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I am facing challenge in powering up NodeMCU from Arduino.

My Arduino is connected with external power supply (12v). From Arduino, I connected 5vpin to NodeMCU VIN and Arduino G to NodeMCU G. However, NodeMCU it is not getting powered up. NodeMCU is only getting powered up with USB. Am I missing anything here?

NodeMCU:

NodeMCU

Connection:

enter image description here

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    \$\begingroup\$ Have you measured that there's actuially 5V at the 5V pin? What if the NodeMCU is drawing so much current that the Uno's regulator can't keep up and drops voltage? (I think it's unlikely but a voltage reading at that pin would make sure). \$\endgroup\$
    – QuickishFM
    Jul 20 at 21:21
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    \$\begingroup\$ What if it powers up, but can't boot due to GPIO pins being strapped incorrectly? Please show the schematics how things are connected. \$\endgroup\$
    – Justme
    Jul 20 at 21:28
  • \$\begingroup\$ Is anything hot? \$\endgroup\$ Jul 20 at 21:30
  • \$\begingroup\$ @QuickishFM , I will check the output voltage and let you know ASAP \$\endgroup\$
    – Kalaivanan
    Jul 21 at 13:07
  • \$\begingroup\$ @Justme added actual connection photography. Please have a look and let me know if anything i need to do \$\endgroup\$
    – Kalaivanan
    Jul 21 at 13:21
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Found the issue.

After I checked the Arduino 5v pin output voltage, I got 0.01V. Then I found it is because of the jumper wires which is not carrying the power at all.

I have around 50+ different jumper wires and everything is not working as it seems to be worst quality and dead after few months

Requesting everyone to buy good quality jumper wires!!

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  • \$\begingroup\$ Just so I understand correctly, there was 5V at the Arduino side (because it was regulated from 12V) but only 0.01V at the NodeMCU? Yes I'd chalk that down to bad quality jumpers UNLESS there was something at the NodeMCU side drastically pulling down the voltage (like a short to ground). If you check the voltage on an open end of the jumper wire with the other end connected to Arduino 5v, is it still 5V? If so, it might not be the end of the world, maybe its so thin and low-quality that any current draw drops it very low. Did you actually solve the issue, by using new jumpers? \$\endgroup\$
    – QuickishFM
    Jul 21 at 22:18
  • \$\begingroup\$ @QuickishFM Both Arduino and NodeMCU is working fine when using new jumpers. Getting 5V output in the Arduino 5V pin. Connecting this to NodeMUC is working fine as expected. Thanks for your help figuring out the issue \$\endgroup\$
    – Kalaivanan
    Jul 22 at 6:14
  • \$\begingroup\$ You're welcome - yes this seems a poor quality jumper issue. I've had my fair share of these in the past so I only use jumpers (known good jumpers) for testing and then for anything permanent or semi-permanent I solder wires or for compaction, make an arduino shield/pi hat PCB. \$\endgroup\$
    – QuickishFM
    Jul 22 at 11:18

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