instead, the ESP-01 runs firmware from martin-ger on GitHub to create an Access Point and NAT router. The phone connects to the ESP8266, and the ESP8266 connects back to the home-based WiFi network.
While the onboard antenna provides a reasonable extended range, a slight modification increases it even further. By soldering an SMA connector to the ESP-01's PCB and connecting an antenna, the range increases to 200 meters. Even more impressive is that the data rate is around 3 Mbit at that range!
A single 18650 battery's expected run time is about three days. Currently, the repeater runs continuously until the battery's voltage drops below 3.2 volts. To protect the cell from an undervoltage condition, the ESP goes into a deep sleep mode.
The total cost for this build is only about $8. For more details on this functional print project, check out this thread on Reddit. You can download the STL for the battery cell/charger PCB holder from Thingiverse and the WiFi NAT (repeater) firmware from GitHub.