ESP8266 Community Forum

- Thu May 30, 2019 7:29 am #82558

Did you use tantalum capacitor?

I used a 68uF tantalum in parallel with a 10uF ceramic at the module.

This was when I started with the esp8266. I had been blaming the crashing on code problems. But at one point I decided to bring the boards to work and check them out on the scope. I found very short duration glitches. I had thought the capacitor should have kept it up but it didn't.

I had wanted to use these as we I had quite a few that had were on a Zigbee radio I designed into a product at work. The regulator was causing unreliable operation so they were replaced with a capacity rated part.

- Thu May 30, 2019 7:39 am #82559

I think one of the reasons why good LDO regulators are popular for LIPO battery projects is that they are simple, cheap and pretty efficient given that the voltage drop wastage from the LIPO regulating down to 3.3V is actually pretty small.

The working range of typical LIPO batteries is from 4.2V down to 3.3V. Raw ESP modules will operate fine at 3.0V so even taking into account drop out voltage of a good LDO you can extract pretty much all of the charge from the cell.

Finding efficient switching regulators with low quiescent is quite difficult and if you add in complexity of buck / boost to run down to the lowest voltage then it gets even harder.

Having got a reasonably efficient regulator, there is more to be gained by optimising the software to spend as much time in deep sleep as possible rather than worrying about a few % in the regulator. That means using the longest sleep time consistent with functionality and minimising the wake time to perform any action. In particular, wake time can be kept low by using techniques like only turning wifi on when needed (e.g. batching up results) and by avoiding dns if possible.

It is obviously important to ensure that any other sources of quiescent current are kept low by paying attention to any biasing circuits and powering down any sensors.

Now if you want to use alkaline cells as well then the first thing to consider is in what configuration. If 1 or 2 then you have no choice but to use a boost regulator. 3 cells would give something comparable to the LIPO range 4.5V down to 3.0V with maybe a bit of charge left at the bottom end. 4 cells is swinging the argument in favour of a decent buck as the wastage through an LDO is becoming significant.

I get good results using the xc6203 in my LIPO projects. Note there are two variations of this chip. I prefer the E variant which does not have the hard current limiter built in so there is less risk with the short duration 400mA spikes the esp8266 sometimes needs (pulse current ratings are up to 600mA). Decent decoupling also helps avoid problems in this area.

Excellent tips!
Thank you!

What decoupling capacitor do you use in your project?

The software part, I'll do as you explained. I'm thinking of a faster form of communication, maybe UDP ...

What technique do you use to cut off power from the sensors? mossfet?

I understand that you prefer the variation without overload protection, but in case of a short circuit or overload that could damage it, it will burn ... Do you have any protection method to avoid this?

I am considering using any of these:
xc6203
HT7833
AP2112
RT9013
SPX3819

I'll study them better to see the pros and cons.

- Thu May 30, 2019 8:08 am #82561

Did you use tantalum capacitor?

I used a 68uF tantalum in parallel with a 10uF ceramic at the module.

This was when I started with the esp8266. I had been blaming the crashing on code problems. But at one point I decided to bring the boards to work and check them out on the scope. I found very short duration glitches. I had thought the capacitor should have kept it up but it didn't.

I had wanted to use these as we I had quite a few that had were on a Zigbee radio I designed into a product at work. The regulator was causing unreliable operation so they were replaced with a capacity rated part.

Got it!
Thank you very much for the information.
I'm using a larger capacitor to avoid this kind of problem.
But as I'm going to change the regulator, I'm evaluating changing the capacitor.
I currently use a tantalum capacitor of 220 uF.
In parallel I use another ceramic capacitor of 10 uF or 100 nF (I can not remember the exact value now)

- Thu May 30, 2019 11:15 am #82564 The 68uF+10uF is what I have been using on my boards. When I was having the problems with that regulator I did try a larger value capacitor since I wanted to stick to that regulator. But a larger capacitor had no effect. The glitch was very narrow and I expected the cap to handle it, but it didn't.

If you do try it, let us know how things went for you.