USB Confusion

USB Confusion

Do you find USB confusing? This LAZY OLD GEEK (L.O.G.) will try to simplify some of this.

********************FIRST TIP*******************************

When you get a USB device, I would strongly recommend you label the Wall Wart and the cable so that you’ll know what they are designed for.

*********************FIRST TIP*******************************

The reasons for this First Tip are many. Most cables provided with devices have a specific type of USB connector on one end and another USB connector on the other. They are designed to interconnect the source and the device so the best power is supplied. They can be confused with other cables that look similar but may not work the same.

I like to use cable label tie wraps but you can also use masking tape and a Sharpie or even paper and scotch tape. Wall Warts can be marked with a Sharpie or masking tape. See pictures.

USB Basics:

The first function is to provide power from the source, e.g., Wall Wart to the device, e.g., Smartphone.

The optional second function is to provide communications between the source and the device, e.g., computer to Smartphone. Typically this is data communications but sometimes it is handshaking where the device tells the source what type of power it needs, e.g., Pixel Wall Wart to Pixel Smartphone.

Wall Warts are one of the most common USB sources. They plug into the wall and supply power. See previous picture.

CONFUSION #1

Wall Warts have two different types of connectors called Type A and Type C. See pictures. The cables for these are not interchangeable but both do the same thing, supply power to the device. (The nice thing about the Type C is there is no right side up). Make sure you have the right cable connector type for your Wall Wart and device.

CONFUSION #2

The other end of the cable usually has another USB connector. The three most common types are USB micro, USB C and Lightning. See picture.

Especially for Old people with bad eyes, it’s easy to confuse them. The first, the micro has a right side up and may have to be rotated 180degrees to get it to work. The second, C has no right side up, the same as the third, Lightning. The Lightning is only used on Apple products. Make sure you have the right connector type for the source and the device.

CONFUSION #3

The cable connecting the Wall Wart and the device may be for charging only. Specifically a Type A to micro for charging small devices may have only two wires for 5V and ground. This won’t work for higher power charging and communications. There is no visible way to tell the difference, hence FIRST TIP label your cables.

CONFUSION #4

More confusion is that different Wall Warts may supply different voltages and currents.

*************************** TIP********************************************************

No Guarantees, but, as far as I know, connecting any USB source to any USB device will not HARM either one. Without the correct cable and the correct device all Wall Warts should default to 5V which any USB device can tolerate. This does not mean it will work or work at it’s best.

*************************** TIP*********************************************************

If you follow FIRST TIP then you shouldn’t have any problems but I will go into some detail in the next step.

CONFUSION #5

Well, I’m not going to spend a lot of time on communications but here’s a little bit. The next picture shows three USB type A connectors on my PC. The blues ones are USB3.0 and the black one is USB2.0. The USB2.0 has four wires, the USB3.0 has nine. The reason why they look very similar is because USB3.0 is backwards compatible. The main difference between 3 and 2 is the communications speed, 3.0 can transfer data 10 times faster. You will probably notice the difference in transferring files on a USB3.0 external hard drive or USB3.0 flash drive. Make sure the cable also has the blue USB3.0 type A connector.

The next step goes into a little more detail. Ignore if you want.

Step 1: USB Power

Changes in USB power is one of the major points of confusion.

A little simplified electronics:

Voltage: So a single AA battery is 1.5Vdc, if you put three of them in a row, you have 4.5Vdc (1.5 *3). So you basically have 3 times more power. A 3-cell flashlight is usually brighter than a single cell.

Current in mAmps or Amps: Now you may think a C size battery has more current than a AA battery that is not correct. One way you can think of current is a dimmer switch on a lamp. When it’s low there is less current and the light is dimmer, when it is high there is more current and the light is brighter. Again, this is more power.

It is true that a C battery has more current CAPACITY than a AA battery. It will last long drawing the same current. Current depends on the load or device connected to the source.

Power in watts is actually the voltage times the current.

The first USB Sources were fixed at 5Vdc and a maximum of 500mA. This was the standard in personal computers and laptops.

Point of Confusion: If a Source is 5Vdc and 500mA, when it’s connected to a Device, it will always provide 5V but the current depends on the Device. What the 500mA means is that it’s the maximum current. Actual current can be anywhere from 0 to 500mA.

Back to USB Sources, well as devices became more sophisticated, the Sources needed to supply more than 500mA. The industry responded with USB3.0 (the blue connectors) which has a maximum of 900mA.

Needing even more power, Smartphone manufacturers started shipping with Wall Warts designed for the phone.

Some generic Wall Warts may have higher maximum currents and are labeled accordingly, see picture. By the way, cheap Wall Warts don’t always provide the currents they’re labeled as having.

There are limits to how much current the USB connectors and cable wires can handle but smartphones kept getting bigger and more power hungry so they took longer to charge.

So several schemes were developed to be able to increase the voltage while charging.

Two of the most popular are PD, Power Distribution and QC, Quick Charge. I am fairly certain that Apple and Google use PD for smartphones charging.

I have a Google Pixel smartphone.

The next picture show Pixel Wall Wart (PD) with no load on it. The cross shaped device monitors USB voltage and current. The voltage is 4.63V and current is 0.03A. (This cheap USB monitor doesn’t display correct voltage. It’s closer to 4.96V.)

The next picture shows it with my Pixel phone connected to the Wall Wart. The voltage is 8.8V and current is 1.17A. NOTE: my Wall Wart is rated at 5V/3A or 9V/2A but is only using 1.17A. This is because that is all that the Pixel needs at that time. The Pixel says ‘Charging Rapidly’.

By the way, my Pixel will also charge on a regular USB, it just takes longer and it will say ‘Charging’ not ‘Charging Rapidly’.

These newer smartphones are pretty smart in that they will adjust the current and voltage so that the phone and battery won’t get too hot. So the voltage and current may be higher when the battery is depleted, than drop after it’s partially charged.

I own a QC3.0 Wall Wart. Notice without a device connected, it reads ~5V.

The next picture is with it hooked up to QC3 wireless charger, the voltage is reading ~9V. The reason current is 0 is that my earbuds are nearly fully charged.

As a test, I connected my QC3.0 Wall Wart to a USB A to USB C cable and connected my Pixel, it said Charging but was at 5V. That suggests it wasn't the right protocol so defaulted to 5V. (It is possible that cable wasn't correct though)

Miscellaneous Information:

Other USB sources include car adapters, special power strips, power banks. See pictures

The cross shaped USB tester was purchased from AliExpress.com. It is not that accurate but gives you a general idea of voltage and current. Sometimes the power outputs are marked like the PD on the C connector on the power strip and the QC 3.0 label on my Wall Wart. Sometime you can get a clue like the label on my Pixel charger. See pictures.