Magnetic Linear Encoder - pcb/kit

[willo]

Makerbot has a nice, simple linear encoder solution, but it's $50/unit/axis! Check it out here:
http://wiki.makerbot.com/mle

Note that the magnet is just magnetic tape. This solution can scale to whatever size Shapeoko you've built for a few dollars. This is really nice for us.

I'm considering having a batch of boards made for people who aren't afraid of the soldering iron. If interest is low, I'll just use batchpcb.
If I can get commits for enough boards, I'll have an entire panel made.

I think I can kit these up for under $20 with PCB and encoder chip. I suppose I'm willing to build them (one time only offer to get enough interest) for an extra $10/board. (I have hand reflow gear and a microscope) I'm putting the cost ceiling at $20 per kit and $30 built (plus shipping). I will reduce the price depending on actual parts costs at order time. I'm not sold on the connector/cable they use, so expect that to change to a normal header.

Alternatively, you can just buy a board and populate it yourself. I estimate the board cost to be under $10/unit. I plan to alter the board layout to fit certain handy Shapeoko mounting holes. I'll post the layout here for review. Please indicate your interest with quantity(X) and description below:

X - PCB
X - PCB/kit diy soldering (all parts in a baggie ready for you build)
X - PCB/kit presoldered (all SMD parts mounted) Header will be loose for you to attach as you prefer.

I will handle payments via paypal. I'm not taking money at this time.

[ejs]

I love the idea of an encoder. However, my concern with this is Arduino-centric, only because of being GRBL-centric. The linked page shows the breakout requiring pins 2 and 3. The only reason that would need to be the case is because those pins allow for external interrupts. They are the only two so-configured, meaning from a 328 chip standpoint, only one axis could be coded.

This would be fun to play with as a concept--consider me more interested than not--but that's a pretty restrictive implementation limitation. Anyone's thoughts on where this could be fit in a non-duino context would be great to hear.

[willo]

Hmm. I really doubt that interrupts are required on this.
However, you can enable more. See http://www.arduino.cc/playground/Code/Interrupts
You can enable just about all pins. I'm more than happy to burn an arduino for encoders...

[forgottenCNC]

Ejs is correct about there being only 2 external interrupts on the Arduino UNO 328 chip set (its not a coding limitation - its a limitation of the chip) and the reason interrupts are used in the example is because you don't what to miss a change in state as you are basically “counting” gray code to determine a position.

In saying this you may not need to use interrupts if the change in gray code for the encoder dose not exceed the total tickcount for the GRBL. So you will need to do the maths for Movement Vs Tickcount

http://arduino.cc/en/Main/ArduinoBoardUno

http://www.atmel.com/Images/doc8161.pdf


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[hugov]

Note that the magnet is just magnetic tape. This solution can scale to whatever size Shapeoko you've built for a few dollars. This is really nice for us.

I had a look at this IC and think you're mistaken about the tape: it's not "just" magnetic tape, it's special tape that has alternative N-S poles at carefully controlled spacings. I had a quick look but couldn't find any suitable tape. If you can supply the tape, I'm definitely interested to buy some of these.

[bemarkt]

Hi! I would like to share this great online resource for anyone seeking a linear-encoder: http://www.directindustry.com/industria ... 65005.html. Hope this is a useful resource for you other readers.

[WillAdams]

The above message is probably spam, but I'm inclined to let it stand since it's on-topic. Anyone else interested in linear encoders and want to research a bit for the wiki? (so as to balance out the current commercial bias?)