I am using a ESP32 as a transmitter circuit for a small project. Essentially the circuit is an ESP32 connected to a pushbutton. As the button is pressed, an IR LED emits a signal that is programmed via Arduino IDE on to the ESP32. I want to power this circuit using a battery, but in order to know what capacity battery I need I want to know the total current consumption of the circuit. How do I do this? I have a ammeter. I am wondering where do I measure the current? Do I just place the ammeter in series with the power supply?

 

I am using a ESP32 as a transmitter circuit for a small project. Essentially the circuit is an ESP32 connected to a pushbutton. As the button is pressed, an IR LED emits a signal that is programmed via Arduino IDE on to the ESP32. I want to power this circuit using a battery, but in order to know what capacity battery I need I want to know the total current consumption of the circuit. How do I do this? I have a ammeter. I am wondering where do I measure the current? Do I just place the ammeter in series with the power supply?

You could do that. However, you need to be aware of the unseen consequences. Every ammeter has series resistance which is known as the burden resistance or shunt resistance. This will reduce the supply voltage at your circuit. You need to look up the specifications of the meter. It would be a good idea to make a measurement to confirm this value.

An alternative is for you to introduce your own shunt resistance. Use your voltmeter to measure the voltage across the resistor and then calculate the current. This will also tell you how much voltage you are losing at the load.

If you have a variable voltage bench power supply, you can increase the supply voltage to compensate for the voltage drop across the shunt resistor. This will give you the correct power consumption at the corrected supply voltage.

 

You could do that. However, you need to be aware of the unseen consequences. Every ammeter has series resistance which is known as the burden resistance or shunt resistance. This will reduce the supply voltage at your circuit. You need to look up the specifications of the meter. It would be a good idea to make a measurement to confirm this value.

An alternative is for you to introduce your own shunt resistance. Use your voltmeter to measure the voltage across the resistor and then calculate the current. This will also tell you how much voltage you are losing at the load.

If you have a variable voltage bench power supply, you can increase the supply voltage to compensate for the voltage drop across the shunt resistor. This will give you the correct power consumption at the corrected supply voltage.

So you are saying, place a resistor in parallel with my power supply of my circuit and measure the drop across that parallel resistor to get my current value?

 

So you are saying, place a resistor in parallel with my power supply of my circuit and measure the drop across that parallel resistor to get my current value?

No. Think circuit theory and Ohm’s Law.

Every ammeter has a burden resistance. This resistance goes in series with the power supply. The ammeter displays current by measuring the voltage across the resistor.

By using your own external series resistor you are doing exactly what the ammeter does, except this time you get to choose the value of the resistor.

 

No. Think circuit theory and Ohm’s Law.

Every ammeter has a burden resistance. This resistance goes in series with the power supply. The ammeter displays current by measuring the voltage across the resistor.

By using your own external series resistor you are doing exactly what the ammeter does, except this time you get to choose the value of the resistor.

Yes, I understand now thank you! Any more tips?

 

hi,
The ESP32 consumes approx 150ma to 250mA average.
What voltage battery voltage are you using and, how long do you want the project to operate ?
E

 

hi,
The ESP32 consumes approx 150ma to 250mA average.
What voltage battery voltage are you using and, how long do you want the project to operate ?
E

That leads me to my next point. The particular circuit with the ESP32 is a transmitter circuit which, when the button is pressed, activates an IR LED to send a signal to another circuit in the room which is connected to a servo motor which will turn on or off the light switch. So ideally, I would like the battery to last as long as possible.

 

I would like the battery to last as long as possible.

hi Sean,
It is important that you state a minimum operating time.
E

 

hi Sean,
It is important that you state a minimum operating time.
E

Okay, let's say one (1) year

 

Hi S,
Will your Arduino coding put the ESP32 into Sleep mode between button pushes?
E

 

Hi S,
Will your Arduino coding put the ESP32 into Sleep mode between button pushes?
E

Yes, it will.

 

For maximum battery life, the push button is placed in series with the battery. Power is consumed only when the button is pressed.

The other option is to place the device in sleep mode when not being used.

 

For maximum battery life, the push button is placed in series with the battery. Power is consumed only when the button is pressed.

I have the pushbutton connected to a pulldown resistor which is connected to a GPIO pin on the ESP32. So when the button is pressed the ESP32 outputs a function which causes the IR LED to output a particular signal.

 

Why are you using ESP32 to activate IR LED?
There are simple circuits to send IR data already.

 

Why are you using ESP32 to activate IR LED?
There are simple circuits to send IR data already.

The IR LED is not the only function of this circuit

 

The IR LED is not the only function of this circuit

Ok, fair enough.

 

Hi Sean,
As you are a Student, is this a college or homework assignment?

Moderation.

 

Hi Sean,
As you are a Student, is this a college or homework assignment?

Moderation.

No, this is a personal project I am working on.

 

A hypothetical example: My ESP32 Runs off a 3.3VDC power supply, it does not use deep sleep mode and draws 425mA 100%time in 24hours. Also the IR led circuit draws 12mA and is on 23% of the time every 24 hours. It does not use WIFI or Bluetooth the step down converter specs 82% efficient.
With this estimate, What size battery would I need to keep it running for 1 day.

Could I step down an 18V cordless drill battery rated 3Ah from Harbor freight and measure that before and after 24hrs?
Since this is one of my personal projects and inflation is affecting cost, I just want to do some math before investing in a battery.

What kind of DC to DC step down converter do I look for that works for most uC applications,
About how many Watts? , Will I need more filtering, I have some of these 500kHz and they look noisy,
Pololu 3.3V, 500mA Step-Down Voltage Regulator D24V5F3

 

In your calculations, you would have to take into account battery self-discharge. In a period of 1 year, even the better lithium batteries will lose some charge.