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Where is the 3.3V regulator on this board? Answered

I need a 3.3V for one of my projects and decided to scavenge one from an old Arduino clone I had lying around. Only problem is I can't figure out where the 3.3V regulator is!! The board has a 3.3v pin and I've also measured a steady 3.3V output using a multimeter but all I can see on the board is a 78M05 and  a diode. I've uploaded a picture of an original Arduino Uno board I have for comparision. The 3.3v regulator on that one is pretty easy to find. Any help in finding the 3.3v regulator will be appreciated.



I traced it , i guess it is implemented in the ftdi ic.

oh im sorry . I too have a similar clone the trace is not visible. I'll search.

just turn the board over and follow the trace from the 3.3v.


3 years ago

Here is a great simple tip that will help you locate stuff on any circuit board:

If you see a component you know about, chances are (very very likely) that similarly related supporting circuitry will be near.

For example: On the arduino boards, the 7805 is right next to the power jack. Everyone knows where the power jack is, and so it is not unusual to find power regulation circuitry and filter capacitors (the large tin can electrolytic caps) nearby. My guess for the 3.3V regulator is the small 5 pin device in the 2nd picture. Although it is a bit small for a LDO regulator, it obviously cannot dissipate much power. It probably does not have to since 5 - 3.3 = and at 100mA, thats only 0.17W.

Another way to locate parts is to follow a trace from a known output, input, or component and see where it leads. You may need to use a multimeter continuity buzzer function to buzz out the trace if it is a multilayer board. I do not think the arduino is multilayer, but there are probably vias and stuff that make it a bit more complicated.

thank you for you reply. What you indicated is the 3.3v regulator on the original UNO board (second image). I'm trying to locate the 3.3v regulator on the clone (first image). All I can see is a 78M05 regulator and an M7 diode. I've included a close up of the board I need to locate the 3.3v regulator.


I cannot see much in the image, it needs to be in better lighting an higher resolution for my to make out anything, also, I would need to see the underside of the board. It is possible that there is no 3v3 regulator on the board, it may be integrated into another chip, like the FTDI chip, although I would not think that that would be the case.

I would try following the trace from the 3v3 pin and see where it leads. Is there actually 3.3V on that pin when connected to power? That being a clone board, possibly a cheap knockoff, it might not have any regulator on that pin, and thus no voltage.

So you want to pull a 3.3V reg off the FIRST board ?

Correct. I want to remove the 3.3V regulator off the Clone..I've just provided the picture of the original UNO for reference.

I am afraid on the clone the 3.3V regulator is included in the big chip next to the USB connector.

At least this was the case with my cheap clone and yours looks quite similar.

If you need more power on the 3.3V line it would be easier to cut the connection on the output pin and to add a dedicated 3.3V regulator either from the 5V regulator or directly from the power supply.

To the left of the IC mount should be enoug empty space to glue the components on top of the circuit board.

You're right I looked up the pin out of the Ft232 and it has a 3.3v OUT pin...I checked continuity with the multimeter and it checks out. Thanks !

Thought it might be the case, so simply cut the connection and hardwire a new regulator to the output pin of the Arduino.
I guess that is what you want?

More amps on the 3.3V output?

No, I had a board running a NRF24L01 module which needs a 3.3v supply. Since I'm powering the board with a 1S lipo I needed a low drop-out regulator and also wanted a small footprint. All I had on hand was a LM1117 in TO220 package so I figured I'd scavenge one off from the clone. Guess I'll have to buy one now. :p


3 years ago

Left side next to the power jack. The chip with three pins on the roght side and one pin on the left

What you think is the regulator is in fact a BC948 transistor.

The 3.3V come from the LP29B5.

For more detailed info simply check the schematics and Eagle layouts on the Arduino homepage.

Look at teh 3.3V pin and follow the trace back to the components it's attached too. The first 3 lead component you find it hits will be the regulator. Chances are it's that small component to the right of the power connector and above the capacitors. Cause the larger on above the power connector is most likely the 5V regulator.