ESP8266 Community Forum

martinayotte wrote:

rudy wrote:I don't know why you are getting those transitions during the high time.

It is know that GPIO0 produce some clock output during reset, it cannot be avoided :
https://bbs.espressif.com/viewtopic.php?t=2101#p6636

Ok this explains the signal at boot, I'm glad it is not an issue with my circuit.
I will attempt to add a low pass filter to prevent the clock output from being sent to the darlington transistor, I this should solve the problem. I will post once I've tried it. Thank you.

Rudy, could you please help me understand your suggestion? I was a bit confused with the terminology, where would the GPIO and the Darlington transistor from my circuit connect to the circuit you provided?
Thanks!

Apologies it took me sometime to write back, I did not have time to play around with this until now.
Rudy, I researched your suggestion and ended up understanding what you meant, I just didn't have the background to get it the first time.
I tested both the NPN and PNP circuits and both worked, and I understand why the PNP is preferred in this case.
I added a capacitor after the collector-resistor on the PNP to create a low pass filter, since the 3.3V clock output was still operating the solenoid. The addition of the capacitor solves this issue.
Below I have the final schematic of the circuit, works well on the breadboard and hopefully will work well once I solder everything onto a perfboard.
Thank you again to both of you for pointing me in the right direction

I'm glad that you got it working. And I am thrilled that you understand how and why it works.