Hello
Question:
I have a 3V7 Li-On battery AND I want to use it like a 3V3 volt power supply. Okay then... what do I need to get a 3V3 voltage level ?? Add a diode with a forward voltage 0.4 Volts maybe?
Edit: Or can i connect directly to atmega vcc pin using a bypass condenser ? I read this: It operates ranging from 3.3V to 5.5V (ATmega 328)
Thanks very much
The thing (or at least a thing) with batteries is that the voltage varies with charge and with current draw.
Given the operating range of the ATmega328, you can power it with just that battery.
But whether you should do so depends on what else is it going to connect to and how is that powered and/or what their operating voltage range is.
On a freshly charged battery you may fry clamping diodes on a 3.3V chip you connect to, or on a low battery your high output levels may not be high enough for a 5V chip.
Whether and what kind of regulation to use depends on the application.
The current draw of the micro is probably/presumably going to be very uneven and most of the time very low, so the voltage drop of that diode is also going to vary.
And yes, regardless of how you power the ATmega, put a ceramic capacitor across the power pins close to the chip for decoupling.
Oh, I see.
So what is the best solution when you want to avoid use voltage regulator to carry the current consumption a minimum level while the arduino is low power / sleep mode ?
Because if I only have a 3.7V battery then I will need to do this:
3V7 >> Step Up >> 5V >> Linear Regulator>>3V3>> ATMega328
gpssignal:
...Because if I only have a 3.7V battery then I will need to do this:3V7 >> Step Up >> 5V >> Linear Regulator>>3V3>> ATMega328
i believe that is the norm - the number of boards/battery shields out there that use an 18650 holder and USB port would use that setup exactly.
just don't see it as "inefficient" (going up then down) but a proper way to manage your power demands.
a "single component/module" alternative would be a SMPS DC-DC step-down converter - 3v7 to 3v3.
First its essential to realise that a so called 3.7v battery will likley be 4.2V when fully charged.
There are low dropout 3.3V regulators, such as MCP1700, that are quite happy to take the batttery output and turn into 3.3V regulated. This regulatoir will stop regulating (@250mA) when its input falls to 3.5V, but by then your battery is fairly flat anyway.
You are asking the wrong question, assuming you are onabout your last thread SDCard directly to Arduino 3V3 - #5 by gpssignal - General Electronics - Arduino Forum
You need 3V3 not for the processor but for the SD card you want to attach to it.
You should not have started a new thread.
Grumpy_Mike:
You are asking the wrong question, assuming you are onabout your last thread SDCard directly to Arduino 3V3 - #5 by gpssignal - General Electronics - Arduino ForumYou need 3V3 not for the processor but for the SD card you want to attach to it.
You should not have started a new thread.
I need 3v3 volt for the microprocessor and SDCard. I said before I dont want use regulators, BUT now I can understand I will not able to do, because if I use 5V then I will have a 5v5 to 3v3 regulator, if is 3v7/4v2 I will use 3v7/4v2 to 3v3.
Okay so, what is the best voltage operation option to use 3.7V battery powered project using arduino, 3v3 or 5v ??
if you want "moderator" / Administrator, please delete the thread SDCard directly to Arduino 3V3 - #5 by gpssignal - General Electronics - Arduino Forum
gpssignal:
Okay so, what is the best voltage operation option to use 3.7V battery powered project using arduino, 3v3 or 5v ??
'Best' would depend on the particular project, you have not told us what that is.
srnet:
'Best' would depend on the particular project, you have not told us what that is.
small project battery powered (3.7 Li-On) where the modules include SIM7600 module, SDCard module, Arduino mini 3V3/5V, analog sensor 0.5-4.5V output and maybe a real time clock module.
I need 3v3 volt for the microprocessor and SDCard.
Yes but have not told others here on this thread. While you do not need anything to run the ATmega328 of a low voltage the fact that you need to power an SD card from the processor’s supply means it can not exceed the voltage requirement of the SD card.
A list of parts does not say what you want to do with these parts.
Grumpy_Mike:
Yes but have not told others here on this thread. While you do not need anything to run the ATmega328 of a low voltage the fact that you need to power an SD card from the processor’s supply means it can not exceed the voltage requirement of the SD card.A list of parts does not say what you want to do with these parts.
I want remove the 5V to 3V3 volt linear regulator for each modules. The main reason is save power of battery when I disable the modules.
Okay if all is so complicated, simply I will use a 5V step up from 3V7 battery. Then I will disable each module complety using a load switch controlled by arduino.
But, in this way I will have a STEP UP converter running always, even in sleep mode / low power of arduino 
Thanks
A LiPo battery produces 3.2-4.2V. The first when it's about to die (truly die, not just go flat); the second is when it's fully charged.
I have seen 3.3V devices that can happily take 5V (the Pro Mini 3.3V is one of them), others that prefer it lower (1.8-3.6V or so - many sensors are in that category).
The SIM7600 you mention in your other thread (why not just one??) requires 3.0-3.6V.
All in all it comes down to what your peripherals need, in both voltage and current. The MCP1700 will do the very low dropout, but maybe not the current required to run a SIM module - the SIM800 series needs some serious peak currents when connecting to a network; probably yours needs as well. The 250 mA the MCP1700 can deliver may simply not be enough.
Another way to get to 3.3V is to use a buck/boost converter - they can go both ways. Just adding a 3.3V buck converter to your battery may not work; they may also have minimum dropouts.
gpssignal:
I need 3v3 volt for the microprocessor and SDCard.
Then you must use a 3.3V regulator (and a very low drop-out one).
SDcard should never see more than 3.3V.
Okay guys
I understand your answer. So I will use a step up boost converter from 3.7V to 5V @ 3A.
Then I will use the main 5V internal plane on PCB and 3V3 volt regulator for each section/module.
I will use a level shifter for SDcard and yes, for the SIM7600 I'll use Tantalum Capacitor and MIC29302WU-TR Linear Voltage Regulator.
I think i will add a jumper to can disable the led status/clock/netlight to save some power.
Do you have anything that needs 5V or can you run everything at 3.3V?
Is it possible to use 2 batteries, so you can step down from 7V?
Bad idea. That boost converter may be quite efficient (losing just 10-15%) but your linear regulator loses 34% no matter what. That's nearly half the energy of your battery being converted to heat, instead of doing something useful for you.
There exist boost/buck converters that can go both ways. That may be a solution. I was actually quite surprised to see the SIM7600 not being able to run directly off a 3.7V battery, many GSM adapters are designed to do just that.
Looking at the datasheet of the MIC29302 it looks like the drop-out is low enough to have it run directly from your battery. No need for the boost converter.
The thing is, most of your components will not draw much power normally, just spikes. Check the actual power consumption. You may be able to get it done with the MCP1700 and a big-ass capacitor (maybe even a small supercap) to support the spikes on the 3.3V side. I'm thinking of a capacitance in the order of 1-100 mF (that's m, not µ).
Jobi-Wan:
Do you have anything that needs 5V or can you run everything at 3.3V?
Is it possible to use 2 batteries, so you can step down from 7V?
Mmm...
ATMega2560 use 5V, SIM7600 use 3.8V, SDReader 3.3v, Sensor 5V... Before I was thinking in ATmega328 to run 3.3V but always the 5V sensor was a problem. Maybe I could use a external circuit to convert the 0.5-4.5V output sensor TO 0-3v3 volt, but It was more simple use 5V for main power supply.
wvmarle:
Bad idea. That boost converter may be quite efficient (losing just 10-15%) but your linear regulator loses 34% no matter what. That's nearly half the energy of your battery being converted to heat, instead of doing something useful for you.There exist boost/buck converters that can go both ways. That may be a solution. I was actually quite surprised to see the SIM7600 not being able to run directly off a 3.7V battery, many GSM adapters are designed to do just that.
Looking at the datasheet of the MIC29302 it looks like the drop-out is low enough to have it run directly from your battery. No need for the boost converter.
The thing is, most of your components will not draw much power normally, just spikes. Check the actual power consumption. You may be able to get it done with the MCP1700 and a big-ass capacitor (maybe even a small supercap) to support the spikes on the 3.3V side. I'm thinking of a capacitance in the order of 1-100 mF (that's m, not µ).
Yes I know (but I am not expert) that Linear Regulator are not good for a battery powered project. But the 5Volt sensor actually is a big problem, with output of 0.5 to 4.5 volts.
To avoid lose a lot of power I will control the modules power on/off using a load switch from MCU.
I will search for your IC and the SIM7600 need 3.8V recommended. I could connect directly to battery I will thing your idea a bit more.
The MCP1700 Rated 250mA Output Current only. SIM7600 need peak of 2A
gpssignal:
Yes I know (but I am not expert) that Linear Regulator are not good for a battery powered project. But the 5Volt sensor actually is a big problem, with output of 0.5 to 4.5 volts.
Which exact sensor is that? No 3.3V version or replacement of it?
To avoid lose a lot of power I will control the modules power on/off using a load switch from MCU.
Use the Enable pin of modules when available.
the SIM7600 need 3.8V recommended
The SIM7600 datasheet that I found says it needs 3.0-3.6V. Apparently it's designed for 3.3V operation. The capacitor would have to deal with the current spikes.
SD cards can also be pretty power hungry.
gpssignal:
ATMega2560 use 5V,
Why not a 328p? I don't see any reason for the 2560 based on your component list. The ATmega328p runs fine on 3.3V, 8 MHz. At that speed it runs at anything from 2.4V up to 5.5V.
wvmarle:
Which exact sensor is that? No 3.3V version or replacement of it?Use the Enable pin of modules when available.
The SIM7600 datasheet that I found says it needs 3.0-3.6V. Apparently it's designed for 3.3V operation. The capacitor would have to deal with the current spikes.
SD cards can also be pretty power hungry.
Why not a 328p? I don't see any reason for the 2560 based on your component list. The ATmega328p runs fine on 3.3V, 8 MHz. At that speed it runs at anything from 2.4V up to 5.5V.
2560 instead of 328p because 2560 has 256kB flash memory. I am not sure if 328p has enough memory also IF I use 3v3 volts, how I said before, The sensor 5V anyway will need 5V step up. So I will use the same 5V line for ATMega2560 and avoid rescale the 0.5-4.5 analog output of sensor
I made first version using 328p and SIM800C, now I need a LTE network and I think more memory flash simply. I I would like to use more effective/addecuate sensor but I only adapt my design to the hardware available, sorry for that
My first Idea was use 328p 3V3 @ 8MHZ directly of 3.7 li-on battery and add a load switch for each modules when the 328p is running in sleep_mode... Removing all leds and regulator possible to save power. This idea changed when I knew the sensor We have is a basic sensor 5V power and when someone told me I will need more memory flash to use libraries and code for our project (I'm not embedded programmer)
I would like to test before but I dont have arduino, neither modules 
. I only have a reference circuits of IC manufacturers and my laptop
I dont have two chances to pay a PCBA services.