OLIMEXINO-328 Battery

[Kurt]

How much voltage can the OLIMEXINO-328 board handle via the (lipo) battery connector?  The reason I am asking is I have many, many rechargeable AA batteries and only 1 3.7 volt lipo battery.   If I wired up 4 AA batteries that would be about 1.2 x 4 = 4.8 volts.  Would that be too much?

Thanks.

[JohnS]

It's unlikely to charge them.

At a glance the cct looks like it'll stand them but you'd have to check datasheets for each appropriate device.  USB won't work, nor anything else that needs the 5V line.

John

[Lurch]

You should be OK with the 4.8V - but the charger circuit (MCP..) won't recharge the batteries.  It cuts off at a voltage of 4.2V, which is fine for LiPo batteries.  By the time your pack of 4 drops to 4.2V they may be close to damaged by deep discharge.  Using 3 AAs would probably work better.  As mentioned above, you should also check the charge current to see if it might exceeds the value the AAs can stand.

[Kurt]

This board, when using a 3.7 volt lipo battery attached via the lipo battery connection... it does not work when run at the 5 volt setting?  When using a 3.7 volt lipo battery via the lipo battery connection the board should be set to the 3.3 volt setting?

[JohnS]

What in the User Manual (or schematic or elsewhere) is making you think that?

John

[Kurt]

This is what I am trying to do (and this is my first Arduino project):

I have an Arduino board with an SD shield and an ultrasonic sensor.  The idea is to use this to measure the water level in a stream in a nearby wetlands.   The system works fine in that it measures the distance and records it on the SD card once every 15 minutes.  Since there is no convenient electrical outlet in the wetlands I have been researching and testing low power options.

First I just tested by running the system on a battery of more less known amp hours (9 volt, bank of 8 AAs, etc.) and divided the number of hours of recorded data to get an estimate of power consumption.

Then I put together a little system using Adafruit's INA219B Current Sensor Breakout to measure it more directly.  http://learn.adafruit.com/adafruit-ina219-current-sensor-breakout

Nobody should take these readings as gospel as I mentioned at this point I haven't even completed my first Arduino project:

                     Sleep Test       Setup /w SD Shield & Sensor            
               Active Sleep            Active Sleep      Daily
Adafruit Board                              
   @ 5.0 volt         54   36      79   63      1512
                              
SarinSmart                              
   @ 5.0 volt         60   43      82   67      1608
   @ 3.3 volt         34   27      54   48      1152
                              
Olimex 328 (on regular Battery)                              
   @ 5.0 volt         27   12      46   33      792
   @ 3.3 volt         14   9      31   25      600
                              
Olimex 328 (on 3.7 volt LIPO Battery)                              
   @ 5.0 volt                           
   @ 3.3 volt         12   4      23   16      384


Here is my sleep code test:

Code Select Expand

#include <lowpower.h>

void setup()
{

} // setup

void loop()
{
     
   LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); 
   
   delay(2000);   
     
} // loop

I sampled the current every 1 second so I see the nice 2 second peak in the delay(2000) in the sleep test.  The Adafruit board used 54 mah when it was active and 36 mah when it was asleep (in the sleep test).  When it is used with the SD card shield and ultrasonic sensor it uses 79 mah when active and 63 mah when sleeping.

When I try the Olimex 328 powering it via the lipo battery with it set to 5 volts the INA219B registers 0.6 mah and nothing seems to work – as it doesn't record any sensor data.  It does not record any sensor data at the 3.3 volt setting when on the lipo battery but it does show power consumption (see table) and the sensor is a 5 volt sensor so I'm not too surprised.  It all works very nicely when powered via the 2.1mm battery connection.  However I read about http://olimex.wordpress.com/2013/11/05/experimenting-with-low-power-modes-and-arduino/ and wanted to use the lipo battery connector to get to the lowest use of power.

I am using the lowpower library by Rocket Scream Electronics.  Do other low power libraries do a better job?

Thanks for any advice.

[Lurch]

Check the schematic of the 328. It shows that whatever is connected to the LiPo connector is only powering the 3.3V regulator.  It doesn't ramp up the voltage to 5V.
The 328 is otherwise a good solution. You might want to look for someone to change the sensor. Looking at the datasheet for the sensor:

The INA219 senses across shunts on buses that can vary from 0V to 26V. The device uses a single +3V to +5.5V supply, drawing a maximum of 1mA of supply current.

So it could technically run on 3.3V. Don't know the board, though, so can't say if that's feasible.  Maybe create your own sensor board?
<edit: just looked at the breakout - it runs at 3 to 5V, so why not run it a 3.3V?>

[Kurt]

When I have further tested my setup using Adafruit's INA219B on one UNO board which I connect to my Olimexio-328 with the SD card shield and sensor I noticed that the sensor itself is pulling about 12 mA.  (I ran it with the sensor plugged into the +5v on the Olimexio-328 and without it plugged into the +5v on the Olimexio-328.)

I only need that sensor to run for a second or two every 15 minutes.  Is there some way of turning that off and on?

It currently gets it power via the +5v on the Olimexio-328.  Can that pin be turned off via software?  (The one sensor is the only thing using that pin.)  Can I move that line from the sensor off that +5v pin to another one of the digital or analog pins that I can turn off and on via either digitalwrite or analogwrite? 

Other ideas?

Thanks.

[Lurch]

According to the datasheet, the sensor can run at 3,3V - have you tried that?
If it works, you could use the Olimexino_32U4.  It can turn off the 3,3V UEXT supply using pin D8.
Maybe you can use the schematic to make your own power-switch?