While thinking about replacing the mini usb connector to a micro one on my G600 microscope , i've seen that post from Syonyk. Damn ! No real battery charging, straight to 5v. Warning : This is not an accurate analysis, it may contain errors or missing /misunderstood parts. Let's have a look. The partially reverse engineered/ contains error schematic /picture is as follows : The equivalent schematic is ( incomplete/may contain error ) : So indeed, VBUS (5v) is connected directly to VBAT through just a schottky (K14) and R12. On the other hand, the BMS circuit is tuned very low and will stop the charge at exactly 4.2 v. My battery is still healthy and only slightly puffy :) Let's use a real charging circuit and remove component so that VBUS is completely isolated from VBAT. Remove K14, the P-Mosfet (Q1) and R54 so that they are really isolated and there is no resistor between VBUS and ground (R54). I also removed a very small ...
I was always fascinated by the so call "transistor testers" that identify and report pin out, features of pretty much whatever you throw at it. They are based on Atmel 328p chip, the same as arduino nano. So why not do the same thing with a STM32/Bluepill ? The STM32 is faster, has a better ADC accuracy, more memory, can do float etc... and is not more expensive. Warning : I'm doing this for fun & to learn, it might contain error & plain misunderstanding So, i watched a couple of video on the general principle on how they work. This is not a "port" but a rewrite from ~ scratch. When something is weird, i check what the original one does for comparison. Measuring resistance So first thing first : Resistance & Capacitance. These 2 will unlock the other ones. So how do we measure resistance ? What we do is a resistor divider with a know resistance value: Measure = Vcc*(RtoTest/(RtoTest+Rknown)) As far as the ADC goes, it means ADC=...
I bought a few boost converters on ebay, they are based on MT3608, up to 30V, ~ 500 mA max which is fine for a lot of applications. Of course they are cheap. But they dont work, Vout~=Vin whatever the potentiometer says. Let's see why They do look like this : The variable resistor is "102" i.e. 1kOhm, the fixed resistor is 222= 2.2k The circuit works like this Vout 1k variable ==> FB 2.2k Gnd Vout is adjusted so that FB is 0.6V Let's write down the general equation for that circuit FB=0.6=Vout*(2.2k+alphaR)/(2.2l+R), with : * R the value of the variable resistor (1K) here * Alpha the coefficient of the variable resistor between 0 and 1 The module should be able to go up to 30V, with alpha=0 0.6=30*(2.2)/(2.2+R) => R=107 kOhm Ooops, the variable resistor is 1k (102) instead of 100k (104), it cannot work with the value Two options : Replace the variable resistor with the proper value i.e. 100kOhm Or hardwire t...
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