String wave machine - electronics help needed

Projects
1

Hi all. I am making this: https://www.exploratorium.edu/snacks/string-machine
I don’t want to use D cell batteries, so I am hoping to power it via a USB charger.
The charger outputs 5V and the motors are rated for 1.5 to 3V.

I know how to create a voltage divider to reduce the 5V to 3V.
However, since there is a potentiometer in the circuit, could I change the potentiometer to one with a higher resistance in order to ensure that the voltage doesn’t exceed 3V?

As you can see, my understanding of electronics fundamentals is not where I would like it to be :frowning:

2

Use a buck converter…

I have a bunch, I will give you one - how many amps do the motors need?

Cheers!

1 Like
3

Thanks. I had thought of a converter, but wanted to keep the build super simple. The “no load” rating for the motors is 0.3A. Since I haven’t bought the potentiometer yet, changing the spec on that would be easiest.

4

These are pretty simple - Voltage in -> You adjust it to what you want out -> Voltage out, and if the IN voltage changes a bit its no big deal, it will regulate it…

5

Hi Brendon.
I think the simplest way is a potentiometer.

Here are some ideas: https://www.quora.com/How-do-I-step-down-5-volts-to-3-volts-Or-can-I-run-my-cheap-e-cigg-on-5-volts

:slight_smile:

6

Hi Claudio! How are you? I like how you pop up in all the good places - Institute of Imagination, OttoDIY and now SLMS! Hope to see you there one day.

I’ll need a circuit in which the potentiometer resistance is such that no matter how you turn it, the voltage doesn’t exceed 3V.

7

Could you connect the two motors in series and then it would be 2.5V across each? Or does that not suit the circuit?

8

Voltage converter is the best solution in terms of efficiency but if you want to keep it super simple use a ballast resistor in series with the motor this will simply limit the maximum current through the motor thus protecting it from the high voltage the speed and torque characteristics of the motor will obviously be affected and and a small wound resistor will get very hot