From 4d9c837e4c96d64724f1a2666ab1b620d0e39a0e Mon Sep 17 00:00:00 2001 From: Bdale Garbee Date: Wed, 30 May 2018 08:23:54 -0600 Subject: [PATCH] document what's required to make the 12V switcher on v2.0 work --- Notebook | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) create mode 100644 Notebook diff --git a/Notebook b/Notebook new file mode 100644 index 0000000..a831435 --- /dev/null +++ b/Notebook @@ -0,0 +1,17 @@ +2018.05.30 + +To make v2.0 useful: + +Replace the 27k in the lower leg of the AP3012 comparator circuit with a 56k +to drop the voltage from ~27V to just under 12V. + +In the AP3012 circuit, rotate the inductor and 4.7uF caps 90 degrees, and lift +pin 5 of the IC, to detach all of them from the 3.3V rail. Use a wire to +connect all of them to pin 4, the gpio driving the circuit. + +The net effect is that we're making 12V from the gpio, which means all the LED +current and switcher inefficiency is coming as current through that gpio. The +measured LED current is around 7mA, so this is "safe" for the SOC, but really +not a great plan... + +Need to redesign this in the future to use a transistor/FET switch. -- 2.30.2