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added textual howto mod 'pearl' coils

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then 2020-10-30 22:16:19 +01:00
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electronics/README.md
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@ -11,4 +11,24 @@
* PCB: Send the gerbers from this repo to your fab of choice.
* ESP12F: Widely available.
* AM1117 3.3v Regulator: Widely available.
* QI compatible wireless charging coil delivering 5v and > [500 mA](https://docs.ai-thinker.com/_media/esp8266/docs/esp-12f_product_specification_en.pdf): For example [this](https://nl.aliexpress.com/item/4001154059743.html), search keywords: "pcba receiver module qi".
* QI compatible wireless charging coil delivering 5v and > [500 mA](https://docs.ai-thinker.com/_media/esp8266/docs/esp-12f_product_specification_en.pdf): For example [this](https://aliexpress.com/item/4001154059743.html), search keywords: "pcba receiver module qi". Alternatively you could repurpose coils advertised to convert non-QI phones to wireless charging, such as [these](https://www.pearl.de/mtrkw-9811-qi-kompatible-receiver-pads.shtml)*.
* **NOTE**: Be aware that these 'converter pads' could contain additional circuitry that condition the output for use with specific mobile phones (the pearl.de ones do). Below is a guide to modify the 'pearl' coils to deliver maximum voltage (5v)constantly, instead of switching to low power, 2.5v output when not enough/too much current is drawn.
### Modding Coils/pads
If you have soldered all components together and your ESP12f won't boot, you might have to modifiy your charging coil+circuit a bit. To make sure it's the coild, measure the output of the coils electronics on the + and - (gnd) terminals. If your multimeter reads ~2.5 volts you need to modify the circuit. (Disclaimer: the exact details on how this circuit works are yet unclear, comparing to a working coil revealed several differences in the electronics, matching them up made the non working coil output the needed 5v).
#### Step 1
Take off the follwing chips indicated by the following silkscreen codes:
* Q3 (chip markings: p7)
* Q4 (chip markings: wsc7)
A hot air reworking station + tweezers will take quick care that (settings: 1 second on 320deg, modertate airflow). Withouth hotair you could try a soldering iron or fine wirecutters to simply cut away the chips. The flexible PCB is very fragile tho.
##### Step 2
With both chips removed, you have to bridge two of the three (now) bare connections of the transitor Q4. I could not find a datasheet on this transitor so please refer to the photo's to see which pins.