some specs

A project log for ESP based robots

dropping some thoughts while looking at ESP32 based robot concepts

davedarkodavedarko 06/21/2021 at 14:114 Comments

The ESP32 cam board features an ASM1117-3.3V regulator. This regulator allows for 12V input voltage, but also has a dropout voltage of 1V. With only one cell this would technically not even work, as the 3.3V + 1V means we're already above 4.2V of the charged cell. The ASM1117 works well with 5V though, so boosting the voltage might seem feasible. [PDF]

Let's just say you want 600mA from the 5V source you've just boosted, or 3W. With a charged battery (4.2V) and let's say a perfect, lossless converter you would draw current at 712mA. Looking at a voltage of 3.2V this would mean pulling 938mA.

With two or four servos/motors (stall current needs to be measured), an LED that takes 130mA and an ESP32 with Camera coming in at 180mA - this setup can brownout quickly.

With two cells I hope to be able to power the servos at 6V. I want to later verify, that a 2s cell at 450mAh should hold up longer than a single cell battery at 900mAh. 


Xasin wrote 06/24/2021 at 08:11 point

Why even bother with LDOs at high input voltages like this?
Buck modules are becoming quite cheap, TI recently rolled out a tiny 3A module that can be soldered onto a PCB, and they have much better voltage ranges.
I wish Buck-Boost converters would be a bit easier to get too, that would let you use a single cell quite effectively here, but the ICs for those are already quite easy to use too.

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davedarko wrote 06/24/2021 at 08:52 point

it's on the ESP32 CAM board, I'm just using what's given here

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morgan wrote 06/23/2021 at 16:44 point

I've switched exclusively to the AP2112K-3.3 for my LDO of choice. Faster rise times than most *1117 regulators (slow rise (settle?) times cause programming issues with the ESP32) and LESS than 400mV voltage drop @ 600mA.

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davedarko wrote 06/24/2021 at 08:53 point

yeah that's my goto for ESP boards too, I "got inspired" by looking at adafruit boards :D The LDO is on the ESP32 CAM board, so I'm just using what's given here

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