hello,

have you noticed this:
If I connect the USB port of the arduino and I do not turn on the 12V power supply, the internal 12v-->5v? voltage regulator switches the 5v to the 12v input. He’s actually walking backwards.
it’s probably related to the design of the regulator,?
Amazing though
Made the test.
cdt

cdt

Gerard,

The internal 5volt regulator for the Nano is supplying the power to just the 5volt parts of the Raduino (or anything else connected to the 5volt rail).? This usually includes the display which is why IF you have a larger than a 3.5" display you should supply it with a separate 5volt source.? The Nano regulator can only supply a little over 500ma.?

The full radio is not being powered, only the Nano, Si5351, and the Display.??

73
Evan
AC9TU

Hi Gerard,

Yes - it even receives weakly!?

I use CAT control and keep the USB connected all the time so I disconnected the +5 from the USB input.? I recently got a powered USB hub that lets you turn the +5 on or off individually on each port.

Dean
KK4DA

Evan,

I agree with you.
Now look my 5v regulation of my Arduino. It's the same that on V5, V6 etc.
The test to do is to connect the USB port of the Arduino to a pc, and do not put power on the Ubitx.
Me, I have the impression that the 5v of the arduino goes up on the "out" of the regulator and therefore gives + 5v on in fact the "in" of it.
A diode should be put at the output of the regulator towards the 5v of the Arduino.
Made? the test to.? ? I'am not crazy.....Lol
Here my Schématic, it's the same on V5, 6!!

So the good modification is:? ?OR MY REGULATOR DON'T WORK ?? NOT SURE!!


Current Schematic:

Dean,
Thank's for your answer
I don’t think that’s gonna solve my sound pb’s.
But I’ll try to change it
cdt

--
Jack, W8TEE

Jack,

It was a quick answer
We can of course compensate the loss due to the diode
There are lots of schematics on the net

Example:






cdt

On Thu, May 13, 2021 at 01:04 PM, Gerard wrote:

It was a quick answer
We can of course compensate the loss due to the diode
There are lots of schematics on the net

Gerard,

I would suggest that you move the diode to the power input of the regulator.? That would also help in dropping the 12volts down by .6olts.? A small help in the power dissipation of the 5volt regulator

I have powered my v5 and v6 ?BITX Raduino without the 12volt supply.? I never noticed any received signal, but it may have been there.

73
Evan
AC9TU

Hi,

If you read the datasheet for the regulator it's warned about there:

8.1.2 Raising the Output Voltage Above the Input Voltage? Because the output of the device does not sink current, forcing the output high can cause damage to internal low current paths... this diode, low current metal, and the regulator are destroyed.

I don't know how much current it can take, or how much current the rig would draw while connected, but a diode might not be a bad idea.? Just to be on the safe side.

73.

Hi?

I have a lot of regards about replacing the 7805 by a switching module. If the 7805 is damaged, little or no output voltage would be present, but if the active switch a switching module is damaged, then the 12V would be connected straight to the 5V rail through the inductor, potentially killing the raduino, and even a computer connected to its USB port. Also, a step-down switching module generates a lot of noise on the 12V rails in the RF range.

Remember: a step-down is constantly "shorting" the input, and a step-up is constantly "shorting" the output.?Unless you use a coupled inductor???uk?design, there is no way to have no RF being generated by a SMPS in one of its rails.

That said, on the other hand, the 7805 needs some kind of protection, as pointed out by Gerard, and I believe it can be as simple as a schottky diode.



Rafael - PU1OWL

开云体育

How about doing what is as done in many Yaesu and Icom transceivers put a 7808 in series with the 7805 that will set the voltage change at 4 volts then 3 volts which will make the regulators run cooler. Also additional protection.

Thanks

Bob, k1wyc

Hi?

I have a lot of regards about replacing the 7805 by a switching module. If the 7805 is damaged, little or no output voltage would be present, but if the active switch a switching module is damaged, then the 12V would be connected straight to the 5V rail through the inductor, potentially killing the raduino, and even a computer connected to its USB port. Also, a step-down switching module generates a lot of noise on the 12V rails in the RF range.

Remember: a step-down is constantly "shorting" the input, and a step-up is constantly "shorting" the output.?Unless you use a coupled inductor???uk?design, there is no way to have no RF being generated by a SMPS in one of its rails.

That said, on the other hand, the 7805 needs some kind of protection, as pointed out by Gerard, and I believe it can be as simple as a schottky diode.



Rafael - PU1OWL

Hello,

What I saw is actually a tough one, but doesn’t interfere with the operation.
Besides I did the test to remove it and put 2 separate power supplies of 5V and 12V, my parasitic noise does not leave.
If you want for low noise regulator mountings, I found regulators based on LT3045. There are many models.
Example:


cdt