Main Voltage behaviour


I’m trying to emulate a USB supply and hoping to get 5V but Main Voltage is maxed at 4.2V.

I have:
Main V: 4.2V Main I: ~20mA VBUS:5.16V VDC:10.8V (!! my ACDC is 9V nominal)

Main Current>Auto Range is unchecked.

Also: What’s the purpose of having the auto range tied to the Main Voltage? What’s so special about 4.2V (fully charged 3.7 battery)?

What am I missing? Is something bronken?

Thanks - Ric

Hi Ric and welcome to the forum.
It sounds like your ACDC adapter has higher voltage than 9V.
If Arc detects too high voltage on the DC plug, then it will disconnect this supply and fall back to USB powered. When it is USB powered, then maximum voltage with auto range unchecked is 4.2V.

Check your ACDC adapter voltage is my recommendation.

If your ACDC voltage indeed is 9V, then I propose that you create a case in our case system and I will help you to figure out what the problem is.

Best regards,

Yesindeed! My ACDC was putting out 10V+ but is 9V nominal. I changed to a 9.2V and now it works.

Can you explain the Auto Range function’s relation to Main Voltage?


Hi Ric,

When auto range is activated then Arc can measure the current through a higher resistance shunt resistor. Since we compensate for the burden voltage over the shunt, we need to supply a higher voltage internally. So the limitation in output voltage will then be dependent on if the higher resistor shunt is present or not, therefore a lower maximum voltage when auto range is activated.

Best regards,