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Topic: Obtain a stable 5V output (Read 1 time) previous topic - next topic

sturla_78

Hello to everybody,
i would recover a gsm module that work with 5V power and logic and use with my mkr1000. My problem is how obtain a stable 5V for power and communicate correctly with mkr1000 in both situation when mkr is powered from usb and battery (for example for determine a blackout in house).

I have read the datasheet, if i not wrong, the 5V pin has an output to 5 volt only when connected to usb, in this way i cannot use a llc for my project.

There is a solution for this problem?

Thanks for help

ballscrewbob

Most GSM modules have a minimum or maximum volatge.
They can vary slightly but you didnt give any information so it is impossible to give a real answer.

Also you could feed the module from a slightly different feed by splitting a supply so that you know the GSM module is getting what it needs and feeding the remainder to the USB port.
Dont forget a common ground if you take that approach.

It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

sturla_78

Thanks for reply ballscrewbob,
The gsm module is adafruit https://www.adafruit.com/product/1963, my goal is power directly from mkr100 using the 5V input of the module so i have only the input usb connected to mkr (both module have a backup battery connected).
My scope is to send an sms when there is a blackout in house.
But during blackout the 5V pin of mkr change voltage from 5V to 3.7V (if i have understood correctly the specifics).

Sorry but i have no idea on how produce a constant 5V

Thanks again

ballscrewbob

#3
Aug 27, 2018, 02:01 pm Last Edit: Aug 27, 2018, 02:02 pm by ballscrewbob
Thats better. The extra info means so much more to me now.



That circuit when fed to a voltage divider would allow you to sense when power to the USB port is lost (house power) dont forget that your voltage divider needs to be calculated to the 3.3 volt range to suit the MKR.

You would only need to splice into the power and ground cables and NOT the DATA lines.


It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

sturla_78

Thanks, great idea  :)

I try to use this method for power the GSM module.

According to your opinion, can i use the same usb power cable for power both mkr and GMS ?

Thanks.

ballscrewbob

Yes so long as both items together do not exceed the current capacity of the supply you should be just fine.
It would simply be a matter of two extra wires from that shown above just to supply the GSM too.

Most USB power supplies have a limit of around 500mA so whatever it says on your PSU is your limit.
It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

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