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Forum Index : Microcontroller and PC projects : Powering Duinomite Mega with Battery

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bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 11:52pm 22 May 2017
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Hi,

I tried powering the Duinomite Mega with a LiPo battery, but after couple of days of running I found the battery with a voltage of 1.48V.
I don't think this is very healthy for the battery and looking at the schematic of the Duinomite Mega I am not sure such under voltage protection is part of the design.
Maybe I should have enabled something?

Any ideas?

The schematic of the Duinomite Mega:
https://www.olimex.com/Products/Duino/Duinomite/DUINOMITE-MEGA/resources/DUINOMITE-MEGA-REV-C.pdf

Thanks in advance,
 
RonnS
Senior Member

Joined: 16/07/2015
Location: Germany
Posts: 120
Posted: 11:36am 23 May 2017
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I think there is no under voltage protection,You can observe the voltage and give an alarm at below 3.3V,Better you are using protected cells !!!
I myself use the battery only for buffering, the current consumption is too big for pure battery povering
 
bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 11:01pm 23 May 2017
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Thanks!
This is troubling.... I have to remove that battery ASAP.

I need the battery so I can make sure that duinomite has power approx 5 seconds after power outage so it can write to the SD card.

Can you provide a link to a battery with builtin non-destructive protection?

I am looking at replacing it with a 1F 5V capacitor like EECS5R5( )105 from Panasonic.
Spec sheet here:
https://www.electrokit.com/en/dlcapacitor-5-5v-1f-o19x5-5mm.47153


According to calculator here:
http://www.circuits.dk/calculator_capacitor_discharge.htm

I should be able to provide approx. 6 seconds of power from 4.2V to 3.0V.

What is the minimum voltage the SD card can be written? Is 3V enough?
 
twofingers
Guru

Joined: 02/06/2014
Location: Germany
Posts: 1141
Posted: 11:39pm 23 May 2017
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Hi Bobo,

did you read this(DuinoMite User's Manual p25:
  Quote  3.13. BATTERY

The DuinoMite and DuinoMite-Mega have a built-in LiPo battery charger and the hardware is designed to allow them to run in low power mode for battery operation.
USB-FAULT is connected to RG7 to allow the firmware to be aware that it is running on battery instead of an external power supply. If USB-FAULT is read as 0 the board is powered by battery. The battery charge state can be monitored by measuring the power supply on BAT port RB2. The Lithium Polimer battery is connected via the R31/R29 voltage divider (0.319727891) to RB2 port as RB2 can handle a maximum voltage of 3.3V but the battery voltage can go up to 4.2V when completely charged.

DM firmware adds PIN(21) analog input pin which could be used for Battery voltage monitoring. Note that voltage is sensed through voltage vivider as PIC32 inputs can't measure more than 3.3V while Li-Po battery voltage may go up to 4.2V when completely loaded. This is why the measured values from PIN(21) should be multiplied by the magic number 3.13 to get the real battery voltage.


I think it should be easy to use a MOSFET (or a relay) to cut off the BATT-power.

I don't know if Geoff made some changes in the later firmware releases.

Regards
Michael
 
RonnS
Senior Member

Joined: 16/07/2015
Location: Germany
Posts: 120
Posted: 12:17am 24 May 2017
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Please google for "Trustfire LIPO Battery with Protection PCB"
These lipos are available from 900 to 6000 ma, so you need then only a battery holder
and a Jst Connector


The latest mmbasicversion is V4.5 for the Duinomite, i believe
 
bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 12:20am 24 May 2017
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  twofingers said   Hi Bobo,

did you read this(DuinoMite User's Manual p25:
  Quote  3.13. BATTERY

The DuinoMite and DuinoMite-Mega have a built-in LiPo battery charger and the hardware is designed to allow them to run in low power mode for battery operation.
USB-FAULT is connected to RG7 to allow the firmware to be aware that it is running on battery instead of an external power supply. If USB-FAULT is read as 0 the board is powered by battery. The battery charge state can be monitored by measuring the power supply on BAT port RB2. The Lithium Polimer battery is connected via the R31/R29 voltage divider (0.319727891) to RB2 port as RB2 can handle a maximum voltage of 3.3V but the battery voltage can go up to 4.2V when completely charged.

DM firmware adds PIN(21) analog input pin which could be used for Battery voltage monitoring. Note that voltage is sensed through voltage vivider as PIC32 inputs can't measure more than 3.3V while Li-Po battery voltage may go up to 4.2V when completely loaded. This is why the measured values from PIN(21) should be multiplied by the magic number 3.13 to get the real battery voltage.


I think it should be easy to use a MOSFET (or a relay) to cut off the BATT-power.

I don't know if Geoff made some changes in the later firmware releases.

Regards
Michael


Thanks Michael,

I did read this.
I don't want to add more stuff to the already crowded (for my taste) solution. I think that a capacitor should do the job. I am just not sure what is the minimum voltage for writing to the SD card.
 
bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 12:27am 24 May 2017
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  RonnS said   Please google for "Trustfire LIPO Battery with Protection PCB"

All I am getting are batteries that protect for some time, and then enable a current draw, and then cycle between these statuses.

I think I will try with the capacitor.
 
twofingers
Guru

Joined: 02/06/2014
Location: Germany
Posts: 1141
Posted: 01:25am 24 May 2017
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  RonnS said   Please google for "Trustfire LIPO Battery with Protection PCB"

AFAIK the "Trustfire" batteries are fakes! I would never (again) buy them.
A better solution would be - IMHO - a brand name(Sony, Samsung, Panasonic ...) LiPo battery plus a ebay PCB.
 
MicroBlocks

Guru

Joined: 12/05/2012
Location: Thailand
Posts: 2209
Posted: 02:17am 24 May 2017
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I am surprised a 1F/5v super cap will only give you 6 seconds.
(What values did you use in the calculator)
What kind of power (mA) is needed?
Microblocks. Build with logic.
 
Geoffg

Guru

Joined: 06/06/2011
Location: Australia
Posts: 3167
Posted: 03:14am 24 May 2017
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Super caps have a high internal resistance so you can only get a milliamp or two out of them. Not enough to power the DuinoMite.

Geoff
Geoff Graham - http://geoffg.net
 
MicroBlocks

Guru

Joined: 12/05/2012
Location: Thailand
Posts: 2209
Posted: 04:27am 24 May 2017
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The one that Bobo2 posted has an internal resistance of 30 Ohm.
That should give about 160ma of current. and that would give about 12 seconds.

If the 160ma is not enough then use two. :)

A KEY application for supercaps is to provide interim power. So it should be the right solution. Just use enough capacity to suit your needs.

Edited by MicroBlocks 2017-05-25
Microblocks. Build with logic.
 
bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 10:34am 24 May 2017
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Thanks for all the advice!

I ordered the supercaps and will update with the result when they arrive.
 
Phil23
Guru

Joined: 27/03/2016
Location: Australia
Posts: 1664
Posted: 10:51am 24 May 2017
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Just wondering what the application is & where it's installed?

I've been looking at a couple of the solar spot lights in my garden, and assuming they have about 12 Watt hours of battery capacity (they are 100 Lumen ones).

If a solar solution would fit, one of these could be easily modified with a LM2596 module.

These particular lights were $35.00, and I'm guessing when they are on they could be drawing about 250mA.

Phil.

Opps,

Should have said Buck/Boost Reg.

Have the LM2596 on my mind as I'm thinking of converting one to run the aspiration fan on my weather station, which probably wants 2.0V.Edited by Phil23 2017-05-25
 
bigmik

Guru

Joined: 20/06/2011
Location: Australia
Posts: 2870
Posted: 11:48am 24 May 2017
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Hi BoBo2,

I think the simple answer is to use one of these

Xiaomi Battery Banks

To go in between your power input and the DuinoMite. Note that the Xiaomi brand is one of the few that can supply power and be charged at the same time.. Note also that there are many fakes out there and it is imperitive to buy from a legit source as the fakes can be dangerous with poor Chinese batteries..

Do a google search for the fakes so you can identify them.. I have bought from Banggood and they were legit units.. This one will supply 10Ahr which should power your DM for a day or so before you have any problems..

Kind Regards,

Mick
Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<
 
bobo2
Newbie

Joined: 26/10/2012
Location: Sweden
Posts: 36
Posted: 12:44am 01 Jun 2017
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Update:

So I got the supercap, but it does not really solve the problem.
The duinomite shuts down at about 1.5V, and to be able to write to the card on supercap power I need 3V. The charging time from 1.5V to 3V is almost 15 minutes... and this is too long if I am for example going for a short drive.
I may look in to smaller supercap (it would charge faster)... or maybe look at a solution with relay... or maybe try that battery pack Mick recommends.


I found some info on the minimum voltage for write here:
https://forum.arduino.cc/index.php?topic=51164.0
  Quote  Cards work over a range of voltages. The initialization voltage range is 2.0 to 3.6V. During initialization a very slow SPI clock is used to read the operation conditions register, OCR. This register gives the supported voltage range for operation. Most cards return 2.7 to 3.6V. Some cards can be configured to work as low as 1.8V.
 
paceman
Guru

Joined: 07/10/2011
Location: Australia
Posts: 1329
Posted: 01:45am 01 Jun 2017
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  bobo2 said   So I got the supercap, but it does not really solve the problem.
The duinomite shuts down at about 1.5V, and to be able to write to the card on supercap power I need 3V. ....
I may look in to smaller supercap (it would charge faster)... or maybe look at a solution with relay... or maybe try that battery pack Mick recommends.

In the Nov 2013 edition of Silicon Chip Geoff had a 'GPS Tracker' project that also needed this supply backup - I built one and it works fine. His power supply solution was probably appropriate to your needs. Link - GPS Tracker The 'Construction Pack' download available at the bottom of the link has the schematic, BOM and photos.

Greg
 
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