What can you do with all those used Covid-19 hometests? My proposal is to turn it into a pulse motor on solar energy. In this way you make it into a memory object with a very long runtime. The circuit is very simple. A solar panel, a voltage regulator, a hallsensor, a supercap and a coil, are doing the job.

Supplies

Partlist:

• SM351LT Hall Sensor, A= 360nA, V= 1.65V - 5.5V, SMD

• XC6206 LDO, Q-current 1uA, V-in 6V max, V-out 3V, SMD

• Equivalent IC: Hall DRV5032. LDO: LP2950 V-out 3V, TO-95

• Pulse coil from a 220V AC relay with 12Kohm resistance

• 8 neomagnets 8mm x 4mm and 2 neomagnets 6mm x 2mm

• Solarpanel 5V 60mA

• Supercap 22F or 50F 3V

You need 7 hometest of whereof 2 prepared with magnet bearings.

Step 1: Construction

The pulse motor has a simple construction. The rotor runs with magnet bearings build in the upper and lower plastic test strip. Below a small glassplate I glued a magnet. This keeps the iron rotor shaft in place. The shaft does not touch the upper magnet bearing. As actuator we use a low power Hall sensor. It's also the driver for the coil. A LED shows the activation pulse. This is also used for the fine tuning. I glued the sensor to the coil and moved it until I reached the optimal result. All the test strips are glue'd together with second glue. The solar energy is stored in the super-capacitor. When full, it can power to the circuit for at least a week.

Step 2: Video

Step 3: Some Tips

Making the mechanical part of the pulse motor looks not difficult. The rotor is the most important part because all the other measures and processes are made for it. The rotor shaft I cut off an iron spoke and I made at both sides a sharp point with an angle grinder. Photo's and video show the placing of the parts. The working of the pulse motor depends on the position of the hall sensor. You can slowly turn the rotor by hand and see when the led lights up at the best position. That happens as the rotor magnet is above the coil and is pushed away by the magnetic pulse. The Covid-19 hometest motor runs at ultra low power, below the 100 micro ampere. Without LED power use is even less.