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  • Author Author: alexandru.cohal
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Smart Exhibit: Blog #4: Electronic schematic, system building and sanity checks

alexandru.cohal

Hello!

 

As explained in my previous blog post ( Smart Exhibit: Blog #3: The hardware components ), I need some extra components (temperature, humidity, light, sound and motion sensors, speaker, push-button, battery and battery charger) for my project, Smart Exhibit. Last week I received these components together with the Arduino Nano 33 IoT board image So, I started playing with them and this is the summary of what I did:

  • I tested the functionality of all these components together with the Arduino Nano 33 IoT board
  • I designed the electronic schematic of my system using Fritzing. I pushed this schematic to my repository (https://github.com/alexandru-cohal/SmartExhibit). Below you can see it.


image

  • I implemented for each component a Sanity Check short program. I know from my previous projects that it is always useful to have such programs for testing different functionalities with each component in particular and also to verify that the respective component is actually working fine (for the moments when I am in doubt that something might have happened with the component or with the connection between the component and the board image)
  • I connected all the components and the Arduino board together using a breadboard (I spent some time with my obsession of very clean and neat wirings but in the end it worth the effort image). Below you can see some photos of how the system looks. Pretty good, right? imageimage

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  • I implemented a Sanity Check program for the whole system (the Arduino board + all the components). Again, this is for checking that all the components are working when connected together with the board at the same time and all the connections are fine (Rule number 1: There are never enough tests and checks image)
  • I pushed all the Sanity Checks programs to my repository (https://github.com/alexandru-cohal/SmartExhibit)
  • I kept my Trello board updated (https://trello.com/b/qwcDuQMy/smartexhibit).

 

I had a lot of fun playing with all the components and the Arduino Nano 33 IoT board but I am pretty sure that this is only the beginning image

  • in reply to makervanlabs

    Thank you image I will tell you the secret of how I managed to make the breadboard to look like this image I used the wires from a general breadboard jumper wire set (like this one, for example) but I cut them in order to be the perfect length and to stay parallel with the breadboard image

     

    I used the DHT11 temperature and humidity sensor which comes into a module with built-in filtering capacitor and pull-up resistor. So I didn't choose the values for the capacitor and resistor, they were already set image. I know that the pull-up resistors in the Arduino based projects should be around 10kΩ based on the general ranges of the current and voltage values but, to be honest, I never actually checked and calculated this. On this page I found a nice discussion about the range of values for the pull-up resistor.

  • That breadboard really does look very neat   . I should seriously start working on my breadboard technique (which would benefit from buying proper wire as a start).

     

    Out of curiosity: I normally see a 10kΩ pullup on the DHT11's data line, any particular reason you went with less than that?

  • in reply to javagoza

    Hi!

     

    I was also a bit skeptical in the beginning if this will work or not. But until now, based on the tests I did, I didn't notice any problems (e.g. slowness, glitchy analogue pins) when I power the Arduino Nano 33 IoT board with a LiPo 3.7V battery.

     

    Though, the battery's nominal voltage is 3.7 V, but when it is fully charged it reaches 4.2 V. Based on the MPM3610's datasheet, the range between 4.5V and 21V is the recommended input, so I guess it is not a strict limitation but a limitation for guaranteeing the functionality. These 2 aspects also count.

     

    I will do more tests with the whole range of the battery's voltage and I will see if I will notice some problems. I will also write here what will be the results image

  • Hi,

    I am curious. You're powering the board with only 3.7 volts. The MPM3610 Step Down Converter specifications indicate an input range between 4.5V and 21V. Have you noticed any problems in your tests?

     

    image

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    Arduino nano 33 IoT Schematics:

     

    https://content.arduino.cc/assets/NANO33IoTV2.0_sch.pdf

     

    MPM3610 Step Down Converter Datasheet

     

    https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MPM3…