This is my first post on the forum, so apologies if I do something wrong.
I’m working on a new Smart Glasses project, and I’m wondering how I can power my setup. So far, my idea is to connect a 3.7V 800ma/H LiPo battery to a TP4056 board, to which the output of the TP405 is connect to a Mt3608 Boost Converter. The battery voltage would be boosted up to around 9V, which I can add to the VIN/RAW pin of the Arduino Nano or Pro Micro. I’ve seen others use Li-Ion batteries for portable projects, but those seem a bit heavy and bulky for a pair of glasses. I was also recommended to instead use two 3.7V batteries in series (2S I think) and connect it directly, but I’m not sure if I wold require another charging module. Would my setup work? (I’ve added an image that shows a very simple diagram of what I’m thinking).
As a bit of context, I’m planning to add a 128*32 I2C OLED Display, a HC-05 Bluetooth Module which would connect to my iOS phone, and maybe some other stuff like a cheap laser diode or a buzzer later, nothing that requires a lot of power. Even if my setup works, do you all have an estimate for how long I could power my project? I’m hoping a minimum of an hour. If my setup isn’t healthy for the battery or the board, please share any ideas that you might have.
From what I see from that fuzzy thing it is not wired correctly. Consider a schematic, it is much cleaner and easier to read. It would help a lot if you included links to each piece of hardware preferably containing technical details. How are you going to charge the battery? How much power does your design require? How long is the battery required to last
..etc???
Sorry, but you need to realise that the "Vin" pin of the Nano or Pro Mini is complete nonsense!
Once you have that sorted out, you need to consider that a Nano includes a USB chip that will only waste battery power, including when you put the mega328 to sleep. So you use a Pro Mini.
Now a Nano actually runs on 5 V. Well, if you ignore the USB chip as you should since it is completely useless for battery operation anyway, it will actually run on less but somewhere below 3.7 V, the processor will fail to run with the 16 MHz crystal. Similarly for the Pro Mini 5 V version which also has a 16 MHZ clock, but the 3.3 V Pro Mini with an 8 MHz clock will run perfectly on a 3.7 V battery (and much lower), it is just a little slower (like - half the speed ).
So that would be the proper choice for your LiPo rechargeable battery. Also your other devices such as the OLED will most likely also want to run on 3.7 V (because - that is exactly what they were designed to do as part of a mobile phone which always has that sort of battery ).
Thank you so much for your help! So if I choose a pro mini, where would I connect the 3.7v of the battery? Would I still use a boost converter to boost the voltage up to 5V and connect it to the 5V pin? Lastly (sorry for all the questions, I just don’t want to destroy anything), if you recommend me to power it through the 5V pin, will the voltage from the output of the boost converter remain steady even if the battery voltage decreases? Thank you so much!
geniusified:
So if I choose a pro mini, where would I connect the 3.7v of the battery?
To the "Vcc" pin. On a 3.3 V Pro Mini version (note that you can power it at 5 V for programming or indeed any other use, it is simply the same as the 5 V version but with an 8 MHz clock and a different regulator chip which you want to disable anyway) the "Vcc" pin is 3.3 V, not 5.
geniusified:
Would I still use a boost converter to boost the voltage up to 5V and connect it to the 5V pin?
No, since a boost converter simply wastes battery power unless you need 5 V for something that only works at 5 V. I think your other devices work at 3.3 V and presumably will tolerate 3.7 V.
geniusified:
Lastly, if you recommend me to power it through the 5V pin, will the voltage from the output of the boost converter remain steady even if the battery voltage decreases?
I don't recommend it as such but If a boost converter actually did fail to maintain regulation with battery voltage decrease to a safe level, throw it out! That is the critical part of its job.
I note some confusion here. The Pro Micro is completely different to a Nano or Pro Mini. I do not think it has a 3.3 V version but expect it would work just fine. I suspect however that referring to a Pro Micro was actually a typo?
The particular Oled you show is apparently discontinued however, according to Adafruit, it will run quite happily on 3v3
or 5v if you connect it in the correct fashion.
Paul__B:
Now a Nano actually runs on 5 V. Well, if you ignore the USB chip as you should since it is completely useless for battery operation anyway, it will actually run on less but somewhere below 3.7 V, the processor will fail to run with the 16 MHz crystal.
The Nano conveniently has an ISP header, so it's quite easy to set the fuses to use the internal 8 MHz oscillator. Of course it's far less accurate than a crystal but in many use cases, including timing-critical Serial communications, that doesn't matter.
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