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I'm building a new schematic to set up an ESP8266 m-based motion detector which should only work during the night.

My goals are:

  • Use an RTC to store time and read time when ESP starts up (if not in time window, it will go back to sleep).
  • The ESP8266 will be coded to disable WiFi on boot to speed up the boot process, and to limit battery drain
  • The ESP8266 will only connect to WiFi when within the time window to send a signal to MQTT

I've made multiple schematics and PCBs already, but the trial-and-error is starting to cost a lost of money, so I'd like some experts to review of my schematic.

The schematics can be found here: https://we.tl/t-JaEAZL9Poa

In case some folks want to see the schematics directly, here they are:

Combined view of the schematic

For the expects amongst you, would you bother taking a quick look and based on your experience tell me if there are any major issues? Especially with focus on the latching circuit and the boot high/low interference I may occur when the ESP starts up that may compromise my complete schematic.

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    \$\begingroup\$ Stackexchange is designed for specific questions and answers. you can narrow down the question to your previous mistakes, join a forum and post your project there for general guidance, or pay an expert \$\endgroup\$
    – Anas Malas
    Commented Oct 16, 2022 at 9:28
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    \$\begingroup\$ Well, it's impossible to know from schematics if it works or not. The PDF looks more like a block diagram how to wire some modules together. \$\endgroup\$
    – Justme
    Commented Oct 16, 2022 at 10:00
  • \$\begingroup\$ buy a solderless breadboard for doing development work \$\endgroup\$
    – jsotola
    Commented Oct 16, 2022 at 19:01
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    \$\begingroup\$ there is absolutely no reason why anyone should have to download a file to understand your question ... see this electronics.stackexchange.com/questions/638651/… \$\endgroup\$
    – jsotola
    Commented Oct 16, 2022 at 19:03
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    \$\begingroup\$ "I've made multiple schema's and PCB's already, but the trial and error starts to cost a lost of money." What did your previous iterations look like (schematics)? What were the exact issues you had with them (scope plots would be a bonus)? Weren't you able to modify them, or at least gain knowledge for the next iteration? And most of all: it would better fit the nature of this Q&A site, if you'd split the issues into separate well defined questions. \$\endgroup\$
    – Velvet
    Commented Oct 17, 2022 at 14:38

2 Answers 2

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Here are a few design issues that I see.

  1. The VBAT isn't connect to anything other than to the 3.3V output of PowerU1 LDO. And as far as I can see, the LDO output isn't connect to VCC in any way, so your board isn't powered.
  2. Maximum operating voltage of ESP12-S is 3.6V, you seems to thinking of power the ESP12-S directly with VBAT. Not sure what type of battery you are using, but if you are thinking of power the ESP12-S with 3.7V LiPo battery, it will exceed the ESP12-S 3.6V maximum operating voltage, furthermore, when the battery is fully charge it could be as high as 4.2V.
  3. So VBAT should be connected via the input of the LDO instead of the output of the LDO, but you need to have protection diodes so that when VBAT and VIN both are trying to power the board, it won't damage the components.
  4. The MCP1700 LDO is a wrong part in meeting the peak current requirements of ESP12-S when WiFi is turn on, it will result in sudden voltage drop and reboot. Suggest to uses AP2112K or something equivalent.
  5. If you are using ESP12-S, the pull-up, pulldown resistors ESPR5-8 are not required as those has been built-in inside the ESP12-S module. For more detail, please refer to ESP12-S datasheet.
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  • \$\begingroup\$ This is wonderful feedback. Thank you soooo much ! \$\endgroup\$
    – Titi
    Commented Dec 27, 2022 at 8:26
  • \$\begingroup\$ I indeed have multiple different powers i'm playing with. I use a 1400mAh LiPo battery, with peak at 4.2V (BAT). That one I drop to 3.3V using my LDO with output VCC-IN. The VCC-IN powers my motion detector and is also the input power for my latching circuit. When motion is triggered, the latching circuit puts VCC out that powers the board. \$\endgroup\$
    – Titi
    Commented Dec 27, 2022 at 8:33
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So based on the feedback received, I've updated my schematic. I've also reconnected everything without nets to ensure I don't get those complaints anymore. It should make it more readable to those who wished connected nets. ;-)

Updated schematic

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