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Topic: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator (Read 5093 times) previous topic - next topic

majek

To make efficient use of battery, step-up or step-down converter is needed (depends of battery configuration). Good one have efficiency above 90%, 80% is a bad one :-)
Don't use on-board LDO for this.

Most such regulators have 'shutdown' pin. You can get regulator with very low shutdown current (microamps) and implement soft shutdown.

This is my quite old project powered from li-ion batteries with this feature:


On the top-left part of schematic you have power section.
There are 2 components:
- voltage measuring circuit (D1, R7)
- shutdown circuit (D2, R9, C7, D3)

How it works:
Start:
- you press power switch
- C7 is already discharged, so it sets shutdown pin of converter to high
- converter is enabled and passes power to the rest of circuit
- cpu starts
- first thing cpu does is putting PB2 high
- PB2 is connected via diode D2 to shutdown input and it sets high voltage there before C7 is discharged

Stop:
- cpu use ADC to get battery voltage
- if voltage is too low, it finishes all operations and sets PB2 to low
- C7 discharges through R9
- when C7 is discharged, converter stops
- whole circuit draws only converter standby current

Of course it's only one option. If you don't trust your code, it's better to use just battery protection circuit. But soft shutdown is good choice when you need clean shutdown (for example to finish write to sd card etc.).

Wasferd

So this PCB will not work?
Over Discharge Protection   Over Discharge Detection Voltage       2.5±0.063V
                                                    Over Discharge Release Voltage           3.0±0.075V

http://www.all-battery.com/protectioncircuitmodulepcbfor37vli-polymerbattery15alimit-pcb1s.aspx

Wasferd

To make efficient use of battery, step-up or step-down converter is needed (depends of battery configuration). Good one have efficiency above 90%, 80% is a bad one :-)
Don't use on-board LDO for this.

Most such regulators have 'shutdown' pin. You can get regulator with very low shutdown current (microamps) and implement soft shutdown.

This is my quite old project powered from li-ion batteries with this feature:


On the top-left part of schematic you have power section.
There are 2 components:
- voltage measuring circuit (D1, R7)
- shutdown circuit (D2, R9, C7, D3)

How it works:
Start:
- you press power switch
- C7 is already discharged, so it sets shutdown pin of converter to high
- converter is enabled and passes power to the rest of circuit
- cpu starts
- first thing cpu does is putting PB2 high
- PB2 is connected via diode D2 to shutdown input and it sets high voltage there before C7 is discharged

Stop:
- cpu use ADC to get battery voltage
- if voltage is too low, it finishes all operations and sets PB2 to low
- C7 discharges through R9
- when C7 is discharged, converter stops
- whole circuit draws only converter standby current

Of course it's only one option. If you don't trust your code, it's better to use just battery protection circuit. But soft shutdown is good choice when you need clean shutdown (for example to finish write to sd card etc.).

Would I be able to use the SparkFun LiPo Fuel Gauge and program the Arduino to enter sleep mode at 3V?
If I disable the power LED and since I am bypassing the Linear regulator the current consumption will be 0.0058 mA    is that good enough?

https://www.sparkfun.com/products/10617

http://www.home-automation-community.com/arduino-low-power-how-to-run-atmega328p-for-a-year-on-coin-cell-battery/

somedude

Hey,
So you reckon powering the mini with 4.8V is better than using a 7.4V?

I was merely suggesting it as a possible option, since the voltage is so close to operating voltage and it doesn't need to be dropped as much, possibly giving you better efficiency.

john1993

most efficient solution is running an m328 directly off 1s lipo.  avr can monitor voltage and shut down to virtually zero current at any point.  promini is not capable of this and rube goldberg regulator schemes a huge waste too. kiss.

majek

most efficient solution is running an m328 directly off 1s lipo.
Except if  you have bunch of 5V powered peripherials as in that case...

Would I be able to use the SparkFun LiPo Fuel Gauge and program the Arduino to enter sleep mode at 3V?
If I disable the power LED and since I am bypassing the Linear regulator the current consumption will be 0.0058 mA    is that good enough?
What about other parts? Could you put them into sleep mode as well?

If you need to protect battery, you need to really shut down everything, to single microamps.
About battery protection - check step-up converters as some of them already have such protection.

john1993

Except if  you have bunch of 5V powered peripherials as in that case...
after a brief glance i suspect in addition to the avr that "myoware", rf, and flash card all capable of 3v operation.  possibly all have sleep mode too and if not a penny pfet would take care of that.

also note that most switching converters generate orders of magnitude more noise which might wreak havoc with the emg and rf.  of course efficiency and economy are not always the chosen path.  many find the whole concept of simplicity abhorrent, specially on the internet.

"The cheapest, fastest, and most reliable components of a system are those that aren't there." -Graham Bell



Wasferd

Except if  you have bunch of 5V powered peripherials as in that case...
What about other parts? Could you put them into sleep mode as well?

If you need to protect battery, you need to really shut down everything, to single microamps.
About battery protection - check step-up converters as some of them already have such protection.

Wouldnt all the peripherals cease working if the Arduino is put in sleep mode?

majek

Wouldnt all the peripherals cease working if the Arduino is put in sleep mode?
They stop working, but they don't stop draw current until you put them into sleep or cut them power if sleep mode is unavailable.
You need to study datasheet of all your peripherials if you want to go this way.

Wasferd

Alright, so here are my components:
1) Arduino Pro mini 5V ( Typical supply voltage: +5.0 V, Typical supply current: 10-25 mA)
2) Transmitter Module ( Typical supply voltage: +5.0 V, Typical supply current: 03-10 mA)
3) Myoware muscle sensor ( Typical supply voltage: +5.0 V, Typical supply current: 09-14 mA)

They are going to be integrated into a 3D-printed wristband. Hence the battery needs to be small and light. There is no minimal operational time requirement. However the longer the better.

I intend to power through the VCC pin bypassing the Arduino on-board linear voltage regulator.
I am thinking of using this Lithium Ion Polymer Battery - 3.7v 500mAh with a 5V Step-Up/Step-Down Voltage Regulator. The battery has its own PCB that will cut-out the battery when completely dead at 3V.
So Ill have the LiPo battery connected to an external switching voltage regulator connected to the VCC pin.

http://www.adafruit.com/products/1578
https://www.sparkfun.com/products/10255

How does that sound? am I missing anything? I will possibly also use the SparkFun LiPo Fuel Gauge to monitor the battery voltage as an extra measure of safety.

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