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Forum Index : Microcontroller and PC projects : PicoMite: getting 5V from 3.7V (VSYS)
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Hi folks, I need to temporarily tack a 5V GPS unit onto my 3.7V powered Pico Handheld - don't ask, it would just be less work than building something specific for a short-lived project. Can I just take the ~3.7V from the Pico VSYS through one of these: https://www.aliexpress.com/item/1005004010491015.html Will the circuit need any additional protection ? There is already a 1N5818 between the battery and VSYS. Thanks in advance, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3152 |
And then regulate down from 12V to 5V? This might do a better job for you (with the emphasis on "might") if 500mA is enough: Aliex: Boost to 5V PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4253 |
Yes, that will work. Adjust to 5v before connecting gps. Most gps will work from 3.7v though. Internally they run on 3.3 or 2.5v Edited 2023-04-30 03:32 by Volhout PicomiteVGA PETSCII ROBOTS |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Huh? It's configurable, it does 5V, 8V, 9V or 12V. Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3152 |
Ah, sorry--I didn't scroll down to see the solder-blob connections on the back which select output voltage. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Thanks, so I should probably just try powering it directly from VSYS and see what, if any, life there is. Tom Edited 2023-04-30 04:00 by thwill Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6805 |
Looks like it should be fine, Tom. Handy (and cheap!) little board. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1611 |
If there is no life (as we know it) can you simply use a 1.2 volt rechargeable cell connected on top of the 3.7 volt supply? Or maybe 1.5 volt AA cell with an ordinary diode in series with the +ve (use a 10k resistor to zero volts to see the final output voltage in that case). Bill Keep safe. Live long and prosper. |
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Quazee137 Guru Joined: 07/08/2016 Location: United StatesPosts: 573 |
I know it works in PIC's not sure the RP2040. Use PWM to drive a boost circuit. A lot of the programmers did that even made negative for old Eproms. Quazee137 Edited 2023-04-30 15:32 by Quazee137 |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1611 |
I've done that with 555s as well using a voltage doubler but I doubt the the RP2040 could provide the power for the GPS without some sort of buffer. Bill Keep safe. Live long and prosper. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6805 |
A diode pump fed from a PWM pin will get 5V (or even -5V!) easily, but with the low current available from the RP2040 there will be very little current available. Probably only a couple of mA. Put a paralleled up hex inverter chip in as a buffer and it may be fine. However, the PCBs thhat Tom has found work out *way* cheaper and smaller than a cobbled together system and will very likely "just work" (at the expense of some SMPS hash noise). :) 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: 4047 |
Thanks folks, it looks like the GPS is somewhat functional at 3.3V, but it takes much longer to get an initial lock. If that doesn't work out then I already have ten of those modules from an earlier AliExpress spending spree where I came across then in passing and thought they sounded useful. Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1611 |
You may need level shifters in that case? Bill Keep safe. Live long and prosper. |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4253 |
Typically GPS modules are power hungry. 40mA is not strange. Try your phone, disable location, and you get 10-20% more time from the battery. Pumpin from even a hex inverter is inadequate. Toms prposal is the best, unless 3.7V from the battery is sufficient for this particular module. 3.7v not 3.3v.... Edited 2023-04-30 18:10 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6805 |
I've never used a GPS module - and the one in my phone got switched off when I first got it. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Quazee137 Guru Joined: 07/08/2016 Location: United StatesPosts: 573 |
I am using a boost but its from 5 to 24. The chip has an enable pin so its easy to turn on/off. See if the GPS has a enable pin to turn it on/off else add a transistor. Quazee137 |
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