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I am putting together a PiPhone but with slight mod to the power.

Is it possible to use powerboost 1000 charger to achieve the following?

  • power up rpi + pitft and the sim module,
  • recharge battery and/or power the devices directly when battery is low,
  • terminate power output to all devices via the switch on powerboost charger

The rest of the wiring is known, except how to wire powerboost charger to the sim module.

The sim module receives power and charge its battery via the 5v micro usb port. The jst on the powerboost charger receives 3.7v for the battery. What is the simplest way to allow the sim module to receive stable 5v power output from the powerboost jst?

Wiring reference: adafruit piPhone

My powerboost differs from this wiring link. I need to implement a switch on the power booster. Also I want to connect vio to the TFT 3v instead of to FONA Bat+ so I could do a data failover. prelim wiring attempt

Sean Lee
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2 Answers2

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Use the powerboost to power the pi only. Do not power the SIM and it's battery from the raspberry pi. (I'll explain how to wire it first, then I'll explain why...)

First-

  • wire the powerboost so that it's got a micro-USB on the 5v and Gnd (this will plug into and power the pi)
  • connect the +Bat and Gnd of the power boost to the +Bat and Gnd lines of the FONA
  • take your lipo (2500mAh-5000mAh) and plug that into the FONA JST-ph

You can plug your charger into either the powerboost or the FONA to recharge the battery(but not both at the same time).

The why-

  • there is a 'resettable' fuse between the USB and the 5V pin on the pi so it's not safe to power it from pin 2 or 4 on the GPIO
  • The fuse also makes it inadvisable to power the FONA from the pi, the FONA can draw between 20-500mA depending on what it's doing
  • You don't want to put the FONA after the Powerboost as it (and the pi) can draw more than the Powerboost can supply (during a voice call or GPRS data especially. see p. 60 of this- http://www.adafruit.com/datasheets/sim800h_hardware_design_v1.00.pdf)
  • The FONA powers itself directly from the Lipo battery anyway. The only thing it uses 5V for is to charge the battery. So if you use the battery to power it's own charger you are just generating heat ;-P

So the most reliable solution is use the FONA battery to power both devices. The powerboost only runs the pi which leaves you more power to do stuff with and there's less chance of popping the 'resettable' fuse, which takes hours to days to reset.

BTW - powering an Arduino as I describe I'm using around 100mAh. Most of that is the SIM800)

alphacharlie
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I would say that it should work.

Use the Powerboost 1000 battery charger to power the RPi and all things connected to the RPi. Notice that it just delivers 1000 mA and that all connected devices must not use more than 5 W.

The screen could be powered from the RPi 5 Voltage pin out (if that is within the specs for RPi), from the RPi 3.3 Voltage pin out (also see the RPi specs) or directly from the Powerboost 1000 Charger in parallel with the RPi.

The GSM SIM Module could be wired to a RPi and getting its power from the RPi:s 3.3 Voltage output, as per this link from Ada Fruit.

No, I have not tried this, but see no reasons why it shouldn't work, except that the marginals could be a bit slim with 1.0 A max output from the Powerbooster.

Anders
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