220/110v input

Hi Guys...

I am new to Arduino, I hope you can help me!

I have an UNO that has a NRF24L01 and a NODEMCU on it also I have 3 POWER HD 20KG servos on it as it is now I am giving the servos power from an external battery and the UNO and NODEMCU are getting power from an 12v 2amp power supply from the 220v wall socket.

What I want to do is to have everything to get power from the 220v wall socket via a power supply and still have a battery in for backup, but I have no clue what resistors and what els to use?

Thank you

For the servos, you would need a 5 to 6V power supply capable of providing three times the servo stall current, which is probably several amperes per servo. Try to find a data sheet or product page listing that stall current.

Probably you can use a voltage divider with 2 or 3 resistors to divide the voltages from the battery and then use them to achieve your desired output voltages. Keep in mind the values of resistors will be responsible for the amperes flowing through.

Ok thanks guys, so you think that the 1 12v 2amp power supply will be enough to power ever thing? Even the 20kg servos?

  1. jremington thinks the power supply won't be enough. I have no idea how large 20kg servo is but he is experienced and probably right.
  2. You CANNOT use voltage divider for such thing, there are special circuits for this. It is quite complicated and likely out of your reach to design and make such circuit yourself. You need either a lot of experimenting and reading or buy suitable power supply. Anyway you need to know voltage and power rating of the servos.

Electrical:
Probably you can use a voltage divider with 2 or 3 resistors to divide the voltages from the battery and then use them to achieve your desired output voltages. Keep in mind the values of resistors will be responsible for the amperes flowing through.

Absolutely definitely you cannot use a voltage divider.

Servos need regulated voltage, 12V will pop them, divide by 2 at zero amps will mean well below 6V at load since a divider doesnt regulate.

The specs of those servos suggest stall current will be of the order of 3A or more.

This means at least a 6V 10A supply is needed, as well as the 12V rail (which sounds like its only
powering microcontrollers and could be 8V or so.

Electrical:
Probably you can use a voltage divider with 2 or 3 resistors to divide the voltages from the battery and then use them to achieve your desired output voltages. Keep in mind the values of resistors will be responsible for the amperes flowing through.

That is complete and utter nonsense and it scares me that someone writing that lists "http://www.basicsofelectricalengineering.com/" as his website.

it scares me that someone writing that lists "http://www.basicsofelectricalengineering.com/" as his website.

Have you taken a look at the website? Mostly Ohm's law calculations, and only 9 followers are listed, so little harm is done.

I was amused by this definition of a diode:

The diode is a two terminal component which allows the flow of AC in one direction and stops it in another direction.

MarkT:
Absolutely definitely you cannot use a voltage divider.

Servos need regulated voltage, 12V will pop them, divide by 2 at zero amps will mean well below 6V at load since a divider doesnt regulate.

The specs of those servos suggest stall current will be of the order of 3A or more.

This means at least a 6V 10A supply is needed, as well as the 12V rail (which sounds like its only
powering microcontrollers and could be 8V or so.

Thanks, Mark, so what will be the optimal solution for the case?

I’d go for an SMPS.

@Electrical: rather than use the report to moderator control, why not use the forum to refute?

jremington:
Have you taken a look at the website? Mostly Ohm's law calculations, and only 9 followers are listed, so little harm is done.

I had a quick look and also was slightly amazed in how many ways you can package Ohm's law and think you something new. Looks like a candidate for the picture next to the dictionary entry for Dunning-Kruger effect :slight_smile:

jremington:
I was amused by this definition of a diode:

That's hilarious :smiley: