Re: Mod proposal to PHSNA

William Kimber

Hi Ignacio,

Two suggestions:

One:  Why use analogue pin unless you wish to measure it?  Why not a digital pin that is pulled high with a resistive divider.  Also solves problem of noise in ADC conversions.

Two: The limit of a USB port is 500mA. Some ports (laptops) cannot even manage that.  Don't forget that for 100mA of 12v DC it will take nearly 300mA of 5v. 



On 12/07/2016 11:54 AM, EB4APL eb4apl@... [PHSNA] wrote:


Several times that I started to use my PHSNA I got a totally flat sweep
graph. It was caused by forgetting to connect the 12 V supply, and since
the Arduino is powered by the USB connection, the program does not
detect that the Power Detector and the DDS modules are unpowered.
An easy modification is to connect any of the free analog inputs of the
Arduino to the 12 V rail using a resistive divider, and modifying the
PHSNA windows program to check the 12 v presence as part of the
initialization routine.
But later I thought that using a DC/DC converter powered by the +5 V
rail to obtain 12 V is a more convenient way, so I'm planning to install
one of these cheap Chinese converters ( less than $1) and see if the 5 V
regulator in the Arduino can cope with the needed current. Maybe it will
need some extra filtering in the 12 V bus but it seems quite feasible.
I'll inform about the results when I finish my tests.

Ignacio, EB4APL

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