# Arduino Forum

## Using Arduino => Microcontrollers => Topic started by: Wasferd on Nov 21, 2015, 10:14 pm

Title: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 21, 2015, 10:14 pm
I am currently working on a hand prosthetic and am developing a wearable wristband to read emg signals. The wristband contains the following:

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)

I am currently looking for a battery to power these components. The battery needs to be as small and as light as possible. It also needs to be rechargeable. There is no minimum operation time due to the project being a prototype, however, the longer the duration the better. I am currently looking at the s 200mAh 2S 7.4v 20C LiPo Battery ( http://www.overlander.co.uk/batteries/lipo-batteries/eflite-umx-beast-type-lipo-battery.html )

QUESTION 1) Will this battery work fine with the components mentioned above?

QUESTION 2) will it work for roughly hours as I calculated?

0.2 Ah /(25 mA+10 mA+14 mA)= 4 h

QUESTION 3) looking at the Arduino on-board voltage regulator (http://www.micrel.com/_PDF/mic5205.pdf) I calculate that there will be 0.379 W power dissipation is the value correct?

Pd=(7.4 V-5 V)*150 mA + 7.4 V *2.5 mA = 0.379 W

QUESTION 4) I also calculate that the voltage regulator temperature rise will be 83.83 C is the vale correct and is it normal or do I need a heat sink?

TempRise= 0.379 W*220 = 83.83 C
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: somedude on Nov 21, 2015, 11:04 pm
4.8V batteries may be smaller and more suitable for your project. Just a thought.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 21, 2015, 11:19 pm
Hey,
So you reckon powering the mini with 4.8V is better than using a 7.4V?
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: westfw on Nov 22, 2015, 02:28 am
Quote
QUESTION 3) looking at the Arduino on-board voltage regulator (http://www.micrel.com/_PDF/mic5205.pdf) I calculate that there will be 0.379 W power dissipation is the value correct?

Pd=(7.4 V-5 V)*150 mA + 7.4 V *2.5 mA = 0.379 W
No, because you're not actually using 150mA.  And the 7.4V is "nominal" for a 2s LiPo pack (more like 8.4 initially.)
so, more like (worst case): Pd=(8.4 V-5 V)*(25 mA+10 mA+14 mA) + 8.4 V *2.5 mA

You might be a lot better off using a 1S LiPo and a boost regulator to get 5V, since a boost regulator will give you 80+% efficiency, while the linear step down is worse than 50%...

Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 04:05 am
Thanks for the insight. So a 240mAh 1S 3.7v 25C LiPo Battery with a 5V Step-Up/Step-Down Voltage Regulator would the job?

https://www.coolcomponents.co.uk/5v-step-up-step-down-voltage-regulator-s7v8f5.html
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: CrossRoads on Nov 22, 2015, 04:47 am
Yes, that should last a few hours per charge. Maybe 4 to 5.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 04:48 am
Would  I need a PCB for the LiPo battery or is that unnecessary?
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: CrossRoads on Nov 22, 2015, 06:14 am
Not needed, just the connector.
For example, this remote control use a 3.3V/8MHz Promini running from a 1000mAH LiPo that is tiewrapped to the bottom of the card. A Max1811 (not plugged in here) is used to charge the battery from a 5V source (such as USB).
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: CrossRoads on Nov 22, 2015, 06:17 am
Here's the circuit
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 06:40 am
But the battery datasheet says "Never discharge Li‐Po battery below the Lowest Discharge Voltage 3v per cell"

and the voltage regulator data says "takes an input voltage from 2.7 V to 11.8 V and increases or decreases the voltage to a fixed 5 V output'

Thus wouldn't the Voltage regulator discharge the battery to 2.7V causing irreversible damage which will deteriorate the battery performance and cycle life ?

https://www.pololu.com/product/2123
http://www.overlander.co.uk/fullymax_warning_sheet_li_poly.pdf

Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: CrossRoads on Nov 22, 2015, 06:53 am
If you look at the schematic, you will notice I am powering the promini via the VCC pin, not Raw, so the onboard regulator is bypassed. The battery never sees more than 4.2V from the max1811 charge control chip.
The promini goes into power down sleep mode after waking up from a button press and transmitting the character via virtualWire library.
The battery lasts about a month between charges, when I notice that it is not sending anymore I plug it in to charge it.
A battery disconnect transistor would probably be good to keep the battery from overdischarging.
At the same time, it's been running like that since ~Jan 2011. Maybe battery life has been degraded some, I don't monitor it all that closely.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 07:08 am
I also intend to power through the VCC pin bypassing the linear voltage regulator.
So Ill have the LiPo battery connected to an external switching voltage regulator connected to the VCC pin. The external voltage regulator I have been referring to will discharge a battery to 2.7V which is smaller than the limit of >3V LiPo cell discharge.  Perhaps I am misunderstanding something.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: CrossRoads on Nov 22, 2015, 07:40 am
You'll have the battery connected to the input of a switching regulator, with nothing to stop the regulator from overdischarging the battery?  Yes, that could lead to battery issues.
You need a part like this to disconnect the battery from the load
https://www.sparkfun.com/datasheets/Prototyping/tps61200.pdf (https://www.sparkfun.com/datasheets/Prototyping/tps61200.pdf)
Values here may need adjusting to meet 3V instead of something lower
https://www.sparkfun.com/products/10255 (https://www.sparkfun.com/products/10255)
You need a battery charge control circuito to charge the battery still.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 07:48 am
The two components seem rather complex. Is there no simpler solution to breaking a circuit when battery input voltage is lower than a set limit?

For example will this PCB disconnect the circuit at 3V ?
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

For charging the Battery can't I use something as simple as this ?http://www.overlander.co.uk/chargers/lipo-battery-balance-chargers/overlander-rc3-lipo-charger.html
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Paul__B on Nov 22, 2015, 09:55 am
The two components seem rather complex. Is there no simpler solution to breaking a circuit when battery input voltage is lower than a set limit?
Probably not.

Disconnecting a battery below a certain voltage is a particularly complex problem, since the circuit which does this must draw no current once disconnected, but draw no current when connected either as clearly that would actually discharge the battery - the very thing you need to prevent.

This rules out for example Zener diodes as threshold references; the entire circuit must be CMOS.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: majek on Nov 22, 2015, 12:24 pm
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:
(http://majek.mamy.to/gps/zdjecia/gps.png)

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.).
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 12:44 pm
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
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 01:01 pm
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:
(http://majek.mamy.to/gps/zdjecia/gps.png)

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/
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: somedude on Nov 22, 2015, 01:29 pm
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.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: john1993 on Nov 22, 2015, 02:14 pm
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.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: majek on Nov 22, 2015, 05:55 pm
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.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: john1993 on Nov 22, 2015, 06:41 pm
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

Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 06:54 pm
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?
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: majek on Nov 22, 2015, 08:17 pm
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.
Title: Re: Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator
Post by: Wasferd on Nov 22, 2015, 08:29 pm
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.