Suggestion for Power Supply

Hi,

Since I'm doing a project to logging temperature and sending to smart phone over Bluetooth which uses ATmega644, MCP9808 temperature sensor, Adafruit DS1307 Real Time Clock, 20x4 character LCD, MicroSD card breakout , Adafruit Bluefruit LE UART Friend.

I plan to use a lipo 3.7V 2000mhA battery for this project but I have a question.

Seems to me, all components I chose will work fine with 3.7V but it will discharge.
Should I use power booster to keep 5V to power to my project? Is there any drawback from that? I probably have to use some regulator to down 5V to 3.3V to power MicroSD and Bluetooth since it works with 3.3V.

Or should I use regulator from 3.7V-3.3V?

Thank you very much.

I plan to use a lipo 3.7V 2000mhA battery for this project

That might run a setup like you describe for a few hours.

Much better to use house AC power, or carefully study and follow the advice from this tutorial on sleep modes.

definitely use a 110 converter if it doesn't need to be portable...

and the LCD runs better on 5v.

if it needs to be portable, I would suggest using a couple 9v is parallel and a maybe a separate
voltage regulator so the onboard one doesn't get ruined

Thanks, actually it is a portable device project and rechargeable. The goal is to run it few days or a week. Actually, the logging could be 30 min/once. Do you guys think it's possible or any suggestions?

Thank you very much.

trungdn:
Seems to me, all components I chose will work fine with 3.7V but it will discharge.

On what evidence do you think that?

A DS1307 chip requires between 4.5 - 5.5V.

The required voltage for the ATmega644 depends on the clock frequency. 16 MHz isn't guaranteed at 3.7V, but 8 MHz will be fine.

You haven't specified the LCD module at all, so heaven knows what it needs.

The Bluefruit will be fine, it has an LDO built into it.

SD cards require 3.0 - 3.6V. The module you have might or might not have an LDO + level shifter, you have not told use.

I'm no expert. but the 16x2 LCD that comes in all the starter kits are in 5v kits. the 20x4 LCD is pretty much the same thing just bigger.

the only displays I've seen for Arduino use that are 3.3v is OLED's

is there any particular reason for using the 3.7v system that you wanted?
5v is a pretty good standard for your application I would say.

Jiggy-Ninja:
On what evidence do you think that?

A DS1307 chip requires between 4.5 - 5.5V.

The required voltage for the ATmega644 depends on the clock frequency. 16 MHz isn't guaranteed at 3.7V, but 8 MHz will be fine.

You haven't specified the LCD module at all, so heaven knows what it needs.

The Bluefruit will be fine, it has an LDO built into it.

SD cards require 3.0 - 3.6V. The module you have might or might not have an LDO + level shifter, you have not told use.

Thank you very much, Jiggy.
I'm just based on the datasheet to guess if it work with 3.7 or 3.3V. I'm nervous to burn it if directly plug to the battery. Right now, I'm still using 5V booster but I think about why I should boost it up and then shift it down to 3.3 for other components. Maybe it will save more power.

You are right, but I can use DS3231 which support 2.3-5V to solve the problems.
ATmega644, I haven't test with it but as you said it probably will work with 3.7V
Screen I tested with 3.3V and I also have an OLED which works with 3.3V
SD card and Bluefruit both have LDO and level shifter in. I think it will be ok

Also, the most important reason I think I should create another topic.
The Inductor from my power booster keep burning for no idea, I'm not sure if you face with this problems before. I ordered some Inductors but some can last for few days, one burn when I just solder to the breakout.
I guess it could be overheating problem.

Thanks.

LandonW:
I'm no expert. but the 16x2 LCD that comes in all the starter kits are in 5v kits. the 20x4 LCD is pretty much the same thing just bigger.

the only displays I've seen for Arduino use that are 3.3v is OLED's

is there any particular reason for using the 3.7v system that you wanted?
5v is a pretty good standard for your application I would say.

Thanks, I have a OLED and tested with it as well. It works.
Since I want to save more power, I think why I should power it to 5V and then shift down to 3.3V for the SDcard and Bluetooth.

And for some reason, the Inductor from my power booster is burning which I have no idea.

can you get two of those batteries and put them in series then you can have separate voltage regulators.

one for 5v components and the other for 3.3v components.

not sure how feasible that is for you as far as this particular project goes

LandonW:
can you get two of those batteries and put them in series then you can have separate voltage regulators.

one for 5v components and the other for 3.3v components.

not sure how feasible that is for you as far as this particular project goes

Thank you, since I also want to keep the size of project as small as possible.
But it's a good idea.

trungdn:
And for some reason, the Inductor from my power booster is burning which I have no idea.

"Burning" being...what? Catching fire? Fusing open?

Check your polarity on the input voltage. If it's reversed the supply will be loaded by an inductor and a diode (the MOSFET body diode), which will probably blow something if the input doesn't have overcurrent protection.

There's a good chance the regulator chip is blown too.