Voltage drop on connecting with Arduino Pro Mini

Hello,
Noob here :slight_smile:

I have setup as shown in the attachment 1 - an external device which outputs 4,8V and some small current.

I connect a Arduino Pro mini ( as shown in attachment 2) and the voltage drops to 2.2 V on the output of the external device.

Stuoid question - how I can still connect the Arduino Pro Mini without using another power source?
Any ideas what I can use so Arduino Pro Mini runs only from that external device ? Capacitors?

Thanks a lot for any tips

What, exactly, is this "third party controller" and how much is "a small current"?

It is a Logicdata controller but don't know exactly the model.... The current I measured was around 100mA

If that's a 5V "signal" it can't be used to power anything. It has to be 5V power, and of course, it has to be capable of supplying the required current.

For example, you can power a 2nd Arduino from the Arduino's 5V pin, but you can't power the 2nd Arduino from an I/O pin.

In any case, you are apparently pulling too much current from your controller and there is a possibility of damaging it!

It is a Logicdata controller

Of course, how silly of me. :blush:

edgemoron: Of course, how silly of me. :blush:

I am sorry, last night I didn't know the exact model. Here is the exact one: http://www.logicdata.net/blog/product/smart/

with following tech details: http://www.logicdata.net/wp-content/uploads/2017/05/Datasheet_SMART-e_English-Rev1.pdf

Technical Data General Supply voltage EU: 207-253 V / 50-60Hz US: 90-127V / 50-60Hz Nominal voltage EU: 230V / 50 Hz US: 120V / 60Hz Standby power, primary (typical) ≤0,3 W Operating voltage for internal and external electronics and Hall sensors 5VDC ±15% 250mA Operating voltage for internal and external electronics and Hall sensors in standby mode (average) 5VDC ±15% 7mA Precision of Motor current measurement @ 100% Output Voltage and 4-8A ±15% Ambient temperature 0-30°C Relative humidity (for operation) 5-85% (non condensing) Storage and transport temperature -40-85°C Relative humidity (for storage) 5-90% (non condensing) Protection class (with earth terminal) I IP class ≥IP 20 Dimensions (L x B x H) [mm] Tolerances according to DIN ISO 2768-1 c 186 x 100 x 30

You're putting the power into RAW - that goes through a regulator with 1.x V of dropout.

Put the power onto Vcc (and do NOT connect vcc of the serial adapter while it's wired up like that!)