i'm currently designing a arduino circuit to run a 2004 lcd through I2C, rfid reader, keypad, and a few switches.
ive been looking at a 11.1 v LI ion battery that can peak at 12.8 volts. would it be possible to uses this for power a arduino mega without causing damage to the voltage regulator or will i need to add one myself.
I would be happy to run this setup.Does not look like too much current.
It can't possibly be a good idea. Your Mega runs on 5v and its regulators are very crude, so the other 6v has to get thrown away as heat. Things get quite hot enough on a 9v wall wart. There is nothing to suggest you need 11v, so why do it? Maybe battery efficiency is of no concern but essentially, the greater the voltage difference, the greater the demand for a quality regulator. People are running Arduino with a single 3.7v cell through a buck converter. You may find that quite satisfactory.
The dispkay and the rf reader need power, likely 5 volt. Use a buck converter that delivers 5 volt to all devices.
You can test that yourself.
Turn everything on and find the voltage regulator on the Arduino Mega board. If you can not keep your finger on the voltage regulator, then it is too hot and the voltage is too high.
I'm with Nick_Pyner and Railroader, I'm not confident that the voltage regulator can handle it, and wasting battery power can be avoided with a DC/DC-converter.
This is what a DC/DC-converter looks like: https://www.pololu.com/product/2831
Or put the three batteries in parallel, and use a 5V boost converter.
ShermanP:
Or put the three batteries in parallel, and use a 5V boost converter.
If the batteries are not matched it truly is a better solution to run them in serie.
Another switching regulator choice
https://www.digikey.com/en/products/detail/murata-power-solutions-inc/OKI-78SR-5-1-5-W36-C/2259781
Check the datasheet on whatever you select, see if any input/output capacitors are needed.
Check shipping costs too.
Railroader:
If the batteries are not matched it truly is a better solution to run them in series.
If the batteries are not matched it truly is a better solution to not run them in series but put them aside and find something more suitable. For LiPo, mismatching in series is worse than mismatching in parallel.
Since you want a consistent regulated 5 V to obtain stable contrast on the LCD display, a USB "Power Bank" may be a workable source. We presume it is intended to be operated consistently for a modest amount of time and not be complicated by power-saving "sleep" measures.
It is not obvious why a Mega 2560 would be wanted. While the main current consumption is the LCD backlight, the USB interface chip is unnecessarily wasting power.
The clear and common blunder is not comprehending what the "Vin" or "RAW" terminal is. The regulator on the Arduino UNO/ Nano/ Pro Mini/ Mega2560/ Leonardo/ Pro Micro has very little heatsink, so will not pass very much current (depending on the input voltage and thus, how much voltage it has to drop) before it overheats and (hopefully reversibly) shuts down. It is essentially a novelty provided in the very beginning of the Arduino project when "9V" power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle.
Nowadays, 5 V regulated switchmode packs are arguably the most readily available in the form of "Phone chargers" and switchmode "buck" regulators to regulate down from 12 V or other available voltages are cheap on eBay so these can be fed into the USB connector or (more appropriately) 5 V pin to provide adequate power for most applications. Unfortunately, many tutorials or "instructables" are seriously outdated or misleading and have not been updated to reflect the contemporary situation.
If powering directly from batteries, as long as the battery pack cannot exceed 5.5 V, this must be connected to the 5 V pin.
@Paul__B
I agree to "find something more suitable.".
I had a buck converter in mind, not written in the reply.
Running batteries in serie and one is mismatched the stack will loose voltage faster, likely one even gets reversed. A mismatched battery, in serie, is easily detected by checking the voltage of each cell in case things start to look strange. Cells in parallell... Practically not that easy to check them up.
Both alternatives have their disadvantages. Specifying the project and then getting the proper components should be the case, not making a project out of the content of the drawer, or ignorance.
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