DIY Magnetic Hall Effect Sensor, build one.

Jeff Nading

DIY Magnetic Hall Effect Sensor, build one.
« on October 19th, 2014, 05:29 PM »Last edited on October 19th, 2014, 05:39 PM
Ok all of you who don't want to pay the price and search the internet for days looking for a Magnetic Hall Effect Sensor. I did find two, one on eBay and one here,

In my searching I found something I had forgotton about, so thought I would share this with every one who would like to build their own MHE sensors for their 3dp.
You more than likely have all the parts needed, if you have junk computers around collecting dust.

Parts list:
1. An old cd rom or dvd rom
2. Cooling fan out of a computer power supply or case fan.

Take the rom completely apart, you will find a smooth rod for the laser movement, save it.
Take apart the laser itself, you will find two strong little magnets, save these and try not to break them, they are just glued in place.

Also save the slide motor and gear setup, you can use this to test your MHES with, won't need a battery or power supply, use this setup as a dc generator, turn the large gear with a drill or by hand, take a volt meter to determine which direction to turn the gear as to have a positive voltage off the red wire coming out of the gen motor, once you know this mark the direction on the gear then you will be ready to use this generator on the MHES circuit you build.

You will want to save the little LED on the front pc board.

Now to the fan, remove the sticker off the back of the fan, you will find a small rubber seal, remove it. Look into the hole you will see a center shaft with some kind of keeper on it, metal or plastic, remove it with a very small flat bladed screw driver, you will not need to save it.
Once removed, push the motor shaft out of the hole, the whole fan blade will come out. Look under the wire windings, you will see hopefully a three leaded-what looks kind of like a transistor, this is a hall effect sensor.
You will need to remove the windings along with the pc board they are mounted to, being careful not to damage the sensor. When this is complete unsolder the sensor also being careful so as not to over heat it. Some sensors will have four leads, I have not tried these, hopefully you will have aother fan to take apart.

Notate where the three leads were attached, the red wire of the fan motor goes to a diode then to one of the leads of the sensor, mark that lead in red, trace the black fan motor wire to another lead of the sensor, mark that lead in black,now you know posistive and negative of the sensor, the last lead is the output which should go high or have voltage when the south end of a magnet is posistioned in close proximity to it, within a couple of mm, depending on the strength of the magnet and voltage applied.

Now you are ready to build the ciruit, below is the schematic I used:

Should be very straight forward as to what components are needed, the resistor I used a 220 ohm, the hall effect sensor and the led you saved, you can find the polarity of the led using the gen, just turn it by hand needing no resistor.
With this knowledge you should be able to make a pcb solder all the components in place keeping in mind a way to mount the finished board and connecting it to the Ramps board or what ever project you have in mind to use it on, it will also work for endstops of a 3dp.

Now as for the rod and magnets you saved, here are some thingiverse prints they can be used for.

Enjoy, :D :D.


Re: DIY Magnetic Hall Effect Sensor, build one.
« Reply #1, on October 20th, 2014, 07:26 AM »
a word of cation, a lot of fan's have complete drivers in the " hall sensor" make sure you test it before you use it!

good stuff Jeff!


Jeff Nading

Re: DIY Magnetic Hall Effect Sensor, build one.
« Reply #2, on October 20th, 2014, 02:42 PM »Last edited on October 20th, 2014, 02:48 PM
Yes, that is what the generator is for, to test it. I think also, that is the difference between the three lead and the four leaded sensors, I tried two three lead sensors, they both worked. One would light the led when the magnet was applied the other would turn the led off when the magnet was applied, the led was on when not applied. Just need to find the correct one to use, I think the four lead sensors could be used as well, just use three of the four leads, but this would have to be tested.