BATC Forum

I have just completed my Pico Tuner which works well. Many thanks to Colin, Mike, Tom et al.

I decided to build my tuner to operate solely from the USB lead. It worked fine like this when plugged into a USB3 port on my PC but it 'upset' my PD4 - dragging the voltage down, I think. That prompted me to measure the current draw from the USB connection, which was 780 - 790mA.

I Googled USB info and found that USB2 ports are supposed to give 500mA and USB3 to give 900mA. (I think a lot of laotops may fall short of this spec.)

My conclusion is that it may be better to power the Pico Tuner from 12v when it is used in a PD4.

73, Russ.

How is the PD4 powered?

The Pi4 is fed by a Chinese 300W buck converter set at 5.1V.

Does the converter drop at all? The PI4 can supply 1.2A from the USB, total from all of them so it should work. Also the voltage dropping isn't a problem for the USB pico as long as it stays above 4V.

Mike

The current drain when powered from USB is higher than recommended. However most computers and laptops seem to be happy with this.

The RP4 is a bit more fussy and may not work, especially if it's also powering other devices. My Portsdown system seems to be OK but it probably varies between systems.

As you say you still have the option of powering it from 12V

Colin G4EML