LattePanda ALPHA DC Power insights

userHead anonymous 2018-12-29 13:16:19 54812 Views27 Replies
This is a continuation of my previous thread (DC Power Experiment...)

Supplementary info:
Power (PWR) LED is blue-colored
D13 LED (appears to be coming from Arduino Leonardo's D13 output) is red-colored.

When DC supply power is low, none of the PWR or D13 LED would lit.
When I played with the DC power and gradually increased the voltage level, first thing to notice is Blue LED started to blink at a low frequency (about one short blink every 3 second or so.) the Red LED stay unlit or extremely vary faint/barely noticeable.

I further increased the DC supply voltage, the Red LED started initially very faint, pretty useless at this point. (No change on Blue LED blinking frequency.)
When DC voltage increased high enough, the Red LED started to fast blink for about 5 second or so.) After that, the Red LED stayed constantly lit. (Blue LED is still in its slow-blink pattern.)

One might notice the Red LED is still quite dim, increase the DC supply voltage to make sure the Red LED is in its normal brightness (about the same level as the Blue LED when it lit.)

ONLY at this point, the system is ready to be powered up.

Press the POWER button for about 8 seconds or so, until you see both the Blue and Red LEDs stayed ON all the time (No more blinking.)
At this time, if you see both LEDs stayed ON and no interruption, the DC power side of the necessary condition is (almost) met. If you see other issues (e.g., no Display, etc.) that's a different level of problems.
** Why I said "almost"? It's because power supply stability (lack of big capacitor, USB wire gauge/length, etc.), the operation condition sits in marginal satisfactory region. I will at least increase the DC voltage by 0.7V on the safe side.

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