USB power lead

The USB power lead can be used to power an MP3 amplifier and it is something we have tried without a problem.

Having said that the amplifier's performance is better at higher supply voltages. This is because it can only amplify to the maximum of the supply voltage before distorting. You may therefore also want to consider out 12V dc supply which works well. This can be found under the 'Power supplies and USB power' section.

The computer USB is a 5V supply. It would depend on the buzzer you had in mind as to whether it would work. The white piezo buzzers we sell are designed to run off a 3 to 24V supply so would be fine. The lower frequency black buzzers are available in a range of voltages and you would need to use a 6V buzzer is designed to work between 4 and 8 volts so would be fine with the 5V from the USB supply. Both types of buzzer take less than 30mA so would be OK.

The USB interface is a 5v supply and 2 data lines. So if you have a USB device that you need to power it would be possible to use a 5V supply and connect it to the device via the USB port. You are therefore right that with the appropriate adaptor this lead could be used. However DO NOT use a 9V battery as you will damage the equipment that you connect to it. The voltage should be between 4.75V and 5.25V and capable of delivering 0.5A.

The low torque motor you have suggested is a 3V motor that will work up to 4.5V and the USB port is a 5V port. Something that is connected to the USB port should only draw 100mA unless it has communicated with the PC and negotiated a higher current, in which case it can take 0.5A. The typical current of the motor is 1A so as well as being too lower a voltage it will also take too much current. The other thing to consider is that educational motors are electrically noisy and that PCs are more sensitive, though generally this will be the lower voltage supplies rather than the 5V supply.

So in order to keep inside the motor voltage specification and below the USB port current specification I’d suggest using a low inertia solar motor. This will also have the advantage that it is electrically cleaner than the other motors, but it is more expensive. The stock code for this motor is 2506.

The 3.5V lamp will have a bit of tolerance in terms of the maximum voltage, however I'd expect that this might be 10% above the rated voltage of 3.5V. It certainly isn't specified to run at 5V, so no it won't work. Depending on the application, you might be better using a white LED as it will use less current and it's easier to operate at the required voltage by means of a current limit resistor.

For more details see white LED USB lamp in the related products link.

Yes the low inertia motor would be fine to be used with the USB lead, as well as being low voltage it is also low current at about 10mA. The question as to if it would work with our solar cell is a little more tricky to answer. If the application doesn’t load the motor, for instance using it as a fan then it should be fine. However if you plan on driving something where the motor is going to be under a heavier load I’d definitely give it a try before deciding if it’s a good idea. All solar cells are specified to make them look good and if they once managed to do 5V at 50mA then that is what they will be quoted as. You will never manage to get a solar cell to deliver the amount of power the specification suggests it is capable of.