TERES-I update. First feedback from our customers


magnet

Today we shipped all pending orders for TERES-I and we start to get valuable feedback from our customers!

First thing – we missed the magnet assembly in the instruction manual (blush). This leaded to laptops not go in suspend mode when lit is closed.

We updated this in the assembly manual 1.1 which is now on the web and included in the GitHub too in sources so people who notice typos and want to help improveing the Bulgarian-English language in which the manual is written.

Another issue reported immediately which we missed during our testing is that on small percentage of the laptops the LCD backlight step-up inductor cause annoying sound when LCD backlight is with 50% brightness.

BUZ

It’s a interesting phenomenia as the backlight PWM is 300Hz which is not possible to hear, but when LCD backlight is switch ON and OFF high current surges are happening and some harmonics cause mechanical resonance with this inductor.

The solutions may be few:

  • play with PWM frequency to get away from this frequency which cause the mechanical resonance – pure software approach which need lot of experimenting
  • adding small double adhesive matt on top of the inductor which make contact with the back plastic and this way absorb all vibrations – we start to add this mat as soon as we discover this issue to all laptops no matter if they buzz or not. Not very aestetish but quick and dirty solution:

ABS.jpg

  • Add more capacitors to the PWM power supply which to handle this current surge, adding 100 uF seems to remove the problem, but the first lot was already assembled and many laptops are already shipped – so this we will implement in the second assembly.

 

We have two reports about problems caused by the touch pad after “apt-get update / upgrade” we have to look more closely into this issue. For the moment we do not recommend you to update and upgrade your Ubuntu packages or if you do this and something stop working to revert to the original image – this is pretty easy just download the image write it to SD card, boot and run the eMMC copy script.

6 Comments (+add yours?)

  1. Riccio
    Nov 04, 2017 @ 01:58:01

    Regarding the audible range, 300Hz is heard: https://en.wikipedia.org/wiki/Hearing_range#Humans

    Reply

  2. Ged
    Nov 05, 2017 @ 02:44:27

    PWMed backlight is not very eye-friendly and should not have been used in the first place. Please consider a constant-current solution for future designs!

    Reply

    • Anton Zinoviev
      Nov 05, 2017 @ 12:14:49

      An alternative would be to use a higher frequency, 1.5kHz should be ok. I think that 300Hz (the frequency used by Teres 1) is above the average of the current laptops. At this frequency nobody (even the sensitive people) will be able to observe the flickering of the display. The effect, however, will be felt, especially with moving images. For example when the mouse cursor moves, our brain will not be able to predict properly its direction and expected position, or for some miliseconds will see many cursors. To some people such effect causes disorientation and headache, but most people won’t even realise the effect exists. They will perceive it as something normal and will be unaware of the slight fatigue it causes.

      Reply

  3. Trackback: TERES-I update. First feedback from our customers https://olimex.wo… | Dr. Roy Schestowitz (罗伊)
  4. Nicolas
    Nov 15, 2017 @ 18:08:10

    What would the easiest way to get a non-US (specifically Danish) keyboard on the TERES be?

    Reply

  5. Andrew Bernard
    Nov 16, 2017 @ 05:40:30

    I’m very much looking forward to ordering one of these shortly. In the meantime, I will revise and correct the manual, putting it into proper English for you (no disrespect intended). Happy to help!

    Reply

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