# 9V Battery to 2.1mm for Arduino Uno. 9v battery arduino

## Follow me down the optimization rabbit hole

I optimize software for a living. This blog is to share some personal projects which others may find interesting.

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### The Premise

So, you’ve created an Arduino project and you want to power it with batteries to take it on the road. Your board’s components are designed to run on 5 Volts and you know you can’t feed 9V directly into the Vcc of a 5V board because it will damage it. Arduino has you covered. the pin marked RAW is for that purpose and according to the documentation, you can feed it between 6 and 12V and it will regulate that voltage down to the 5V needed by the board. Perfect, right? Well, not quite.

### Voltage Regulation

There are 2 main ways to regulate (aka control) the voltage. A linear regulator allows you to supply a higher voltage than desired (in our case 9V) and get a stable, lower voltage as output. It essentially does this by generating heat from the excess energy. Let’s say your board uses 100mA @5V while executing your code. If you’re powering it from a 9V battery through a linear regulator, then you’re creating 4V x 100mA = 400mW of waste heat (9V. 5V = 4V). If you measure the current coming out of your 9V battery, it will be very close to 100mA, so 9V @ 100mA is going into the regulator and 5V @ 100mA is coming out. The means that the linear regulator effectively has an energy efficiency of 56% in this case. For many many years, the 78xx series of linear regulators is what you would use for cases like this:

Aside from the simplicity, there isn’t much to like about linear regulators. When running on battery power, you’re throwing away a large percentage of your battery’s energy when you regulate the output this way. In circuits that use a lot of current, heat becomes a major concern too.

The older Arduino boards have a linear regulator built in to make it easier to power them from various energy sources. The assumption is usually that you’ll be running from a wall wart (A/C power brick) so wasted energy isn’t much of a concern and that you’ll be running a small current through your circuit, so waste heat isn’t a concern either.

If you’re using a 9V alkaline battery that has a typical energy capacity of 500mAh and you connect it to the Arduino’s linear regulator.

In effect, instead of having a 4.5Wh battery, you have a 2.5Wh battery because the rest of the energy is given off as heat.

Buck (or step down) converters are another way to convert a high voltage source to a lower voltage. Buck converters are a more complex circuit that relies on an oscillator and inductor (coil) to change the voltage. The advantage of the buck converter is that it doesn’t waste nearly as much energy as a linear regulator. Here are the efficiency curves for a typical buck converter:

With 5V output at low current, it approaches 97% efficiency. That means that your 9V battery could potentially provide closer to 4.5Wh of energy to your circuit instead of the 2.5Wh you get with the linear regulator. Electronut Labs sells a convenient buck converter specifically designed for easy use with 9V batteries:

What about going in the other direction? This is the option that’s usually not mentioned in Arduino project articles. It’s also possible to boost the voltage from a lower voltage to a higher voltage. DC-DC boost converters work similarly to buck converters and use a high frequency oscillator and a coil to generate a higher voltage. They also have typical efficiencies greater than 85%. This frees you to use other power sources such as a single AA battery. An Alkaline AA battery typically has a capacity of around 2500mAh. At 1.5V, this translates to about 3.75Wh of energy. Less total energy than a 9V battery, but used efficiently, it can save space and cost compared to a 9V. If we boost 1.5V to 5V and assume that the boost converter has an efficiency of 90%, we should be able to squeeze about 3.375Wh of energy out of it. Here’s a typical DC-DC boost converter sold by various vendors in China for 0.45-1.00 each:

I like to use these in my projects because they’re tiny and inexpensive. They operate down to about 0.8V as input and the output is clean enough (low noise) to use in most microcontroller projects.

### Power Down

The original set of Arduino boards were all based on AVR microcontrollers and all set to run at 5V. This made sense at the time because the AVR MCU can operate on any voltage between 1.8V and 5.5V, but at the higher voltages, the clock can run at up to 20Mhz (see chart below):

The reality is that your project probably doesn’t need the MCU to run at 20Mhz. If you’re reading a few sensors and updating a display, you could accomplish the same work at a lower clock rate. Another reason is that the amount of energy used by the MCU and peripherals does not perfectly follow a linear scale. Even so, you can potentially accomplish the same amount of work running at 8Mhz and 3.3V as you could at 16Mhz and 5V. Running the CPU slower or at a lower voltage uses less energy.

A lot of newer MCUs in the Arduino lineup operate at 3.3v (e.g. ARM Cortex-M MCUs) and so do many add-on boards, so it makes a lot of sense to run your project at 3.3v. Without having to know too much about AVR fuses and hardware, it’s possible to run a board designed for 5V and 16Mhz at 3.3V and 8Mhz with a simple trick in software. The main CPU clock divider can be set in software. We can use this to cause a 16Mhz part to run at 8Mhz so that it can run reliably at 3.3V. The clock prescaler is normally set to 1 on Arduino boards. By setting it to 2, the CPU will run at a more stable 8Mhz:

Now with this new information, let’s look at cost and battery life of our original 5V project running on a 9V battery versus our new idea of running it at 3.3V from a single AA battery. For the cost, I’m making the assumption of buying a 4-pack of each battery type (Duracell) from Amazon.com.

## V Battery to 2.1mm for Arduino Uno

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The 9v Battery Snap Connector with DC Jack with Battery Connector Cap is widely used for project purposes. The 9V Battery Snap Connector with Power Plug provides the ability to conveniently use a 9V battery to power many common boards and modules such as the popular Arduino and compatible microcontrollers.

This plug is a very common barrel type with an outside diameter of 5.5mm and an inside diameter of 2.1mm. The center is positive. Featured By RoboticsBD.

Product Images are shown for illustrative purposes only and may differ from the actual product.

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### Features :

• Excellent Material.
• Fine workmanship.
• It is an environmental 9V battery buckle.
• T- fonts, with red and black connecting lines.
• Save power and protect the environment.
• Good electrical conductivity and comfortable sense of touch.

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 General Specification Supply voltage (V) 9 DC jack Size (mm) 2.1 Length of Cable (cm) 10 Length (mm) 160 Width (mm) 26 Height (mm) 9 Weight (gm) 7 Cable Length (cm) 10 Shipment Weight 0.01 kg Shipment Dimensions 12 × 8 × 2.5 cm

Please allow 5% measuring deviation due to manual measurement.

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### Package Includes :

1 x 9V Battery to 2.1mm for Arduino Uno

### What is the price of 9V Battery to 2.1mm for Arduino Uno in Bangladesh?

The latest price of 9V Battery to 2.1mm for Arduino Uno in Bangladesh is BDT 22 You can buy the 9V Battery to 2.1mm for Arduino Uno at best price from our RoboticsBD or visit RoboticsBD.

Please note that the product information provided on our website may not be entirely accurate as it is collected from various sources on the web. While we strive to provide the most up-to-date information possible, we cannot guarantee its accuracy. We recommend that you always read the product labels, warnings, and directions before using any product

Product Images are shown for illustrative purposes only and may differ from the actual product.

## Battery Powering Arduino Uno

How to battery power an Arduino Uno. The video that follows shows how to make up a cable to connect a 9V battery to an Arduino Uno. A 2.1mm barrel connector is soldered to a battery clip with the positive (red) wire connected to the center of the barrel connector. This type of battery connector is also available already assembled.

This is probably the cheapest way to battery power an Arduino Uno, but has some disadvantages. Continue reading this article for an explanation and alternate methods that can be used to battery power an Arduino Uno.

The pre-loaded blink program starts flashing the on-board LED on and off after the battery is plugged into the Arduino.

A small 9V battery is not practical for powering an Arduino Uno for a long time. This type of battery is fine for intermittent use as well as for use during development and experimentation. To power an Arduino Uno for longer periods of time, a bigger battery is needed.

## How to Battery Power an Arduino Uno

Below are a few different ideas on how to battery power an Arduino Uno.

### Small 9V Battery for Powering an Arduino Uno

As already discussed above, small 9V batteries do not last long when powering an Arduino Uno board. Rechargeable batteries are an option.

The voltage of the battery will be about 9V if six 1.5V cells are used in the battery holder. If rechargeable cells are used, the battery will produce about 7.2V.

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### 12V Sealed Gel Battery

An alternative to using a 9V battery as shown above is to use a 12V sealed gel battery. This type of battery can be connected to a trickle charger or solar charge system.

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### Battery Voltage and Charging

It is important to note that when using a fully charged 12V lead acid gel battery, the output voltage is actually 13.8V. When the battery is charged, either using a trickle charger or solar charge controller, the charge voltage can be up to 14V or slightly higher. If the Arduino Uno is connected to the battery when the charger is also connected, the Arduino Uno then receives the full charge voltage. This voltage is above the recommended input voltage range of 7V to 12V, which means the Arduino will tend to run hot.

### Keeping the Input Voltage in Range

A solution to keep the input voltage to the Arduino lower is to use a 9V switched mode regulator between the 12V battery and the Arduino Uno.

## Follow me down the optimization rabbit hole

I optimize software for a living. This blog is to share some personal projects which others may find interesting.

• Email
• Other Apps

### The Premise

So, you’ve created an Arduino project and you want to power it with batteries to take it on the road. Your board’s components are designed to run on 5 Volts and you know you can’t feed 9V directly into the Vcc of a 5V board because it will damage it. Arduino has you covered. the pin marked RAW is for that purpose and according to the documentation, you can feed it between 6 and 12V and it will regulate that voltage down to the 5V needed by the board. Perfect, right? Well, not quite.

### Voltage Regulation

There are 2 main ways to regulate (aka control) the voltage. A linear regulator allows you to supply a higher voltage than desired (in our case 9V) and get a stable, lower voltage as output. It essentially does this by generating heat from the excess energy. Let’s say your board uses 100mA @5V while executing your code. If you’re powering it from a 9V battery through a linear regulator, then you’re creating 4V x 100mA = 400mW of waste heat (9V. 5V = 4V). If you measure the current coming out of your 9V battery, it will be very close to 100mA, so 9V @ 100mA is going into the regulator and 5V @ 100mA is coming out. The means that the linear regulator effectively has an energy efficiency of 56% in this case. For many many years, the 78xx series of linear regulators is what you would use for cases like this:

Aside from the simplicity, there isn’t much to like about linear regulators. When running on battery power, you’re throwing away a large percentage of your battery’s energy when you regulate the output this way. In circuits that use a lot of current, heat becomes a major concern too.

The older Arduino boards have a linear regulator built in to make it easier to power them from various energy sources. The assumption is usually that you’ll be running from a wall wart (A/C power brick) so wasted energy isn’t much of a concern and that you’ll be running a small current through your circuit, so waste heat isn’t a concern either.

If you’re using a 9V alkaline battery that has a typical energy capacity of 500mAh and you connect it to the Arduino’s linear regulator.

In effect, instead of having a 4.5Wh battery, you have a 2.5Wh battery because the rest of the energy is given off as heat.

Buck (or step down) converters are another way to convert a high voltage source to a lower voltage. Buck converters are a more complex circuit that relies on an oscillator and inductor (coil) to change the voltage. The advantage of the buck converter is that it doesn’t waste nearly as much energy as a linear regulator. Here are the efficiency curves for a typical buck converter:

With 5V output at low current, it approaches 97% efficiency. That means that your 9V battery could potentially provide closer to 4.5Wh of energy to your circuit instead of the 2.5Wh you get with the linear regulator. Electronut Labs sells a convenient buck converter specifically designed for easy use with 9V batteries:

What about going in the other direction? This is the option that’s usually not mentioned in Arduino project articles. It’s also possible to boost the voltage from a lower voltage to a higher voltage. DC-DC boost converters work similarly to buck converters and use a high frequency oscillator and a coil to generate a higher voltage. They also have typical efficiencies greater than 85%. This frees you to use other power sources such as a single AA battery. An Alkaline AA battery typically has a capacity of around 2500mAh. At 1.5V, this translates to about 3.75Wh of energy. Less total energy than a 9V battery, but used efficiently, it can save space and cost compared to a 9V. If we boost 1.5V to 5V and assume that the boost converter has an efficiency of 90%, we should be able to squeeze about 3.375Wh of energy out of it. Here’s a typical DC-DC boost converter sold by various vendors in China for 0.45-1.00 each:

I like to use these in my projects because they’re tiny and inexpensive. They operate down to about 0.8V as input and the output is clean enough (low noise) to use in most microcontroller projects.

### Power Down

The original set of Arduino boards were all based on AVR microcontrollers and all set to run at 5V. This made sense at the time because the AVR MCU can operate on any voltage between 1.8V and 5.5V, but at the higher voltages, the clock can run at up to 20Mhz (see chart below):

The reality is that your project probably doesn’t need the MCU to run at 20Mhz. If you’re reading a few sensors and updating a display, you could accomplish the same work at a lower clock rate. Another reason is that the amount of energy used by the MCU and peripherals does not perfectly follow a linear scale. Even so, you can potentially accomplish the same amount of work running at 8Mhz and 3.3V as you could at 16Mhz and 5V. Running the CPU slower or at a lower voltage uses less energy.

A lot of newer MCUs in the Arduino lineup operate at 3.3v (e.g. ARM Cortex-M MCUs) and so do many add-on boards, so it makes a lot of sense to run your project at 3.3v. Without having to know too much about AVR fuses and hardware, it’s possible to run a board designed for 5V and 16Mhz at 3.3V and 8Mhz with a simple trick in software. The main CPU clock divider can be set in software. We can use this to cause a 16Mhz part to run at 8Mhz so that it can run reliably at 3.3V. The clock prescaler is normally set to 1 on Arduino boards. By setting it to 2, the CPU will run at a more stable 8Mhz:

Now with this new information, let’s look at cost and battery life of our original 5V project running on a 9V battery versus our new idea of running it at 3.3V from a single AA battery. For the cost, I’m making the assumption of buying a 4-pack of each battery type (Duracell) from Amazon.com.