I am getting strange and incorrect voltage readings from my projects

Hello all, I have recently been following an online tutorial on how to build an Arduino drone, the flight controller is done. i am building the transmitter (controller) I will include the schematic along with pictures now

The next image is to showcase my poor soldering skills maybe you will look at this and believe that this is the problem, I just want to mention that I am using Draper solder wire, with flux inside and it seems to be very good solder wire I just need practise.

Now returning to my query I have came across a strange problem, upon plugging the 9 volt battery in the red LED on the arduino nano came on, however after switching the switch on the LED I switched the main power switch on and the LED became brighter,(want to quickly mention even with the switch in the off position I was getting the same voltage readings, I desoldering and removed the switch, tested continuity on the switch and it seems okay as it beeps with the switch on, and doesn't when its off)

I measured some points of the circuit with my multimeter, I am suppose to read ~3.3 volts to the NRF24 radio controller and 5volts top the arduino.

However my reading were 1.7v between 5v and GND, 2.7v between Vin and NRF24 gnd, and 3.6v between 5v and NRF24 gnd. very strange how I am getting some voltage but not nearly enough, and to add to this issue, I noticed the LED on the nano quickly dimming before my eyes, until it was completely off, and the voltage reading for each were slightly lower this time, here are my results after 5 and 15 mins(I will will include the before-mentioned values next to these so you guys have an easier time comparing them) :

(I rounded all these to one decimal place)

1.7v between 5v and GND, after 5mins = 1.4v after 15mins = 1v
2.7v between Vin and NRF24 gnd, after 5mins = 2.4v after 15mins = 2v
3.6v between 5v and NRF24 gnd, after 5mins = 1.5v after 15mins = 1v

I noticed after doing this that the point in between Vin and NRF24 gnd were maintaining a similar voltage reading, whilst the points between 5v and NRF24 gnd dropped drastically.

I don't know whether it is something to do with the 10mF capacitor or AMS1117 5.0 DN911 voltage regulator, or whether my awful soldering skills have caused issue such as short circuits, its very difficult to tell as a beginner. This is the first thing I have ever really soldered and its been tough to say the least, any help would be greatly appreciated thank you very much for reading this far!

You have to fix the soldering. I don't know if that is the cause of the problems, but you have to fix it anyway.
Is your soldering iron too hot or too cold ?
For electronics I prefer 0.5mm or 0.7mm solder wire.
Solder with lead is a little easier, but lead-free solder should not be a problem.

Do you have a solder sucker or solder wick ?

It is best to put the NRF24 somewhere else.

This is a basic soldering video:

If you have some money to spend, then buy a solder iron with the heating element in the tip. Sometimes called "direct heating"

my soldering iron doesnt even have a station, I had to 3d print a holder for it, I have no way to tell the temperature, I do have a solder sucker so I can redo the whole thing, im gutted tbh.

Just the NRF24 to start with. You can check the rest with a multimeter and a magnifier.

Please start your strip board ALL over again.
First clean the copper tracks with.
Methylated Spirits.
metal cleaner
until they shine.

Clean the outside of your solder.

The reason the LED came on when you connected the battery with the switch OFF was because you were still powering the 3V3 regulator that would backfeed current to the Nano.
This should fix that problem.

Tom.... :smiley: :+1: :coffee: :australia:
PS, I hope you didn't solder the Nano into the stripboard, solder header sockets into the strip board so you can plug and unplug your controller.


Tom... :smiley: :+1: :coffee: :australia:

Unfortunately I did solder the nano straight on there but I could try to get it off, it will be very tricky as all pins will have to be free at one time.

Thanks for the advice ill post an update here, tonight or tomorrow. why do you think the 3V3 regulator is back feeding current to the nano? I only ask because I like to learn from errors :slightly_smiling_face:

As you are only supplying 3V3 to the NRF, and no power to the Nano, some of that potential appears on the MOSI and MISO, CE etc lines.
This basically provides enough potential to power some of the Nano via the protection diodes that are connected between I/O pins and the 5V of the controller.

Tom... :+1: :coffee: :australia:

Temperature control is essential for soldering electronics, absolutely....

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