I would like some advice on powering my Mega2560 if possible.
I am making a CamBot and I am powering it from a 13000mAh 2s Lipo. I believe that this means that the battery will put out 8.2v when full and 6v when depleted. I have a 25W DFrobot voltage module (voltage regulator) on board to supply 5v and I believe it has a drop out voltage of 0.6v.
The Arduino website stated that you should not supply less than 7v through the Barrel Jack or the Vin pin to power the board. Given that the battery can go as low as 6v What is the best way to power the board?
I would like to run 5v to the 5v pin from the power module (as it is neat) but the website also advises against this as it bypasses the on board regulator.
Can I ignore the websites advice and bypass the on board regulator, should I supply 5v through the USB connector? or is there an even better solution (hopefully neater as this robot looks like a pile of spaghetti).
I believe that this means that the battery will put out 8.2v when full and 6v when depleted.
You have some reasons for believing that? Sounds like nonsense to me.
Given that the battery can go as low as 6v What is the best way to power the board?
I don't accept that as a given.
I would like to run 5v to the 5v pin from the power module (as it is neat) but the website also advises against this as it bypasses the on board regulator.
Bypassing the onboard regulator is fine, as long as you are certain that the input is 5.0V at all times - not 8.2V sometimes and 4.5V sometimes.
I believe that this means that the battery will put out 8.2v when full and 6v when depleted.
You have some reasons for believing that? Sounds like nonsense to me.
A two cell lipo has a voltage range of 8.4 (full charged) down to 6 volts so sounds like no nonsense to me.
Given that the battery can go as low as 6v What is the best way to power the board?
I don't accept that as a given.
An unprotected lipo can be discharged to destruction so there is some lower cutoff voltage value that must be obeyed
by some means either by protection circuitry or user awareness, but 6 volts for a 2 cell lipo is pretty standard.
A two cell lipo has a voltage range of 8.4 (full charged) down to 6 volts
I would like to run 5v to the 5v pin from the power module (as it is neat) but the website also advises against this as it bypasses the on board regulator.
Bypassing the onboard regulator is fine, as long as you are certain that the input is 5.0V at all times - not 8.2V sometimes and 4.5V sometimes.
I have one arduino board that I have rubber banded a 2 cell lipo battery to it, as it's about the same size. I just wired a power plug and plug it into the arduino's external power connector so as to act like a convenient on/off switch. I did wire a jumper across the external power's series polarity protection diode to 'regain' the .6 voltage drop for the diode to utilize a little more of the lipo's voltage range.
If however the goal is to utilize the battery capacity to maximum efficiency one would use the lipo to drive a 5vdc switching regulator to power the arduino board directly. The way I use external regulated +5vdc for an arduino board is to take a spare USB cable and cut off the PC end and strip out the power and ground wires and solder them to the regulator output. That way you have a convenient on/off connector rather then solder directly to the 5V and gound pins.
Paul - I got this from Wikipedia "The voltage of a Li-poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged), and Li-poly cells have to be protected from overcharge by limiting the applied voltage to no more than 4.235 V per cell used in a series combination."
I assume that the 3v per cell that I have heard about is being cautious and I will be sticking to 3v per cell min before charging. So no, not nonsense at all. As stated, on the robot I have power direct from the Lipo that varies between 6v and 8.4 and from an external 5v regulator so while the power from the external 5v regulator will fluctuate it won’t be anywhere near 8.2v
GrossRoads - Thanks that was the Answer that I was looking for.
retrolefty - Thanks cutting down a usb cord was my second option.
I have my Arduino Mega 2560 running with 5V to the 5V pin all the time.
It is not recommended, but I have that diode over the voltage regulator as CrossRoads wrote. Also my 5V power is not very strong, when I connect the power, there is not an extreme current peak to fill the capacitors. I'm 100% confident that my circuit is safe.
