Voltage regulator for battery powered microcontroller

Thread Starter

EriBoo

Joined Feb 9, 2022
9
Hi folks,

I think what I have is a fairly simple question, yet I've spent so much time Googling, that I've completely lost track of what is what.

I'm looking for an affordable voltage regulator to power an ESP32 from a number of AA or AAA batteries.

I have bought a pair of these (Dutch webshop, but English page, the PCB is only marked "S08 v5.0") and they are great, except for two things: a) they're relatively expensive (€3.00, the ESP32's they'll power are cheaper when ordered from China) and b) with a minimum input voltage of 2.5V they don't allow for the option to power the ESP32 off of a single AA-battery.

I also found the Pololu 3.3V Step-Up Voltage Regulator U1V10F3 (which is also a down regulator when the input voltage exceeds 3.3V according to the description), which would solve the second problem, but that is fairly expensive again at $6.95 a piece.

So basically my questions:

  • If you were to source a 3.3V voltage regulator for a microcontroller to be powered of batteries, what'd you buy?
  • What would you use if the 'single AA-battery'-option wasn't a requirement?
  • Would you know of a cheaper option for where to buy the "S08 v5.0" regulator PCD I've previously bought for €3.00/p?
  • Would you know of an option that could supply either 3.3V or 5V?
  • Can you help me to better search terms that would aid my hunt for this part? I've mostly used 'voltage regulator', 'voltage converter', 'buck boost converter', etc., but maybe I'm way off base here.

I'll happily purchase from AliExpress or an equivalent Chinese vendor and wait for month. I'll probably need quite a few to automate/create sensors for a ton of things in my home, so little savings add up :)

Thanks in advance for your time!
 

ericgibbs

Joined Jan 29, 2010
15,516
hi Eri,
I would choose a battery based on the purpose of the project, the ESP32 in RF mode requires a fair amount of current.
Also, is your project placed in 'sleep' mode etc., driving any peripheral devices.

Do you have details of the full project, to post.?

E
 

Thread Starter

EriBoo

Joined Feb 9, 2022
9
hi Eri,
I would choose a battery based on the purpose of the project, the ESP32 in RF mode requires a fair amount of current.
Also, is your project placed in 'sleep' mode etc., driving any peripheral devices.

Do you have details of the full project, to post.?

E
Hi, thanks for the quick reply!

I've done a quick (and not very scientific) measurement of the power draw using one of those USB port voltage and current displays, and it draws so little current that it doesn't even register as having something attached.

One of the things I'll use them for is a connected soil moisture sensor for all my plants (that'll be around ~15-20 pieces). The ESP32 will be in deep sleep most of the time, where according to Espressif's data sheet it'll draw around 10 micro amps (that's micro, not milli, intentionally) of current. It'll wake up at a set interval (probably once an hour), take a measurement, connect to Wifi, make an HTTP request, disconnect from Wifi and go back to sleep (I'm not a 100% sure how long taking the measurement takes yet, but the rest of the process lasts about ten seconds). I expect to get fairly reasonable battery life out of that.
 

Ya’akov

Joined Jan 27, 2019
5,659
You need to be careful about terminology.

A voltage regulator is a device that takes a higher voltage (exactly how much higher it has to be varies with the type) and provides a stable, lower voltage. Ordinary regulators need about 2V more (called dropout) and so are often not useful for battery operated circuits.

An LDO voltage regulator is a type of regulator with “low dropout”, hence LownDropOut. LDOs require far less, sometimes less than a volt but there can be a cost. Some LDOs require an external capacitor, and if it is not implemented properly the regulator can become unstable. “Capacitorless“ or “capless” LDOs avoid this but can have poor noise and transient performance.

All types of linear regulators are inefficient in proportion to the magnitude of the voltage they must drop. The excess voltage is turned to heat and this is just wasted power. For a battery powered device this is not a good thing.

A switching regulator is a type of regulator that operates like a switching power supply. Instead of turning the excess voltage to heat, it turns the DC to AC at a high frequency and conducts proportionally to the desired percentage of the input voltage. The circuit is also capable of increasing the voltage as a tradeoff for current, so there are two types:

A buck converter reduces the voltage
A boost converter increases the voltage

A third type—buck-boost converteris just a combination of the two and is able to decrease or increase the input voltage.

But, while switching regulators are more efficient from the point of view of power consumption, they are far more complex than linear regulators requiring several parts aside from the controller IC including an inductor, a cap, and some resistors at a minimum.

So, if you want a boost converter that will produce a relatively large current it will be big and expensive compared to a linear regulator. You might be able to build one cheaper than the modules you’ve found but that is generally not the case.

This is one reason people choose to use a single Lithium cell (18650, LiPo prismatic, etc.) and an LDO to get the 3.3V needed for an MCU project.
 

Ya’akov

Joined Jan 27, 2019
5,659
Hi, thanks for the quick reply!

I've done a quick (and not very scientific) measurement of the power draw using one of those USB port voltage and current displays, and it draws so little current that it doesn't even register as having something attached.

One of the things I'll use them for is a connected soil moisture sensor for all my plants (that'll be around ~15-20 pieces). The ESP32 will be in deep sleep most of the time, where according to Espressif's data sheet it'll draw around 10 micro amps (that's micro, not milli, intentionally) of current. It'll wake up at a set interval (probably once an hour), take a measurement, connect to Wifi, make an HTTP request, disconnect from Wifi and go back to sleep (I'm not a 100% sure how long taking the measurement takes yet, but the rest of the process lasts about ten seconds). I expect to get fairly reasonable battery life out of that.
if you haven’t already you need to check out Andreas Spies’ YouTube channel. For what you are doing there are few better resources. He has an ESP8266 playlist and others on low power which he covers in depth.

 

BobTPH

Joined Jun 5, 2013
4,897
If you can use two AA or AAA cells in series you might not need a voltage regulator. The voltage does not need to be exactly 3.3V. It can operate down ti 2.3V, though you will likely lose range on the WiFi if it is lower.

Bob
 

Thread Starter

EriBoo

Joined Feb 9, 2022
9
@Yaakov Wow, thanks! That's a more thorough explanation than I could've possibly hoped for, that helps a lot. I will be doing some further reading up on that, now that I have concrete pointers as to where to go next. Appreciate it! Most definitely checking out that YouTube series as well, excellent!

@BobTPH Hmm, that's a good point. I must admit, as a novice it felt a little hacky/dirty to me, but I guess there's no point in overcomplicating if it doesn't actually provide a tangible benefit. Will do some experimenting with that too. Thanks!
 
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