power consumption System for electrical devices

Thread Starter

Fanfire174

Joined Mar 13, 2018
236
Hi guys

I am looking advice to design smart power consumption monitoring system. I want to design a system that will measure the power consumption of device such as light bulb, Fan, cooler etc and It will store the record of power consumption into database server so we can monitor the electricity usage of each devices

I have searched on internet and I found that raspberry pi or ESP8266 can be use in this project. I don’t have idea how raspberry pi or ESP8266 measure power consumption. I mean which circut or sensor require to design system. I think have to use ADC chip but don't know others

I am looking advice to design system. Do I need sensors to measure power consumption of devices ? What do I need to measure power consumption of each devices?
 
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Thread Starter

Fanfire174

Joined Mar 13, 2018
236
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Thread Starter

Fanfire174

Joined Mar 13, 2018
236
The CT for current and needed would be the voltage measuring instrument-means.
Max.
I have to measure voltage and current for power consumption

Current clamp sensor used to measure the current

I think I have to use Current clamp sensor, ADC and Raspberry. Do I need to use anything else like voltage sensor to measure voltage?
 
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-live wire-

Joined Dec 22, 2017
907
Do you want to measure real or apparent power? You generally pay only for real power. An unloaded transformer may consume apparent power but almost no real power. And measuring real power can be a lot more complex.
 

Alec_t

Joined Sep 17, 2013
10,909
There's probably an app for a phone to monitor its own power consumption and log the data. As for monitoring the other appliances, there are already many commercial devices for energy monitoring and logging. Probably cheaper to buy than to build your own.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
236
There's probably an app for a phone to monitor its own power consumption and log the data. As for monitoring the other appliances, there are already many commercial devices for energy monitoring and logging. Probably cheaper to buy than to build your own.
Now as electronics hobbyist I just only want to know if we want to design this type of system then what hardware and component required

The list I made is quite enough or I need something else
 
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-live wire-

Joined Dec 22, 2017
907
Now as electronics hobbyist I just only want to know if we want to design this type of system then what hardware and component required

The list I made is quite enough or I need something else
Apple is VERY secretive. You need a special chip just to get a 5V output, and it doesn't just need a 5V power supply to charge (it also needs certain resistors or certain data wires shorted). So I highly doubt they would let you modify it like that. And you couldn't add some circuit inside your phone, as there is essentially no free space.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
236
AppleYou need a special chip just to get a 5V output, and it doesn't just need a 5V power supply to charge (it also needs certain resistors or certain data wires shorted)..
Thanks for pointing important point. now i will be only focused on AC device. I need tow sensor's voltage sensor to measure voltage drop across AC device and Current sensor to measure current flowing throw AC device

Power = Voltage * Current
 

-live wire-

Joined Dec 22, 2017
907
Thanks for pointing important point. now i will be only focused on AC device. I need tow sensor's voltage sensor to measure voltage drop across AC device and Current sensor to measure current flowing throw AC device

Power = Voltage * Current
But there is a difference between real, apparent, and reactive power. You probably pay for real power, not reactive power, though a volt and ampmeter would measure apparent power. AAC has a good article explaining it. But you will need to learn about capacitors and inductors for it to make sense.
https://www.allaboutcircuits.com/textbook/alternating-current/chpt-11/true-reactive-and-apparent-power/
 

AnalogKid

Joined Aug 1, 2013
8,308
You need to define the requirements a bit better. The range of things listed in post #1 go from 3.6 Vdc to 240 Vac. No simple voltage or current sensor can cover that range. If you have devices groupls according to their input power requirements, that can be used to define a set of sensors for each group.

ak
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
236
You need to define the requirements a bit better. The range of things listed in post #1 go from 3.6 Vdc to 240 Vac. No simple voltage or current sensor can cover that range. If you have devices groupls according to their input power requirements, that can be used to define a set of sensors for each group.

ak
Okay. assume one AC light bulb connected to AC main supply 230 vAC and I want to know how much power it consume for 1 hours using any microcontroller including ADC

I think I need only two sensors. current sensor to measure current throw bulb and voltage sensor to measure voltage drop across bulb

I am confused with voltage sensor if voltage drop is 9v AC (assume any device that consume 9v AC ) then how the microcontroller will know this voltage because it works only 5v DC
 

LesJones

Joined Jan 8, 2017
2,503
I don't see where the 9 volts SC comes from in post #15. The voltage across the bulb would be the mains voltage. (About 230 volts.) But you must measure it's actual value to calculate the power. You would not feed 230 volts AC directly to the ADC. The voltage would have to be scaled down and converted to DC so that it was within the ADC input range. You would probably use a transformer for isolation so this could scale down the voltage. If you did this you would need to use an active rectifier as a diode bridge would give about 1.4 volts voltage drop. If you did not need high accuracy you could use a transformer with a relativly high voltage secondary and a bridge rectifier (This would give a smaller percentage error than using a bridge rectifier with a low voltage.) and then scale the voltage down with a potential divider.

EDIT. I've just noticed AK's comment in post #14 that you need this device to work with both DC and AC from 3.6 volts to 240 volts. If this is so then ignore my comments above. Also if this is the case it makes the design much more difficult.

Les.
 
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Thread Starter

Fanfire174

Joined Mar 13, 2018
236
I have made block diagram to understand interfacing of all units I want to be a correct block diagram before doing any calculation for power.

I have doubt on the input / output connection of light bulb and voltage sensor

  1. Raspberry Pi
  2. ADC
  3. Voltage sensor
  4. current sensor
  5. LCD
  6. Light Bulb
upload_2018-9-1_16-6-1.png

Required sensor
I don't understand where input/output of bulb and voltage sensor goes . positive and negative main supply will goes to two terminal of light bulb. I think the output of voltage sensor would be goes to ADC
 

LesJones

Joined Jan 8, 2017
2,503
You need to clarify the specification of the device you are trying to build. The two links in post #18 are for a current transformer to sense current and a transformer to scale down the voltage from 120 volts to 9 volts. Both of these devices will ONLY WORK WITH AC. You then go on to talk about positive and negative of the main power supply (I assume you mean the supply powering the load.) Positive and negative only make sense with DC. (Or instantaneous values with AC.)

Les.
 

AnalogKid

Joined Aug 1, 2013
8,308
Okay. assume one AC light bulb connected to AC main supply 230 vAC and I want to know how much power it consume for 1 hours using any microcontroller including ADC. I think I need only two sensors. current sensor to measure current throw bulb and voltage sensor to measure voltage drop across bulb. I am confused with voltage sensor if voltage drop is 9v AC (assume any device that consume 9v AC ) then how the microcontroller will know this voltage because it works only 5v DC
Connect a small power transformer to the AC line in parallel with the light bulb. Something with a secondary voltage of 12 Vac or so.
Use a diode bridge and filter capacitor to convert that to a DC voltage.
Use two resistors to divide the DC voltage down to something less than 5 V.
Use the uC A/D to convert the DC voltage value to a digital value.
Measure the AC voltage directly with a meter.
That meter reading now equates to that digital value. This sets the scale for other readings.

There is an error introduced by the two diodes in the bridge, but that can be tweaked out with more software.

ak
 
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