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I am new to electronics and for my first project, I am using an esp8266 12 e WiFi chip to put together an air sensor web server. My breadboard prototype works but I want to add some other sensors which require 5v. So I need to power the chip at 3.6v and some of the sensors at 5v. I am planning on getting a power adapter plugged into mains and then a buck converter or 2 to get the required voltages. If I get a 9v power adapter, I need 2 buck converters. If I get a 5v power adapter, I only need 1 buck converter. However, I am aware that there are minimum voltage differences between the input and output voltages so am not sure if this will work, given that 5v is kinda close to 3.6v.

I found this pdf which seems to address this question. However my inexperience is making this difficult. Can someone with more experience either 1) tell me if the voltage difference is big enough, or preferably, 2) walk me through the maths in the pdf to arrive at a conclusion?

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    \$\begingroup\$ Why do you think you need 3.6 volts and not a more typical 3.3 volts? \$\endgroup\$ – Chris Stratton Jan 6 at 8:03
  • \$\begingroup\$ People have been saying that it is more stable at 3.6v. \$\endgroup\$ – Chechy Levas Jan 6 at 8:07
  • \$\begingroup\$ But other than solving this specific problem, I want to develop enough of an understanding of the linked pdf to solve the problem generally. \$\endgroup\$ – Chechy Levas Jan 6 at 8:08
  • \$\begingroup\$ If you are new to this, consider a low dropout linear regulator. It is less efficient than a switcher, but a lot easier to get right. They are available in adjustable form as well as fixed. A well chosen one would still have plenty of headroom between a loaded down 5v adapter and a 3.6v output. See the data sheet - the number you want to look for is the "dropout" voltage difference, and you need to look at the number applicable to your peak current. \$\endgroup\$ – Chris Stratton Jan 6 at 8:13
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    \$\begingroup\$ Don't overlook that there are plenty of ESP8266 boards with a USB socket as their power input and published design. \$\endgroup\$ – Chris Stratton Jan 6 at 8:15
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The term you are looking for is dropout voltage, that is the voltage drop between the input and output of a regulator.

The Mini360 modules, like most other buck converters, have a very low dropout voltage and you are safe to use it. I have not found a datasheet of the specific chip used on this modules, but you can be certain that it will work fine from 5V to 3.6V.

I would avoid feeding 3.6V to a ESP8266, as that is its absolute maximum rated voltage is 3.6V, which means that any tiny glitch could blow it up. I would stay on the recommended 3.3V, and put a nice large capacitor to smooth things out.

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