Inaccurate sensing with optical sensor.



  • I bought some optical sensors from Amazon, https://www.amazon.com/gp/product/B0719K9Z9R/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 After discussing with the seller if they would work with 3.3v. Of course, they don't appear to be working very well.

    I can trigger them with a piece of paper, but they're not detecting the filament very well. The light barely dims, and small movements make it fault and pause the print.

    I have tried adding a 10k resistor between the signal and the 3.3v in at the connector on the Duet.

    Should I look at replacing another resistor on the board? If so, would you be able to advise which one? I believe it may be R1 that's on the rear in the picture. But don't know how to be sure which one I need to replace.



  • This is described in the wiki, ends top sectioni. Best to replace 2 resistors



  • I understand that it says you should replace some resistors. I just can't figure out by looking at the board which resistor it should be. There are two on the back, labeled R1 & R2. Then there is one on the front that is closer to the plug. All have different writing on them.

    After doing some more digging. I think it's the R1 that is the 180ohm resistor, and should be replaced with 100 ohm, and R2 should be replaced with the 10k ohm resistor. It appears the resistor on the front is for the LED.


  • administrators

    The problem you are having isn't caused by lack of 3.3V compatibility, it's caused by the filament not blocking the infrared light sufficiently. You need to use an opto switch with small IR elements, and you need to set the height of the filament in the slot to line up the filament precisely with the IR elements - then hold it at that height, for example by guiding it with two pieces of Capricorn PTFE tubing, one on each side of the slot.



  • Any recommendations on some with small IR elements? I had a hard enough time deciding to get these.

    I can re-print a mount that can hold the filament more centered. I'll let you know if that helps.


 

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