Arduino pro mini v5 on-board MIC5205 150mA LDO Regulator

Other Hardware Motors, Mechanics, Power and CNC
1

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 ( Search results for: 'batteries lipo batteries eflite umx beast type lipo battery' )

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

Thank you for your time :slight_smile:

2

Have you ruled out 3.7V operation then? The 3.3V 8MHz Pro Mini uses about half the current
as well as less voltage. That would give you 2 to 3 times the battery life for the same mass
of battery.

3

Lets say I connect a 240mAh 1S 3.7v 25C LiPo Battery with a 5V Step-Up Regulator to the Arduino pro mini v5 VCC pin bypassing the linear voltage regulator. Does that sound better?

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 the Voltage regulator will discharge the battery to 2.7V causing irreversible damage which will deteriorate the battery performance and cycle life.

If I disable the Arduino on-board power LED and since I am bypassing the Linear regulator in sleep mode the current consumption will be 0.0058 mA, so if I use the SparkFun LiPo Fuel Gaugeprogram and program the Arduino to enter sleep mode at 3V will this be good enough to protect the LiPo battery?