ESP8266 Community Forum

- Thu Mar 16, 2017 11:08 am #63791 My test was with 10k (0.7V). The 3.3k suggested gives 0.27V well below any possible turn on of BJT.

1K is also fine but increases load on the pin when set to output mode and driven high (3mA). Not a problem but just increases current drawn a bit.

- Thu Mar 16, 2017 9:43 pm #63822

My test was with 10k (0.7V). The 3.3k suggested gives 0.27V well below any possible turn on of BJT.

1K is also fine but increases load on the pin when set to output mode and driven high (3mA). Not a problem but just increases current drawn a bit.

cool. so I will change the resistor to 3.3k as shown in below schematic and report the findings tonight.

- Fri Mar 17, 2017 6:24 am #63834 You have to put a resistor between the base of the transistor and the 3.3k resistor. Otherwise there is no current limiting when the port pin is driven high. Using a beta of 20 you would need a 510 Ohm resistor for that coil current. That transistor is operating on the edge of it's specified current rating. It will work but I would prefer to use a higher rated part.

- Sat Mar 18, 2017 4:50 am #63882 Thanks guys for spending your time here and sharing your knowledge. I learnt a lot from your comments and advises. unfortunately this did not work for me. I spent about 10 days to solve this issue with no luck. I gave up and decided to move on to other part of my project.