LIR 2032 Piggy Back

Other Hardware General Electronics
1

Ive had a lot of problems using SD cards with my ESP32. The only card I can get to work is a 10 year old, unbranded card.

I read about power suply being the issue and when i tested with a multimeter, the voltage was between 3 and 3.3 volts.

As an experiment i tried boosting the system with a LIR 2032 (rechargable) between the voltage out and the ground. It now reads and writes to all my cards. However I have a few questions about this.

  1. is it safe? The battery isn't getting warm, but might it explode.

  2. is this just a short term solution until the LIR 2032 runs down or will it get a trickle charge from the ESP 32 and just ballance out the voltage.

1 and 2 are related because time will tell if it is a long term solution, but I don’t want to leave it unmonitored if the battery may explode.

As you may gather, I'm no electronics boffin. Comments would be welcome, even if it's only to tell me I'm an idiot.

2

Try an electrolytic capacitor across the VCC and GND pins of the SD card reader instead of the 2032 battery.

3

It's not safe

is this just a short term solution until the LIR 2032 runs down or will it get a trickle charge from the ESP 32 and just ballance out the voltage.

It's not a solution at all because it's not safe

4

@iangill
Are you using a module that claims it can work on 3.3 or 5V

5

3.3 Volts.
Has something changed with microSD cards in recent years? My old Sd card works fine but all my new ones fail to mount.
It seams a bit OTT to have to use a separate regulated suply just for an SD card slot.

6

Some cards use more current than others and they can use up to 100mA when writing
Do like @UKHeliBob suggested and put a capacitor across the 3.3V pin and ground close to the card. Try 100uF

7

The capacitor seams to be working.
I had tried that earlier but not right next to the SD pins, just generally across the system. The proximity seams to make the difference.

Thanks chaps.

8

Jim, is it not safe because the amperage will be too high for charging a LIR 2032?

9

It's unsafe for several reasons.

  1. A fully charged battery can have a max voltage of 4.2V. That could damage the ESP and/or SD card.
  2. When you turn off the ESP the battery will feed back to the ESP through the 3.3V connection.
  3. Once the battery voltage drops 3.3V there is nothing to control the current going to the battery, which is not good.

In general, anything you do that does not provide the proper charging profile for a battery should be considered unsafe.

10

Thanks for that. Every day is a learning day.
There is a socket to plug a battery into the Lolin 32 lite which acording to the specs will charge from the USB.
That however goes through a regulating chip.

11

So connect the 100uF capacitor and see if that solves the problem

12

This has proved to be an intermittent fix, sometimes it works and others not.

Whilst there is 3.3v between the voltage out pin and ground, it drops below 3.0v at the SD card.

Can i turn this on it's head? Rather than having the ESP powering the board, can i have a regulated 3.3v supply power the board, and and that power the ESP32 via the voltage out pin and the ground. Is this an appropriate way to power the ESP32?

With 2 sensors and the SD card, i was wondering if the current draw is too much for the card voltage regulator.

13

Probably not but there are many dozens of variations of ESP 32 modules.
Which one do you have?
Are you using a solderless breadboard to connect everything?

14

Its a Wemos Lolin32 Lite.

I am using a solderless breadboard until i get it working and then I'll solder it all to more perminant prototype board.

I asumed that the 3.3v would be feed across the board from the output of the voltage regulator. And the ground would be similar.

15

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