Relais turned on stops ESP8266 and disconnects from Blynk

Dear All

I quite new to this world and have some issues with my project. I have done some research on this community and google, but I haven’t found this problem, which I am not able to solve, in a nutshell:

When I turn on relais Nr2 (D5/GPIO 14) to power a micro water-pump, the pump turns on as expected, but very often (randomly) ESP8266 stops to work and goes offline. Interestingly, this never happens when I turn the Fan on via relais Nr1 (D6/GPIO12).

ESP8266 V3 with WiFi Connection
ESP8266 Protoshield providing 9v-5v-3.3v
Two-Channel Relais Modul 5V
Micro Waterpump 120L/h 2.5-6V
NoiseBlocker BlackSilent Fan 4-12v
Two DS18B20 and one Si7021 sensors

External 9v for ESP8266 Protoshield
External 5v for Water-Pump
ESP8266 Protoshield 5v for Relais Module
ESP8266 Protoshield 9v for Fan
ESP8266 Protoshield 3.3 for Sensors (all separate)

Once turned on, the small water-pump causes some power stability issues within the circuit (due to higher power drain?) impacting ESP8266 and WiFi operation (blue led tops to blink).

Usage of relais Nr1 for water-pump
Change of power-supply
Check of wire connections
Check of pins usage

Thank you in advance for any help and greetings from Switzerland.
Saluti, Andrea

You seem to be saying that the pump has its own independent power supply, and that the relay board also has an independent power supply. Is this correct?

I have once had a situation where a project worked successfully on the bench, but not when it had the load connected to the relay contacts.
The load was a 12v AC door release, and it seems that the noise spikes generated by this were somehow making their way into the control side of the circuit and causing the MCU to reboot. The solution was to put a capacitor across the load terminals of the relay.


Dear Pete

Thank you for your amazing rapidly intervention !!
I need to clarify, since probably I was not very accurate:

  • PUMP: YES, it has its own external power supply running on 5v (however plugged on the same plug)
  • RELAY BOARD: NO, is being sourced by the ESP8266 Protoshield 5v (ESP8266 is snapped on top)

Mmmmh, your experience is very similar with mine. On the bench (using your expression) the relais work perfectly, so with the fan (which I guess is already protected). Just with the water-pump goes on the issue occurs, and I need to reset everything.

Reading some posts in different forums, some use capacitors too (as you described). Now I need to find out the right capacity for the situation and try (…) Let’s see where this ends.

Thank you again and saluti

[Unformatted code removed by moderator]

@tanziandrea please edit your post, using the pencil icon at the bottom, and add triple backticks at the beginning and end of the the code so that it displays correctly.
Triple backticks look like this:


My problem required a 220uf capacitor across the relay contacts.


@tanziandrea you’ve edited your post, but haven’t used the correct characters at the beginning and end of your code, despite me giving you triple backticks to copy/paste.

Please edit your post again, otherwise your unformatted code will be deleted.