I am trying to figure out how to supply my 3.3v iot sensor circuit with power. With a small research I can see that the optimum solution is to use Lipo & Li-Ion batteries. Yet, I faced a simple problem, which is charging and protection circuit. I tried to use TP4056 lipo charging circuit .. (atleast this is how they call it).
A simple issue that arose was that my circuit needs to maintain a 3.1¬3.4 voltage supply and that "TP4056 circuit" won't simply work. 2 issues are that I need to step down my voltage to 3.3 from 4.2 (at the fully charged case) - which will never work with a normal LM1117 since after test Vin should be at least around 4.5V; other than that, the output voltage would be lower than 3V. Another issue was that the "TP4056" cuts off the voltage at 2.4~2.5V .. at this stage my circuit will not work at all, and - assuming I could step down the voltage with some other IC - almost 30% of my battery's life would be simply useless.
A solution to this issue would be using an auto 3.3v step up/step down IC but I can't seem to find a good one. (Any Suggestions?)
Another that I thought of was connecting 2 series Li-Ion batteries to get a voltage that is higher than 5V and easily step down to 3.3V. Yet, I can't figure out connecting the batteries to protection/charging circuit. I found out that BMS circuit won't be useful in charging and clearly I can't use TP4056 for such a series connection as one of the TPs +vout would be connected to the common ground which will cause a short circuit.
Now I am out of solutions and looking for more from your side. Or just simply help me see what have I done wrong in my previous approaches.
PS: I would like my circuit to be charged by a USB (5V) cable.
What IOT sensor circuit.
Take the WeMosD1 mini, with it's ESP-12 module (ESP8266 MCU).
They have an onboard 3.3volt regulator with a dropout voltage of ~0.1volt at 200mA.
Not a problem to power that module directly from a single LiPo batery.
The LM1117 is not suitable for this. Leave that one for the 5>3.3volt projects.
Leo..
Wawa:
What IOT sensor circuit.
Take the WeMosD1 mini, with it's ESP-12 module (ESP8266 MCU).
They have an onboard 3.3volt regulator with a dropout voltage of ~0.1volt at 200mA.
Not a problem to power that module directly from a single LiPo batery.
The LM1117 is not suitable for this. Leave that one for the 5>3.3volt projects.
Leo..
Hi Wawa,
I am using ESP8266-01 and I am pretty comfortable with it..
I don't see the difference between the WeMosD1 and ESP8266-01 in terms of power supply. The 5v and 3.3v volt supply in addition to the extra i/o pins might be useful in other applications. For mine I only need one I/O (I am using GPIO2, plz correct me if it's wrong). From what I see, the WeMos is powered by a usb .. it can be replaced with a normal 5v input that's then regulated to 3.3v for the esp VCC.
Now how exactly is it "okay" to power it with a lipo battery that has a voltage range of 4.2~2.5v ?!
Even the WeMos schematic sheet says that the ESP8266 VCC Range is 1.7~3.6V which clearly doesn't tolerate the 4.2V input for the lipo battery at full charge. Is it that the regulator onboard of a step down/up function?
An ESP-01 is a bare ESP8266 module with minimal amount of flash and no 3.3volt regulator.
Mainly used as WiFi add-on for e.g. an Uno.
A Wemos (and many others like that) has all the supporting parts to power and program the onboard ESP-12.
The 5volt pin on that board is mainly a power input, with a ~3.5volt to 5volt range.
It normally gets it power from the USB connector, via a diode (with a 0.4volt drop).
But perfectly fine to inject ~3.7volt from a LiPo into the 5volt pin.
I don't bother with all of that, and just power the Wemos with a tiny 5volt/0.5A cellphone charger with USB lead.
One is actually powered via a powerbank that keep is running for 36hours after a power cut.
Bit wasteful, but easy. The powerbank takes care of battery health.
You can ofcourse use that ESP-01, but you must add a very low drop 3.3volt regulator if you want to use a single cell LiPo.
Programming also becomes more of a hassle, and you can't use OTA programming with an ESP-01.
Leo..
Wawa:
An ESP-01 is a bare ESP8266 module with minimal amount of flash and no 3.3volt regulator.
Mainly used as WiFi add-on for e.g. an Uno.
A Wemos (and many others like that) has all the supporting parts to power and program the onboard ESP-12.
The 5volt pin on that board is mainly a power input, with a ~3.5volt to 5volt range.
It normally gets it power from the USB connector, via a diode (with a 0.4volt drop).
But perfectly fine to inject ~3.7volt from a LiPo into the 5volt pin.
I don't bother with all of that, and just power the Wemos with a tiny 5volt/0.5A cellphone charger with USB lead.
One is actually powered via a powerbank that keep is running for 36hours after a power cut.
Bit wasteful, but easy. The powerbank takes care of battery health.
You can ofcourse use that ESP-01, but you must add a very low drop 3.3volt regulator if you want to use a single cell LiPo.
Programming also becomes more of a hassle, and you can't use OTA programming with an ESP-01.
Leo..
Thanks for the response Leo.
It's just that we can't seem to get to a useful point, replacing the hardware isn't always the best suggestion to make. But that's fine since my questions was obscure and not clear enough.
If I have a 5V power supply from let's say a usb cable as an option, I wouldn't bother posting here and I would just use a 3.3V regulator! My sensor circuit along with the esp is at the lowest current usage so the battery should last for weeks. And since this is a semi professional solution, I wouldn't use "a power bank".. this simply doesn't add anything to the table.
So let me be more clear about what I am seeking. I am using ESP8266-01 which requires an input of a 3.3V. What circuitry do you suggest to regulate a 2.5~4.2V lipo battery input (connected to a TP4056 protection circuit) to 3.3V ?
Forget about LiPo voltage below ~3.4volt.
There is not much power left in the battery below that.
Find a 3.3volt linear regulator with ~0.1volt max dropout at 200mA, like the ones being used on a WeMos etc.
And use that between the battery and the ESP-01.
A 470uF cap on that 3.3volt line might help that regulator bridge the ~400mA transmit pulses of the ESP.
Leo..