ESP8266 Community Forum

Hello guys..i tried to connect this AC/Dc adapter with 3V selected to power esp but it started to get really hot.so i disconnected it immediately.hope i didn't damage esp.why is that ? how can i use this to power Esps i have ? Thanks..I'm new here.any help would really appreciate..

I rarely will use the output of a adapter to directly power micro-controller circuits. And then only circuits that need +5 volts, never 3.3 volt circuits. And in addition to that I only use switching power supplies, never adapters with a heavy transformer. Switching power supplies use a circuit that tries to provide the stated voltage output. With a non-switching power supply the rated output is a nominal value at the rated output current. Unloaded the output voltage can be more than 50% higher.

If your power supply is heavy for the it's size then it likely does not have a switching power supply, and it is unlikely that the output is regulated.

In any case, it is important to test any power supply you want to use to make sure it provides you with what you expect to get.

I always use a linear regulator to supply the 3.3v I need. There are multiple reasons for this. A linear regulator is more likely to provide you with clean dc power. A linear regulator will typically respond faster to changes in load current. Both increases as well as decreases in load current. Both conditions will result in the output deviating from the desired target. The more stable the supply voltage the more consistent your circuit may operate.

With modules like the ESP8266 the current draw can vary significantly depending on what it is doing. When is starts to transmit it can draw a sudden increase in current and if the power supply can not adequately supply that current instantly there will be a voltage drop of it's output. If the drop gets below 3 volts erratic operation may result. Often this will cause WDT resets.

The regulator that provides the 3.3v dc to the module must as close to the module as possible. The further it is from the module the less likely it is to be able to respond to changes in load current. It is always desirable to have the regulator circuit as close as possible.

But a regulator can only do so much. There also needs to me adequate bypass capacitors on the output of the regulator to supply sudden surges. More capacitance sounds like the preferred solution. Unfortunately it isn't so simple. Larger capacitors have more series inductance and while the capacitor may hold more charge it may not be able to deliver it when faced with a sudden demand. Smaller capacitor are also desired due to their lower inductance. The type of capacitor chosen also make a difference.

I use the ESP12E and ESP12F type modules. Initially I used these on the breakout boards (to 0.1" spaced connector pitch). I soldered in a 3.3 volt regulator rated for 250mA continuous output, with surge capability of 400mA. This should have been adequate but it wasn't. I was getting occasional resets that I found to be related to supply voltage drops. I had first tried to add more capacitance to the adapter board. Both across the +5 volt input and the 3.3 volt output of the regulator. It helped but it wasn't enough. I tried different regulators an I had good enough regulation (minimal voltage dips) with a specific regulator specified for an output of 500mA continuous. Along with the better regulator I use a surface mount 10uF ceramic capacitor on the 3.3 volt line.

Clean power is critical for reliable circuit operation.

On a product I designed about a month ago I used a dc-dc switching power supply to take a regulated 12v and convert it to the 3.3 volts I required for the ESP module. On an alternate population on that board, if I used a ac-dc converter to supply 5v rather than 12v then I have the option of using a 3.3 v linear regulator rather than the switcher.

rudy wrote:I rarely will use the output of a adapter to directly power micro-controller circuits. And then only circuits that need +5 volts, never 3.3 volt circuits. And in addition to that I only use switching power supplies, never adapters with a heavy transformer. Switching power supplies use a circuit that tries to provide the stated voltage output. With a non-switching power supply the rated output is a nominal value at the rated output current. Unloaded the output voltage can be more than 50% higher....

Really Thanks Rudy for your reply.it is full of information and thanks again for taking your valuable time to write it. searching in google i found this circuit based on LD1117.they say it can handle up to 800mA so i think it will do the job.i'm thinking connect this to adapter shown in picture with 5v so i can get 3.3v output.What is your idea ? will it work ? will 10uf and 1uf enough ? Again thanks for your reply rudy..

Instead of the 10uF, I would rather use a 47uF or even a 100uF to satisfy the surges.