ESP8266 Community Forum

- Sun Jul 01, 2018 6:20 am #76755 I would use the 5V adapter to feed the board as that keeps the dissipation in the 3.3V regulator fairly low as that then only has to drop 1.7V. With a 9V source it is dropping 5.7V and could be heating up quite a bit.

It would also then be the best source for the relay (5V) power direct without going through the regulator. That minimises potential for spikes and the 470uF 3.3V capacitor should then be Ok.

- Sun Jul 01, 2018 7:44 am #76757

... I think I should upgrade it to a HT7833, which can provide 500mA.

It can supply 500mA as long as it is within the power dissipation capability. For the SOT23-5 package 0.2W and for the SOT89 package 0.5W.

I usually use a simple power adapter, like this , but also sometimes use a 9V one. I would rather not rely on the power supply directly.

Using the regulator to supply the relay when powering the board from 9V will exceed the power dissipation capability of the regulator. Also the regulator has a maximum rating of 8 volts.

Only use a 5 volt input supply and use that to power the relay directly. Don't use the regulator to power the relay.