Smart Effector's White LEDs suddenly gone dim?



  • I've just finished putting together my latest and first truly custom build (I built a precision delta based on dc42's blog posts and BoM - a story for another post!).

    I'm in the process of getting to know it and fine tuning my prints. Throughout this process, the 3 white LEDs were always nice and bright like this:

    0_1551224201808_20190224_232027.jpg
    This picture was taken in a near dark room. The reflections in the mirror are the 2 nearest LEDs from on the effector.

    Then, yesterday, while in the middle of printing, all of a sudden the LEDs went dim. This is how it now looks in a dark room.
    0_1551224743256_20190226_234452.jpg
    Perhaps it's hard to tell from the image if my phone is compensating for the low light, but believe me it is substantially dimmer. I've tried wiggling my connections and resetting the printer etc. but it seems to make no difference. Note that the LEDs aren't flickering bright and dim - they went dim and stayed dim.

    Of course, I am quite happy to accept this new brightness. I just want to be sure it isn't the first sign of some greater electrical problem I should be aware of etc.? As far as I can tell, it hasn't affected the effector in the slightest. The hotend still gets hot, the thermistor is still reporting an accurate temperature and the Z probe works. The heater LED seems to be the same as it always was. As I type now it is happily printing away.

    My last detail is that I'm running the printer with a 24v PSU. However, my print cooling fan is 12v. I have used the jumper on the appropriate pins. I didn't think this was the cause of the problem since immediately after changing the fan the brightness of the LEDs was the same as normal. The dimming happened mid-print.

    Is this supposed to/known to happen for any reason?
    Thanks!

    Edit: Reading around a bit more, I have a feeling I may have misunderstood something around using a 12v fan with a 24v PSU and fitting the jumper... perhaps someone could confirm?


  • administrators

    The jumper must be fitted if the supply to the heatsink fan is 12V. What voltage is your heatsink fan? Is the heatsink fan running at normal speed?

    The LEDs are driven through a 604 ohm and 140 ohm resistor in series. The jumper bypasses the 604 ohm resistor.



  • Ahh I see. That's where I misinterpreted and messed up then! I thought that if I wanted to use a 12v fan I could put the jumper on and it would have the effect of stepping down the voltage... Clearly I didn't think it through...!

    I've essentially powered the LEDs and 12v fan with 24v and without the 604ohm resistor then, correct? I assume the damage to the LEDs is therefore irreversible?

    I'm now ordering a buck converter so I can reattach the 12v fan...


  • administrators

    If the LEDs still light up then they have probably not been seriously damaged. It's much more likely that the 140 ohm resistor has partially burned out.



  • Understood, thanks! They do still seem to light up. I will look into replacing the resistor if possible at another time. Thank you!


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