Difficulty level: 1 (the simplest, no special tools required)
Kits covered: Kits #1-4, 8-14 and “Reed Switch Motor Made with Household Materials”

Motor, assembled from the kit

If you do not know much about electric motors, we recommend building this motor first. It is the simplest motor with some real practical applications and it works very well. You may take a look at how easy it is to assemble this motor from the kit you may order.

Most simple motors described either in books or on the Internet (see Links) aren’t stable, reliable, or powerful enough. Usually the brushes in these motors cause the problems. (In simple conventional motors the coil spins in a magnetic field and moves between two sliding contacts called brushes.) It is quite hard to make this part of the motor accurate and reliable without having special tools, materials, and skills.

Actually almost all of them are not real motors – nothing can be connected to them!

In 1997-2000 Stan designed and built for a school science fair project a brushless motor, in which the permanent magnets (this is the rotor) spin and the coil (this is the stator) doesn’t move. The reed switch was used to sense the position of the rotor and to change the magnetic field of the stator at appropriate times. This page explains the principles of Stan’s original design, which provides excellent results despite its simplicity.

A reed switch consists of two magnetic contacts in a glass tube filled with protective gas:

Reed switch

When a magnet comes close to a reed switch the two contacts become magnetized and attracted to each other allowing an electrical current to pass through. When the magnet is moved away from the reed switch the contacts demagnetize, separate, and move to their original position.

Reed switches are very reliable and last as long as 3 billion operations if used properly. They are designed for low currents. High voltages applied to the contacts may cause a spark, which may weld the contacts together. The best solution to this problem was recommended by one of our visitors, Karl Mueller from the University of Michigan. He suggested to use so called ZNR’s. The ZNR is a little electronic device that absorbs voltage and current spikes. It connects parallel to the reed switch and practically eliminates the spark inside the reed switch glass tube.

This is how the reed switch motor works:

  1. When magnet #2 gets close to the reed switch the two contacts inside the glass tube get magnetized and touch each other. This causes the electromagnet to push magnet #1 away.

    How reed switch motor works - diagram 1

  2. When the magnets spin away, the reed switch demagnetizes and gets disconnected. This creates an open circuit disabling the electromagnet.

    How reed switch motor works - diagram 2

  3. The magnets continue to spin due to inertia until magnet #1 gets in working range of the reed switch. It becomes magnetized again and its contacts connect together making the electromagnet push magnet #2 away. This process continues until the power source is disconnected or depleted, or the reed switch is moved out of working range.

    How reed switch motor works - diagram 3

New! Watch How Reed Switch Motor Works video on our YouTube channel.

This motor can be built from Kits #1-4 or #11-14. If you decide to build this motor yourself, you may order only the parts you need (reed switch, magnet wire, magnets, ZNR). If you are a novice it is strongly recommended to use large and powerful reed switches in your designs as smaller reed switches are extremely fragile, may not last long enough, and it is difficult to connect them without soldering their leads. We offer hard to find heavy duty reed switches that are appropriate for beginners.

The reed switch motor has a unique advantage. It is very easy to control and change its speed with a few additional parts. If you take an extra magnet and bring it closer to the reed switch, its magnetic field will change the gap between the reed switch contacts. A smaller gap allows the contacts to switch faster and therefore the speed of the motor will increase, and vice versa.

Variable speed reed switch motor

This allows you to control and change the speed of the motor from a complete stop to maximum speed, which may be 10-25% greater than the normal speed of the motor.

You may move the magnet as shown above or rotate it near the reed switch. The following diagram shows how different positions of an extra magnet affect the speed of the motor:

Speed control magnet

Orientation of the speed control magnet is very important. If it is oriented improperly the reed switch contacts may get connected permanently. It will create a short circuit, which may overheat the wires and drain the battery quickly. It may also destroy the reed switch.

The speed control kit can be added to the reed switch motors kits #1-5 and #8-9. It is included with kits #10 and #13-14.


  1. Hello we built this motor in our class, however we did not use the znr. We tried getting resistance readings and current readings but nothing really added up to our calculations done on paper. We attributed this to battery resistance, but I was wondering if our readings would get screwed up by the reed switch.

    It would be great to hear your opinion of the matter.

    Overall though this was a great way to learn about motors and how they work.

    Thank you ,

  2. I presume ZNR means”zener diode”.
    If so, why not use just an ordinary diode to absorb the inductive fly back current.

    PS: Thanks for the information on how many cycles a magnetic read switch can deliver.

    • You can use a regular diode. Stan used 1N914 – see his third year study at https://simplemotor.com/pdf/research-2000.pdf (pp.19-20). It provides some reed switch protection.
      However in his future experiments ZNR provided better results.
      ZNR is not a zener diode. ZNR is a term used by Panasonic who makes them and is defined as ZNR Transient/Surge Absorber. I believe it is metal oxide varistor which is a passive element with no polarity.

  3. Thank you for your site page very clearly stated on this little motors operation, and tuning.

  4. Amazing YouTube video. The words were very nice as well but an actual person really helped me understand it very well.

    • We are. All the information on our website is original and copyrighted.

      Serge and Stan Pozmantir

  5. I am making this for my science project

  6. Hello, my magnets are not all making a clicking sound, therefore it is not working

    • I assume you did not buy these parts from us because our parts are guaranteed to work. Possible explanations for your problem:
      1. Your magnets are not strong enough to activate the reed switch
      2. Your reed switch is too small and clicking sound is not loud enough to hear it
      3. Reed switch is defective
      4. Magnet is too far from the reed switch or located in the middle of the reed switch.

      Best regards,
      Serge Pozmantir
      Simple Motors, LLC

  7. What rated ZNR surge absorber is good enough for using on this motor? Or for a 9,12, 24 volt, electromagnet motor setup?

  8. Can I buy a couple of ERZ- V05D820 varistors from you?
    If so I will need your address and the cost with shipping included to Canton, Michigan 48187
    Many Thanks

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