ESP8266 12e - How to connect the TOWER PRO MG90S servo correctly?

Question

Welcome, i am designing a draft measurer for a central heating cooker that allows remote control of the ash cover via wifi, I am using an ESP8266 12e as the control unit. The design includes an AUTO mode, which will adjust the cooker draft based on the temperature (ds18b20 sensor). In addition,...

Anonymous · Accepted Answer

And I think the problem is software, as servos usually accept voltage levels of 3.3V or even 2.5V.
Unfortunately without an oscilloscope it will be very difficult to determine what is wrong here.
Although you can try to use the audio input on your computer. You could feed a waveform to it using a series resistor and capacitor circuit (10k + 100nF) and record the sound with any program (even a windows sound recorder). At least the duration of the pulse could be verified this way.

Anonymous · Accepted Answer

I think it was the ESP that stopped generating a signal.
The signals look fine.
The interval between pulses is 20ms. The pulses are 2ms or a little less (a pulse is one half of the spike, the other half of the spike is the return of the voltage to the DC component).
On the other hand, the problem may be the polarity of the signal, as you can see that it is negative (another thing is that the sound card may invert it, because for the sound it has no meaning).
Perhaps this ESP signal generation code assumes that behind the ESP output there will be a transistor amplifying the signal to 5V (which, by the way, reverses the signal polarity back).
Change gpio.HIGH to gpio.LOW and gpio.LOW to gpio.HIGH in your code and see what changes.

gnato · Answer

Thanks for the answer.

Regarding your way of measuring the wavelength using a resistor and capacitor I have 2 questions:
- is the microphone input enough? I have a laptop without a line input.
- i have drawn out the circuit to make sure it is laid out correctly, can you confirm that it is ok? (there was no jack plug component available, so I added a socket instead)

Anonymous · Answer

More or less something like this.

gnato · Answer

More or less, that is, if I connect such a circuit I won't burn anything?

Anonymous · Answer

There is never any certainty. But the risk of burning is very small.
In the schematic you have a small mistake because you used an electrolytic capacitor.
And you need an ordinary one (ceramic or film).

gnato · Answer

I bought such a capacitor, will it be suitable?

gnato · Answer

The reading came out as follows:

Anonymous · Answer

Well, then something is wrong. And in the voltage reading, and in the frequency.
That is, it is as if both this "oscilloscope" and the output to the servo from the ESP8266 chip are not working.
Maybe something is just not connecting?
Try taking the measurements again and throw them here as a WAV file.

gnato · Answer

I recorded 2 files:
1. alarm.wav - which is the result of calling a piece of code:

Log in, to see the code

2. pwm.wav - which is the result of the code piece:

Log in, to see the code

I think I've managed to capture the correct signal at some point (I've cut out the relevant bits). The only thing that puzzles me is why the signal wasn't recording all the way through. Is it a connection issue, or is it a matter of the esp somehow losing the set signal (which seems rather impossible to me, but as I'm a beginner I could probably be wrong).

Finally, I just wanted to apologise for the fact that my answers are rather long-winded, unfortunately this is dictated by a rather small amount of free time (work, work, work...).

Thank you also for taking an interest in the topic and wanting to help me

Greetings[/code]

gnato · Answer

I swapped as you suggested, however the servo only "buzzed" without any reaction. Nevertheless, I think I managed to solve the problem. Namely, until now I had the servo connected to the power module, while the ESP itself was connected to the arduino, which serves as my programmer.

After connecting the servo to the power supply from the arduino, the whole thing started talking to each other correctly by using the pwm method. Moving on, I switched entirely to the power module for a moment and the communication was also working correctly.

I was not aware that connecting different components to different power supplies could cause this behaviour. I think the topic to close, atom1477 thanks a lot for your interest in the topic and thanks for your help

Anonymous · Answer

It was not the different power supplies that were the problem here. Just probably a failure to connect the masses of the 2 sources.

ESP8266 12e - How to connect the TOWER PRO MG90S servo correctly?

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