Hall Effect Motor

7/28/2019 Hall Effect Motor

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Motor on a Hall Effect SwitchDifficulty level: 2 (simple, but requires the use of a soldering iron)Kits covered: Kits #6,8

This is a simple and probably the most reliable motor. You may take a look at how easy it is toassemble this motor from the kit.

In 1879 Edward Hall placed a thin layer of gold in a strong magnetic field. He connected a battery to

the opposite sides of this film and measured the current flowing through it. He discovered that asmall voltage appeared across this film. This voltage was proportional to the strength of magneticfield multiplied by the current. This effect bears his name.

For many years the Hall effect was not used in practical applications because the generated voltage inthe gold film was extremely low. However, in the second half of the 20th century the mass production

of semiconductor chips started. Chips based on the Hall effect became inexpensive and widelyavailable.

The Hall effect IC (integrated circuit) is a very small chip which includes many transistors. It consistsof a thin layer of silicon as a Hall generator (which works better than gold) and several transistorcircuits: to amplify the Hall voltage to a necessary level; to trigger output voltage with its growth;and to provide stable work regardless of the power supply voltage changes. The picture below

demonstrates the Hall effect IC (between the coin and two power transistors):


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The Hall effect IC is a solid state electronic device with no mechanical parts and therefore it is morereliable than a reed switch. To no surprise it is now the most widely used sensor in industrialbrushless motors. Normally, however, they include a lot of other components. I tried to design amotor on a Hall effect switch with minimum parts based on the same unified mechanical design and it

worked very well.

The Hall effect IC used in Kits 6 and 8 (or available as a separate part) is a unipolar switch. It turnson and off when the South pole of the magnet passes by its branded side. The North pole has no

effect on it, unless it approaches from the back side of the Hall IC. This Hall effect IC has a built involtage regulator and may work in the range from 4.5 to 24V. The Hall effect IC's included in the kit,

however, were tested extensively; and I found that most of them start working at 3V. This is a typicalHall effect IC shown from the branded side:

The Hall effect switch output current is not sufficient to power this motor, therefore it also requires apower transistor. You may find information on this component at How It Works: Reed Switch MotorWith A Transistor.

This is how this motor works:

1. When magnet #1 gets close to the Hall IC, the sensor sends a signal to the base of the powertransistor. The transistor opens, and allows a bigger collector current to flow through theelectromagnet. The electromagnet pushes magnet #3 away.


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Difficulty level: 2 (simple, but requires the use of a soldering iron)

Parts included in this kit

Printable version of this page (if you need to print these instructions).

If you want to purchase one of these inexpensive and simple kits, click here.

If you want to understand how it works, click here.

Read all instructions carefully and check the Safety Rules before you start!

Instructions

1. Insert the T-pin into one of the caps.

2. Insert the rotor core into the same cap as shown below. Apply some pressure to push therotor core approximately 1/2" (10-12mm) into the cap.


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3. Put in the wooden insert.

4. Insert the pushpin into the other cap.

5. Put everything together as shown below. Push the caps towards each other until they cannotmove any more. The T-pin must be secured firmly. This process may require some strength.

Be careful not to bend the T-pin or poke yourself.

6. Glue the magnets to the flat surfaces of the rotor core with the letter S facing outside. If youpurchased the kit with 4 magnets and want to try 2 magnets first, glue them to the oppositesides. Straighten the T-pin if necessary. You can check it by spinning the rotor between yourthumb and index finger. Again, be very careful.

All kits have magnets with the South pole marked. If you want this side to look better youmay cut out the white glossy round labels that are provided and paste them to the marked

sides. You may do it before attaching the magnets to the rotor. It is recommended to use

regular white glue or a glue stick on the labels for better results.


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7. Insert the rotor into the stands marked with blue and silver stars as shown below. Hold thestands and test to see if rotor spins freely. Make final adjustments to the T-pin if necessary.

8. Glue the stand with the silver star to the board. Try to cover the corresponding starcompletely. Align the marks on the stand with the line on the board as shown below. Note that

the star's position and the marks are approximate, sometimes you need to move the standsslightly to achieve the lowest friction. Keep in mind that super glue bonds instantly, so try tobe as accurate as possible in these procedures.

9. Insert the rotor into the stand marked with the blue star. Glue it to the board the same way asthe first stand. Leave a gap of about 1/16" (1/32", or 0.8mm on each side) between the rotorand the stands. Test again to see if the rotor spins freely. At this time, or later, you may take

the rubber plug and fix it as shown below. You can glue different things to the outer flatsurface of the plug. Try to be accurate, redo this step if necessary.


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10.If you purchased the experimentation kit #2 or #3, instead of steps 10-12 for this kit, followthese instructions. After that, please, come back to this page and continue the assemblyinstructions from step 13.

Otherwise, insert the nail into the stand with the green star. Apply glue as shown below.

11.Use all of the spool of magnet wire to wrap around the area between the tape and the head ofthe nail. Try to be as accurate as possible. Tape the end and beginning of the wire using thesame tape and leaving open ends of wire about 6" (15cm) long. Do not let the wire slide offthe end of the electromagnet. Clean about 3/8" (10mm) of the wire tips with fine sandpaper(included) or a sharp knife to remove the insulation.

12.Glue the electromagnet to the board as shown below. Turn the rotor slowly to see if themagnets hit the electromagnet. If one or more do, move the electromagnet back until there isa 1/16" (1.5mm) gap between the electromagnet and the closest magnet on the rotor.

13.Bend the leads of the Hall effect switch as shown below. If your kit includes 1 large piece ofhook-up wire, cut it into 4 pieces of equal length. Strip about 3/8" (10mm) of insulation oneach end of these wire pieces using a sharp knife. Solder three wire pieces to the Hall effectswitch. If you did not use a soldering iron before it is a good idea to practice on soldering twopieces of wire to each other. See the Links page for tips on soldering.

IMPORTANT: Do not overheat the Hall effect switch when you solder it. The soldering iron heat


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may destroy this sensitive device. If you were unable to attach the wire in 3 seconds, let theHall effect IC to cool off, then try it again. Only solder one lead at a time and allow the deviceto cool before soldering the next connection. Use the same precautions when soldering the

transistor.

14.Bend the Hall effect switch leads 90 degrees with branded side facing outside:

15.Insert the Hall effect switch into its stand. Make sure that the leads of the Hall effect IC do nottouch each other. You may add a drop of glue to keep the IC and wires in place. Glue only theleads, do not glue IC case to the stand.IMPORTANT: It is recommended to glue the Hall effect IC to the stand as a last step after the

motor is assembled and the best Hall effect switch position is found.

16.Glue the Hall effect switch holder to the board. The Hall effect switch should be located in frontof the magnets at the distance of about 1/8" (3mm) or closer. Check the rotation of the rotorto make sure that the magnets do not hit the Hall effect switch.


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17.Attach the battery holder to the board. The battery holder allows you to experiment with 3different voltage settings (3, 4.5, and 6V DC). You will need 4 AA size batteries. Note that thismotor does not work on one 1.5 V battery. The kit may contain 2 metallic inserts (they looklike medium size nails) or a jumper wire - short piece of wire with no insulation on both ends.

A. If your kit contains inserts simply replace any battery for a metallic insert to lower the voltage,and replace a metallic insert for a battery to increase the voltage.

B. To understand how the jumper wire works let's look at the connections inside the batteryholder:

The following diagram shows how to get 3, 4.5, and 6 Volts using 2, 3, or 4 batteries and a jumperwire shown in blue color. Arrows show the current flow for 3 and 4.5 Volts settings. Could you trace

the current when all 4 batteries are inserted (there is no jumper wire in this case)?


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Insert bare ends of the jumper wire between the spring and plastic case to make a good contact andhold them in place. This is how the jumper wire is actually used for 3 Volts experiments (one end isdisconnected and may serve as on/off switch):

18.Locate the base (B), collector (C) and emitter (E) leads on the transistor:

19.Follow these steps using the wiring diagram for Kit #6 below. You may trim the wires ifnecessary.

If you do not plan to use a heat sink you may glue the transistor with branded side up to theboard using a small drop of super glue.

Solder one end of the remaining piece of hook-up wire to the collector of the transistor. Solder the other end of that wire, the negative (black) wire of the battery holder, and the wire

that is connected to "ground" lead of the Hall effect switch together. It is easier to solder this

connection if you twist the wires together first. Solder the wire from the "output" lead of the Hall effect switch to the base of the transistor. Solder the "supply" lead from the Hall effect switch to the positive (red) battery holder wire. Before soldering the electromagnet wires insert the batteries into the battery holder. Briefly

connect one of the electromagnet wires to the positive (red) battery holder wire and the otherelectromagnet wire to the emitter as shown below. If the electromagnet doesnt repel thepermanent magnets away, switch the wires.

If the motor works, remove the batteries and solder these wires.


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Start with 3V. If the motor does not work, increase voltage to 4.5V. If it still doesnt work, ensurethat the rotor can rotate freely and check all the connections it is important to clean the insulation

thoroughly before soldering. Make sure the batteries are fresh and connected properly. If the motorstill does not work click here for troubleshooting.

CAUTION: Do not leave the motor connected to the batteries if the rotor is stalled. High currentthrough the transistor will make it very hot. It may burn your fingers if you touch it and eventually

may destroy the transistor.

Our experiments showed that the speed of this motor could be controlled by an extra magnet thesame way the speed control unit works for reed switch motors (see Assembly Instructions:

Experimentation Kit #1 and How It Works: Reed Switch Motor). You may buy a speed control unit orjust an additional magnet at our ordering page.

Troubleshooting

This is a recommended troubleshooting sequence for all motors:

1. Make sure that your rotor spins freely if you give it a slight push with your hand.2. Test your electromagnet. Connect one 1.5V battery to electromagnet wires briefly. The

electromagnet should push the closest magnet on the rotor. The rotor should turn 45 if youhave 4 magnets on a rotor, or 90 if you have 2. If it does not - switch the wires.

If your electromagnet does not work, it may be shorted. Sometimes re-winding theelectromagnet may solve this problem.

3. Select the troubleshooting table that corresponds to the motor you are trying to assemble andfind your problem, cause and solution:

Kit #6:

Problem Cause Solution

Newly assembled motor does notwork: rotor does not spin.

Rotor is jammed. Find the exact cause andfix the problem. This mayrequire breaking off the

stands and reattachingthem to the board. Youmay try to lubricate theaxles with WD-40 or any

other lubricant.


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Electromagnet attracts themagnets instead of repellingthem.

Switch the electromagnetwires.

Bad connection in wiring. Thoroughly clean thewires to remove theinsulation before

soldering. Re-solder theconnections.

Intersecting connections inwiring.

After soldering check allthe connections to makesure that they do not

touch each other.

Hall effect IC is too far from therotor.

Move the Hall effect ICcloser.

Hall effect IC is facing the wrong

poles.Branded side of the Hall

effect IC should face theSouth poles of the rotor

magnets; or back side ofthe Hall effect IC should

face the North poles.Change the Hall effect ICorientation or re-glue themagnets.

The battery is dead or batteryvoltage is low.

Get a new battery.Increase the voltage byadding an extra battery.The lowest voltage for this

motor is 4.5V, thoughsometimes it starts at 3V.

One of the magnets is notrepelling.

Tear this magnet off andglue it upside down. All of

the magnets should havethe same pole facingoutside.

Rotor is in a "dead spot" themagnet is outside of the Halleffect IC working range. Usually

occurs if you tried 2 magnets ona rotor first.

The rotor will not startspinning on its own. Giveit a slight push.

The transistor is connectedincorrectly.

Make sure that youconnected transistor leads

according to the wiringdiagram.

The transistor was burnt anddoes not work. This may happen

if you overheated it whilesoldering, connected it

improperly, or had the rotorstalled on a high voltage.

Replace the transistor.


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The Hall effect IC is connectedincorrectly.

Make sure that youconnected the Hall effectIC leads according to the

wiring diagram.

The Hall effect IC was burnt anddoes not work. This may happen

if you overheated it whilesoldering, connected it

improperly, or used highvoltage.

Replace the Hall effect IC.

The battery is dead or battery

voltage is low.Get a new battery.

Increase the voltage byadding an extra battery.The lowest voltage for this

motor is 4.5V, thoughsometimes it starts at 3V.

The transistor is burnt. Get a new transistor andre-solder it. Try not to

leave the motor stalled,this may be a reason thetransistor was burnt in thefirst place.

Motor worked fine for a while but

then stopped working.

The Hall effect IC is burnt. Replace the Hall effect IC.

The rotor has too much friction. Make sure that the rotorspins freely. You may adda heat sink to thetransistor for better heat

dissipation. You may alsotry to lubricate the axles

with WD-40 or any otherlubricant.

The transistor is getting too hoteven when the motor works.

The Hall effect IC stays on mostof the time.

Move the Hall effect ICfarther from the rotor.You may add a heat sinkto the transistor for better

heat dissipation.

Not enough wire used for the

electromagnet.

Make sure that the

electromagnet coil hasenough wire. Use almostall the wire from the

spool.

The electromagnet gets hot.

Short connection inside theelectromagnet.

Re-wind theelectromagnet. It is betterto use a new spool ofwire, but sometimes the

old wire may still work.

If you need to disassemble the

rotor

This operation requires

quite a bit of strength.


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Disassemble the rotorwith a rocking motion as iftrying to break it and at

the same time pulling theends out.

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Hall Effect Motor