# cheap electronic compass

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#### oem_odm

##### New Member

hi everyone

please see the image below in reference to a cheap compass. I'm not an electronic engineer so pls bear in mind

the idea is to create cheapest form of electronic compass. it will be in-accurate by about 15degrees, slower than gyro ones, and need to be held flat like a compass. Whats wanted is cheap + general direction according to 8 co-ordinates.

just like with normal compass, its bar rotates on a pin. the bar is fixed to a black card (thin, light, black about 200gr/gsm card). A slot in the card to allow IR light to pass through for the photo interuptors. depending on the cards rotated position, 1 or 2 photo interupters would be postive (passing IR light through the slot. With each photo interupter connected to an MCU pin each, could calculate the position......

right?

#### Menticol

##### Active Member
Awesome draeing, are you a designer?

#### birdman0_o

##### Active Member
Ya, what software made that drawing?

#### oem_odm

##### New Member
funny, not quite the feedback i was looking for chaps. it's solidworks + touch of photoshop.

Any feedback on the actual post would be very cool

#### blueroomelectronics

##### Well-Known Member
Electronic compasses are not very expensive for low resolution models, are you planning to mass produce your design? What would be the need for a low resolution compass? What product(s) do you envision could use it?

#### oem_odm

##### New Member
hi blueroom

could you recommend some cheap electronic compasses and sources? - similiar to what I've envisaged.

(mass production is in mind - a robot application)

thanks

#### blueroomelectronics

##### Well-Known Member
Try digikey search for compass, in quantity these are cheap.

#### oem_odm

##### New Member
i see your point. the card will have holes round its edge. those holes depending on the position of the needle will allow/block the optical sensors.

#### Jirka46

##### New Member
i see your point. the card will have holes round its edge. those holes depending on the position of the needle will allow/block the optical sensors.

If you used Grey code wheel printed on the bottom of your card and reflective sensors, you would get 16 positions with just four sensors and each additional sensor would double number of them. Also it would be easier and cheaper to make than cutting holes or slot.

Jirka

See this
Optical Encoder Wheel Generator

#### Vizier87

##### Active Member
try KMZ51 / KMZ52 as well. They're also cheap.

#### oem_odm

##### New Member
If you used Grey code wheel printed on the bottom of your card and reflective sensors, you would get 16 positions with just four sensors and each additional sensor would double number of them. Also it would be easier and cheaper to make than cutting holes or slot.

Jirka

See this
Optical Encoder Wheel Generator

hi jirka, great reply thanks....would you mind doing me a drawing of some sort so i could understand you better? (think your idea is great)

#### oem_odm

##### New Member
try KMZ51 / KMZ52 as well. They're also cheap.

hi Vizier87 - how cheap are these?

#### Jirka46

##### New Member
hi jirka, great reply thanks....would you mind doing me a drawing of some sort so i could understand you better? (think your idea is great)

Hi, the picture shows what I meant. The encoding disc would be printed on paper and glued to the bottom of blue disk. Four sensors would read it. You would have to decode grey code to binary in your MCU.
Jirka

#### Attachments

• COMPASS.jpg
30.8 KB · Views: 368

#### oem_odm

##### New Member
Hi Jirka,

Yes i see your idea. It's good. You mount all the sensors on the same tangent line.

#### oem_odm

##### New Member
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