USB Cable Power Tester
Posted: Tue Mar 02, 2021 10:47 pm
Over the years, I have purchased many USB micro cables and USB iPhone charging cables. Some of these have been at the famous Shenzhen Electronics Markets, where you can find them stacked up high:
Many of us touring there wondered if we could design up a simple cable tester, sop we could check the cable quality before purchasing the cable. I know you can buy them, but I wanted to make my own PCB for this. The other day I was mindlessly swimming some laps and out of nowhere a design for placing a cable under various loads popped into my mind. It made for a wonderful swim.
The idea is, that a processor will measure the USB battery voltage and current coming into the PCB. It will then be routed out to the USB cable under test and the other end will be plugged into the board and the voltage at the other end will be measured as well. Therefore, I know how much current is flowing through the cable and the voltage drop across the cable, so Ohms Law says R = V/I, so I now know the cable resistance.
This initial design is what I call an Engineering prototype, so I have various testing points across the board and I can switch in three different loads through the cable. I can also connect the USB battery directly onto the three loads, so hopefully I can test the battery load capacity as well. If this all works out well, I can then minimise the resistor load and change the ESP32-WROOM-32D processor board to something cheaper, as this project doesn't really need to be WiFi or Bluetooth enabled!
However, it's a buyer beware market. Size and looks count for nothing. One year, just to prove a point I purchased three fat USB cables all 'Good Quality' or so I was told. Back at the Shenzhen Steamhead Makerspace, I cut them open and yes, as expected, I found that all of them had very thin internal wires inside - coated with a fat layer of silicone plastic. Many of us touring there wondered if we could design up a simple cable tester, sop we could check the cable quality before purchasing the cable. I know you can buy them, but I wanted to make my own PCB for this. The other day I was mindlessly swimming some laps and out of nowhere a design for placing a cable under various loads popped into my mind. It made for a wonderful swim.
The idea is, that a processor will measure the USB battery voltage and current coming into the PCB. It will then be routed out to the USB cable under test and the other end will be plugged into the board and the voltage at the other end will be measured as well. Therefore, I know how much current is flowing through the cable and the voltage drop across the cable, so Ohms Law says R = V/I, so I now know the cable resistance.
This initial design is what I call an Engineering prototype, so I have various testing points across the board and I can switch in three different loads through the cable. I can also connect the USB battery directly onto the three loads, so hopefully I can test the battery load capacity as well. If this all works out well, I can then minimise the resistor load and change the ESP32-WROOM-32D processor board to something cheaper, as this project doesn't really need to be WiFi or Bluetooth enabled!