Powering Projects

Once your projects need to get out into their target environment, often you need to replace the power from your PC USB Connection / Other PSUs for a localised supply.

Depending on your board, needs and experience, there are a variety of solutions available...

 

Choosing Batteries

Often you need batteries to power your project, the below helps to identify the useful differences between these:

Battery Type Cell Size Regulator / Charger Simple Capacity Sensing
LiPo 3.3v Charger + Regulator Not available as voltage remains at 3.3v until near end of lifecycle
NiCad / NiMh 1.1 - 1.3v
AA / AAA etc
Regulator  Generally these can be directly sensed by voltage level + divider for remaining capacity estimation.
Lead Acid Variable Charger + Regulator Generally these can be directly sensed by voltage level + divider for remaining capacity estimation.

 

Onboard Power Supply

Some boards come with a built in regulator and DC Jack connector.  This is a convenient way to connect to a power source, which can be a battery. Consult the board information for the voltage range and jack connectos which are applicable.

NOTE - generally these are fixed voltage regulators, and as such require a higher input voltage than their output.  Some boards supply specialised circuitry for LiPo battery connections and charging (e.g. Adafruit Feather) which should be considered seperately.

 

Fixed Regulators

These are the simplest to connect, and require the least components at an effective cost.  These are often buck regulators, so require more power in than they output, with the difference being emitted as heat from the component.  These are low efficiency components as all spare power is simply converted to heat. 

e.g. LM78XX ICs 

NOTE - If choosing a fixed regulator for a project, ensure the heat dissapation is considered, and its relevant wastage is considered.  Consult the component datasheet for more information.

LM78xx Datasheet

Variable Regulators

These require more connections and external components, but allow a variety of output voltages to be set from the same component, and often come at a better price than fixed regulators.  These are often buck regulators, so require more power in than they output, with the difference being emitted as heat from the component.  These are low efficiency components as all spare power is simply converted to heat. 

e.g. LM317T ICs

LM317T Datasheet

Boost Regulators

These allow a lower voltage to be raised to a higher voltage, at a lower amperage, often using a configurable regulator IC.  These can be purchased as pre-built boards, or integrated fully as with the variable approach using some external components, and would allow e.g. an ESP8266 to run from 2 x AA batteries with WiFi.  

NOTE - you often see low amperage LED drivers marketed for this purpose, often using the N11F marked IC.  These will NOT power an ESP8266 from our experiences.

An example of the configurable boost regulator is the LM2623AMM boost regulator, which can be used to reliably run an board such as an ESP8266 from 2 x AA batteries.

LM2623AMM Datasheet

Example Circuit for 2xAA Batteries to 3v3 Output

LM2623AMM Boost Reg Circuit Example

Switching Supply

This is often available either as a small board which can be integrated into your project, or a single package like the regulators above.

These offer a much higher efficiency than the above regulators, so your project can run for longer than using a standard buck regualtor. 

These can also have other features such as buck/boost capability allowing them to operate both above and below the target voltage, making them a good all round solution to support a general toolkit.

LM2575T-3.3 Datasheet