Convert a 5 Volts NANO Breakout Board to 3.3 Volts.

The Arduino UNO and NANO where the pioneers of easy Microcontroller programming.

There are some cheep shields/breakout boards for the Arduino NANO/UNO on the web.

But they are for the 5 Volts versions.

With newer Microcontroller becoming cheaper and better, these Microcontroller are more often of the 3.3 Volts variety.

I am working on a project that is going to use the Arduino NANO 33 IoT.
This newer NANO is 3.3 Volts.

So: This instructable is on how I converted a cheep popular 5 Volts Arduino NANO Breakout Board to 3.3 Volts.

There are many types of the same board.

I thought there was two types; Blue or Red, but when I looked on the web to Identify the one I have, I found many to chose from. Even the Stock Pictures people use to show the versions they are selling are sometimes mixed up.
There are slight differences between them all. The tracks on the board are routed differently.
I believe the circuitry is the same. Well it has to be, for it to work.
In this Instructable I will be converting a Blue Board I have.
If you have a different version, I will try to help if you send photos of your own.
I will try to write the instructable so you may be able to use some initiative for different versions.
What it means is: The tracks that need to be cut may not be in the same place as on my board.

Warning!

5 Volts will damage a 3.3 Volts Microcontroller.

Care and checks should be made to ensure that the 5 Volts Rails are Isolated.
If when checking you find an issue, don't fit a 3.3 Volt device to the board.

There will be two versions of conversion:

Basic. This will change the Broken Out 'V' Pins (5v) to 3.3 Volts. Also the two power pins for Serial and I2C Headers.
Same as above, but I will swop-out the onboard 3.3 volts regulator for a Buck.

The reason for the Buck version is; I have a project that will be using 24 Volts, the Arduino NANO 33 IoT can only have a maximum Voltage supply of 21 Volts.

Those that don't use a supply voltage greater than 21 Volts will not need the second version.
As I am doing it I may as well include it.

Supplies

One NANO Breakout Board.

This is the Board that I am modifying.

Some Insulated Cable.

Not much is required.

One Mini Step Down Power Module Buck Converter. Optional, if doing 2nd version.

I am using a HW-613.
You can change this to what you want that has an output of 3.3 Volts.
I recommend using one that has a fixed 3.3 Volts output, so that it does not get altered by mistake.

Step 1: Isolating the 5 Volts Rails

This is a very important step.

If 5 Volts gets to a pin of a 3.3 volts device, damage will occur.

The shield that I am modifying has pinouts for both the NANO and the UNO.

Both the NANO and the UNO have a 5V pins.
These are the pins I have red arrows pointing to.
It is these pins we need to isolate from the rail pins and Serial/I2C header pins.
I have marked the rail pins and Serial/I2C header pins yellow.

In the image I have high lighted the 5V tracks on my board.

Luckily on my board, both the tracks that needed cutting where on the bottom side of the board.
I have cut them at the red crosses.
The Track I have shown going to the 3.3 volts Regulator on the top side of the board should remain, the NANO 5V pin needs to remain connected to pin 3 of the 3.3 volts Regulator.
You need to follow all other tracks from both 5V pins and isolate them from all the rail pins I have marked yellow.
If possible leave all the yellow marked pins connected to each other.
Don't worry if some of the yellow pins get isolated from each other, this can be fixed later.
The important bit is that the pins marked yellow are not connected to two 5V pins.

I used a small diamond rotary cutting disc to cut through the relevant tracks.

Important

Check and check again.

Using a continuity tester, check between each 5V pin marked with arrows and all the yellow pins, to make sure there is NO continuity.
All yellow marked pins should be isolated from the two 5V pins.

Step 2: Connecting 3.3 Volts

Connecting up the 3.3 Volts to the rail Pins is the easy part.

All the pins I have marked green should connected to each other.

Start at the Green Arrow 3V3.
Using insulated wire connect this pin to the lower power (V) rail.
After connecting this wire check with a continuity tester to find any pins that are not connected to 3V3 pin.
If there are some of the pins not connected to pin 3V3, attach another insulated cable to it and attach the other end of the cable to the closest pin that is connected to pin 3V3.
Repeat if necessary until all the pins highlighted green are connected to each other.

That's it for the basic version.

Step 3: The Original 3V3 Rail Does Not Work?

The above image now shows the path of power after conversion.

Green from the NANO 3V3.
Yellow from the NANO 5V to the Regulator, from the Regulator to the short 3V3 rail.

The Arduino NANO 33 IoT requires the 5V pin switching on.

For the original 3V3 rail to work, requires that the 3.3 Voltage Regulator to be powered.
The power for the 3.3 Volts Regulator comes from the 5V pin of the Arduino NANO.
This is why the track from the NANO 5V pin to pin 3 on the voltage regulator needed to stay connected.
On an Arduino NANO 33 IoT the 5V pin by default it switched off.
To switch the 5V pin on, a jumper needs bridging with solder on its underside.
The bridge attaches the 5 from the USB supply.

Note!

Because the 5V pin gets its power from the USB supply.

The short 3V3 rail only works when there is power from a USB cable. Providing that the bridge on the NANO has been made.
This is one of the reasons I have done a second part to this Instructable.

Step 4: Swop Out the Regulator [Removal]

For most people, what we have done so far will be enough for most projects.

If not all pins on a project are used or if the devices attached to the NANO do not require power, the three pins of the short 3V3 rail may not be needed.
The voltage regulator on the Arduino NANO IoT is capable of 600mA for "User Applications". I think that is on the conservative side, but that what it say in the Arduino documents.

The main reason I am swooping out the current 3.3 voltage regulator on the Shield is:

The Arduino MAMO 33 IoT VIN (Voltage In) goes to an MPM3610, this voltage regulator can only accept a maximum of 21 Volts.
The project I am building is powered by 24 Volts. This will be too much for the Arduino NANO 33 IoT.
I will be fitting a HW-613 DC To DC Buck Converter Module, this can handle a little more voltage.
The HW-613 uses an MP2315 which can have a max 24 Volts input and handle 3 Amps of current.
The HW-613 also has solder jumpers to set fixed output voltages.

To change the Voltage Regulator we first need to remove the on on the Shield.

The is also the Protection Diode that needs removing.
It's not an easy job to remove a SMD, so I have done a video of the way I do it.
There are other ways to remove SMDs, using a soldering iron. You may want to do a search on the web if you don't have the tools I have.

Step 5: Swop Out the Regulator [HW-613]

I was going to glue the HW-613 Buck to the board where the Voltage Regulator was and drill a large hole through to the back of the PCB for the cables to pass through, but not all boards will have an area where this can be done.

So I will glue the HW-613 Buck to the back of the board.
I will be using hot glue so that it will also act as an insulator if needed.

First we need to prepare the HW-613 for 3.3 Volts.

On the back there is a tiny track that needs cutting between the solder points of the ADJ bridge. The HW-613 comes with the ADJ bridged by default.
Then the Bridge for the 3.3V needs to be bridged with solder.

Only three cables need to be soldered to the HW-613.

The EN is not used. By default this is held HIGH with a 200k resistor on the board.
Should you for some reason want to turn off power the the Breakout Pins, you could fit a switch to this terminal that pulls it to GND.
The terminals we will be using are IN+, GND and VO+.

The Buck can handle 3 Amps, so use appropriate sized cable.

At least 24 AWG (0.5106 mm dia.) should be OK.

As we have removed the original Voltage Regulator from the shield.

The short 3 pin 3V3 rail needs connecting to the V pins.
I have put a small link from the 3V3 rail to the nearest V pin.

The HW-613 connections are as follows.

The VO+ is connected to the NANO pin 3V3.
The GND I have connected to the GND pin of the barrel jack socket.
The IN+ is connected to the power pin of the barrel jack socket.

Step 6: Check and Check Again

Before plugging in your 3 volt NANO.

Plug in your power to the shield and check the voltage Between GND and Power Pins.
With the power plugged in the power LED should be lit.
All the Power pins should read 3.3 Volts.

In the image of my shield:

The black pins are GND.
The red and blue pins are power (3.3v).
You may want to black out the 5 where it say 5V on the serial and I2C headers. As these are now 3.3 Volts.