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Forum Index : Microcontroller and PC projects : PicoMite: powering by battery
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Hi folks, I've read (and not necessarily completely understood) what the PicoMite manual has to say on the matter (p10) and I was hoping to get more insight from TBS before risking the magic smoke. I want to run a PicoMite (@252 or 378MHz) + 2.8" ILI9341 SPI Display + 4021 shift register + 1 or 1.5W 8R speaker. Initially I'd like to run off 3xAAA batteries (because that's the holder I've got - well I've also got 4xAA but 6+V is too much isn't it?) but eventually I want a small(ish) LiPo and charging circuit. Now do I just connect this to VBUS, or is it something more complicated ? Any considerations regarding whether the USB is also connected at the same time ? What ballpark runtime can I expect ? Best wishes, Tom Edited 2022-12-07 02:22 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
Connect your battery to VSYS via a schottky diode. Do not connect to VBUS if you are also connecting USB - BAD!!! Edited 2022-12-07 03:20 by matherp |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5089 |
Without knowing details: AA batteries are between 1Ah and 2Ah. For 4.5v you consume 50mA pico 50mA backlight and LCD Assume 100mA audio (450mW music power) That is quite loud! That is 200mA The cheap battery will last 5h, the expensive 10 hours. Volhout Do not run 6v, the pico will die. PicomiteVGA PETSCII ROBOTS |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Ok, thanks guys. Currently the display is tapping its power from VSYS (as per @Mixtel90's PicoMite backpack schematic which I am shamelessly ripping off), is this still going to work when fed with 4.5V (or 3.7V for Lithium) ? Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| darthvader Regular Member  Joined: 31/01/2020 Location: FrancePosts: 87 |
For costly AA replacement i use this one  li ion 1.5v usb cheers. Theory is when we know everything but nothing work ... Practice is when everything work but no one know why ;) |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5089 |
Hi Tom, The pico is designed to also work with 3.7V Lithium batteries. Most displays have their own regulator and should work fine from Litium batteries. The game pad must be run from 3.3V. The backlight of the LCD may be the only problem. I can not predict , so you will have to try. Some white LED's need around 4V, some need only 2 or 3v. Not sure what is in your LCD display. Anyway, if you connect the backlight to the 3.7V lithium battery you will see if it lights or not (use a resistor of 33ohm in series, just to be sure). Most likely it will be more dim than on 5V, but it may just be okay. The audio amplifier (1.5 watt is most likely class D) will just work fine from 3.7V. Do not power it from 3.3V, since it uses more power than the pico on board 3.3V can supply. Volhout Edited 2022-12-07 04:14 by Volhout PicomiteVGA PETSCII ROBOTS |
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| steview_de Newbie  Joined: 02/11/2022 Location: GermanyPosts: 12 |
Hi Tom, according to "external" / independent power supply, i would allways prefer 3.7V Li Ion batteries. You can get them as 18650 cells with 3Ah. And look at the size ... i don't know your project, but i think there must be enough space. There are also interesting solutions to charge them via usb. "Stevie" click EDIT: Look at the timestamp of the posts of Volhout and me;-) Edited 2022-12-07 04:16 by steview_de |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
If you believe the Chinese you can get 18650s up to any mythical Ah rating you like. :) Some will even give 3.7V for a while... Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Hi Volhout, It's just a speaker that says it is 1.5W, there is no amp ... yet. Apologies for not advertising exactly what I am building, though I suspect some of you have guessed given my interests and the parts list, but I want a chance to do it myself (all be it with a lot of help on the individual modules) rather than have it designed (and critiqued) by committee. When I publish the schematic then you can consider "hunting season open"  .Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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karlelch Senior Member  Joined: 30/10/2014 Location: GermanyPosts: 237 |
In the Pico documentation (Raspberry Pi Pico Datasheet) in Chapter "4.5. Powering Pico", the different options of powering a Pico are nicely described. There are options that describe how connect battery and USB safely (in parallel, if needed). |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2566 |
These are cheap. 1A and 2A usb out. Mini usb to charge and a lcd battery level  |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
You could just use a phone power bank to supply 5 volts. An an auto power off circuit would be handy too. A Picaxe music box I made for the grand kids lasted for years, where ever it is now it's probably a corroded mess inside. Bill Keep safe. Live long and prosper. |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Think I might grab some of these  Craig |
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twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1593 |
deleted Edited 2022-12-07 20:21 by twofingers causality ≠correlation ≠coincidence |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
A bit big ;-) The ideal sized power supply would be ~2.5Ah and no bigger than 4.5mm x 80mm x 50mm - is such a capacity possible ? I guess that would be ideal, but it would also be "gold plating" rather than strictly necessary. Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
See this listing and pick what suits |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Many thanks Peter, it appears that exactly the cell I want exists 405080 .Now charging circutry, I've got some O3962A modules (looks like this https://www.aliexpress.com/i/32963400277.html) that I can hopefully scavenge from some of @lew247's defunct weather station PCBs - they look suitable to me, but what do I know ? Best wishes, Tom Edited 2022-12-07 21:37 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
An auto power circuit Not if kids are going to use your device. In my experience they are very good at turning things on, lights, chargers, ipads and the like but turning them off or unplugging the charger? It's a foreign concept to them. Bill Keep safe. Live long and prosper. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Hi folks, My first ever LiPo has been delivered and has come randomly (?) with a through-hole BC547, it's obviously deliberate (it is even in its own tiny baggy). Can anyone tell me what that is about ? Also, is there anyone who could find time to comment on this: Best wishes, Tom Edited 2022-12-13 00:35 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
I observe that half of this 03962A unit appears to be "protection circuitry", that seems to be duplicated (even looks like the same pair of ICs) in a sliver of PCB that is already attached to the LiPo, is that going to be a problem? Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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