- Sat Mar 17, 2018 2:01 pm
#74674
At work I have designed a power supply for the Raspberry Pi that has a backup lithium battery. Higher power than the what is needed for the ESP8266 but we only use it to allow for a clean shutdown rather than providing continuous power. It is used in a control system that switches AC power to motors and actuators. If the power fails then we don't have power for those devices so we just perform a clean shutdown that takes about two minutes. From my testing we can run for an hour on the 18650 battery.
rudy wrote:It is a step up (boost) converter. I thought you were going to be using batteries as a backup supply to the AC powered 5 volt supply. I thought you wanted this converter to make the battery voltage higher. If you want a converter to take 5 volts and produce 3.3 volts then this is not the right converter.
Normally the power source (before conversion) will be higher than the required voltage (called a buck converter), or lower than the required voltage (called a boost converter. There are some chips that are designed to allow for a lower or a higher input voltage compared to the desired output (called buck-boost). They are more complicated.
http://www.learnabout-electronics.org/PSU/psu33.php
I have taken a simpler approach on some of my projects. Because I wanted 5 volts for a character LCD, or other devices, I used a boost regulator to take the power from a lithium 18650 battery to generate the 5 volts, then for the 3.3 volts required by the ESP8266 I used a linear regulator.
This is not a efficient use of power but it is sufficient for much of my needs. I have a USB to lithium battery charger to charge the battery and it also powers the device when I need it to run continuously.
I have been using this at work as a data logger for the last two months.
This is the pair of boards I have used together with a 18650 lithium battery. I remove the large USB connector on the boost converter.
At work I have designed a power supply for the Raspberry Pi that has a backup lithium battery. Higher power than the what is needed for the ESP8266 but we only use it to allow for a clean shutdown rather than providing continuous power. It is used in a control system that switches AC power to motors and actuators. If the power fails then we don't have power for those devices so we just perform a clean shutdown that takes about two minutes. From my testing we can run for an hour on the 18650 battery.
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- Sat Apr 14, 2018 5:50 am
#75364
I think you should use a buck-boost converter. You can use them independently or sometimes they come in one package. First the boost converter takes the (possibly very low) voltage up to something which is enough for proper regulation (at least 1 volt higher than you need, a few more could be smart and also take care to choose it such that the input can never become as high by itself) and then the buck convert creates a voltage suitable for operation of your ESP8266.
Advantages of this approach:
- will always supply enough current (as long as the source can deliver it, of course), as buck and boost converter generaly can supply up to 3 A)
- considerably less wasteful, as these converters don't get warm
- no need for cooling
Disadvantage:
- slight switching noise, you may want to consider to have the buck converter set to 5V and then add a classic lineair converter to go to 3.3 V to remove the switching noise, but this adds power dissipation
Advantages of this approach:
- will always supply enough current (as long as the source can deliver it, of course), as buck and boost converter generaly can supply up to 3 A)
- considerably less wasteful, as these converters don't get warm
- no need for cooling
Disadvantage:
- slight switching noise, you may want to consider to have the buck converter set to 5V and then add a classic lineair converter to go to 3.3 V to remove the switching noise, but this adds power dissipation
