want to design a two wire 4 to 20 milliamp circuit using xtr116 - uc and lcd with less milliamp

Thread Starter

NAGARAJ_JP

Joined Aug 21, 2020
17
Hi i have decided to have xtr116 for two wire 4 to 20 milli amp circuit. i have to read a 0-100 mv using adc and according to the adc input i have to vary the output current 4 - 20 milli amp and also i have to show the input voltage parameters on the lcd. So i decided to use atmega328 to read the 0-100 mv using the inbuilt adc of the micro controller and to display it on 20x4 lcd, the issue is for the two wire 4 to 20 milli amp all the components must be less than 3 milli amp but in my case the atmega328 and 20x4 lcd takes around 17 milli amps which exceeds the limits so kindly help me out reading a 0-100mv and displaying it in two wire 4 to 20 milli amp.

Thankyou
 

Picbuster

Joined Dec 2, 2013
1,022
Hi i have decided to have xtr116 for two wire 4 to 20 milli amp circuit. i have to read a 0-100 mv using adc and according to the adc input i have to vary the output current 4 - 20 milli amp and also i have to show the input voltage parameters on the lcd. So i decided to use atmega328 to read the 0-100 mv using the inbuilt adc of the micro controller and to display it on 20x4 lcd, the issue is for the two wire 4 to 20 milli amp all the components must be less than 3 milli amp but in my case the atmega328 and 20x4 lcd takes around 17 milli amps which exceeds the limits so kindly help me out reading a 0-100mv and displaying it in two wire 4 to 20 milli amp.

Thankyou
16-24V is used to gain 4-20mA
no way to create more energy to feed a system from the xtr116 ( nice thing I use it also)
You need a power supply running 24V 25 mA to feed the xtr116 via the two wires.
Why would you place a remote mpu + display on a two wire system.
A good system is to read sensor data with a MPU and transfer this using RS485/4-20mA but a remote power sup is needed.
An other way is to add the signal to the power line and split power and data at receivers site.

Picbuster
 

Reloadron

Joined Jan 15, 2015
5,646
Hi i have decided to have xtr116 for two wire 4 to 20 milli amp circuit. i have to read a 0-100 mv using adc and according to the adc input i have to vary the output current 4 - 20 milli amp and also i have to show the input voltage parameters on the lcd. So i decided to use atmega328 to read the 0-100 mv using the inbuilt adc of the micro controller and to display it on 20x4 lcd, the issue is for the two wire 4 to 20 milli amp all the components must be less than 3 milli amp but in my case the atmega328 and 20x4 lcd takes around 17 milli amps which exceeds the limits so kindly help me out reading a 0-100mv and displaying it in two wire 4 to 20 milli amp.

Thankyou
This is the data sheet for the XTR115 and XTR116 Current Loop Transmitters.

Now you mention 4 to 20 mA and 0 to 100 mV. The current loop span is 16 mA. The Atmega 328P has an onboard 10 bit DAC which with a 5.0 volt reference gives you a resolution of only about 4.8 mV. Using an internal reference of 1.1 volt you get down to about 1.0 mV.

Where does the 3.0 mA limit come from because your display alone will well exceed 3 mA.

I suggest you read and understand the data sheet and everything Picbuster mentions above.

Ron
 

Thread Starter

NAGARAJ_JP

Joined Aug 21, 2020
17
16-24V is used to gain 4-20mA
no way to create more energy to feed a system from the xtr116 ( nice thing I use it also)
You need a power supply running 24V 25 mA to feed the xtr116 via the two wires.
Why would you place a remote mpu + display on a two wire system.
A good system is to read sensor data with a MPU and transfer this using RS485/4-20mA but a remote power sup is needed.
An other way is to add the signal to the power line and split power and data at receivers site.

Picbuster
Hi thankyou for the information..

"You need a power supply running 24V 25 mA to feed the xtr116 via the two wires."
im now powering the xtr116 with 24v power supply only the thing is when i connect the micro controller and the lcd the default current drawn by the controller and lcd is 16 milli amp which is to be less than 3 milliamp, i have attached my circuit block along with this message.

"Why would you place a remote mpu + display on a two wire system"
I need to design a two wire 4 to 20 milliamp sensor device and also i have to display it, there are 2 wire 4 to 20 milli amp with display yokagowa and some other are manufacturing it.

thankyouo
 

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Thread Starter

NAGARAJ_JP

Joined Aug 21, 2020
17
This is the data sheet for the XTR115 and XTR116 Current Loop Transmitters.

Now you mention 4 to 20 mA and 0 to 100 mV. The current loop span is 16 mA. The Atmega 328P has an onboard 10 bit DAC which with a 5.0 volt reference gives you a resolution of only about 4.8 mV. Using an internal reference of 1.1 volt you get down to about 1.0 mV.

Where does the 3.0 mA limit come from because your display alone will well exceed 3 mA.

I suggest you read and understand the data sheet and everything Picbuster mentions above.

Ron

"Where does the 3.0 mA limit come from because your display alone will well exceed 3 mA."

yes that is my issue my display and controller eats up more current i need to design a controller and display that will consume power in micro amps..
 

Reloadron

Joined Jan 15, 2015
5,646
Would this be a school assignment?

You are not going to get below 3.0 mA current consumption with anything you mentioned. You don't need a 20 character 4 line display to display a simple A/D voltage and you don't need a Atmega 328 P either. The Arduino Uno used a 328P and when it is not doing anything the current is about 45 mA. Start looking at low power micro-controllers or actually low power A/D chip solutions. Then start looking at low power or ultra low power displays. You really need to much better define your project.

Ron
 

Thread Starter

NAGARAJ_JP

Joined Aug 21, 2020
17
Would this be a school assignment?

You are not going to get below 3.0 mA current consumption with anything you mentioned. You don't need a 20 character 4 line display to display a simple A/D voltage and you don't need a Atmega 328 P either. The Arduino Uno used a 328P and when it is not doing anything the current is about 45 mA. Start looking at low power micro-controllers or actually low power A/D chip solutions. Then start looking at low power or ultra low power displays. You really need to much better define your project.

Ron
thankyou yes im looking for low power lcd i just got through nokia 5110 which will consume 200 micro amp as per data sheet it seems, and for micro controller atmega328 if im going to run with 2v and 1 mhz it will consume in micro amps itseems, need to check.

"Would this be a school assignment?"
there are industrial projects based on 4 to 20 milliamp TWO wire manufactures namely yokogawa..
 

RPLaJeunesse

Joined Jul 29, 2018
112
Using a micro seems just wrong, as it introduces all sorts of resolution and error issues in the current loop path. Just use the input to run the XTR116 directly, and add some sort of 100mV LCD DVM to the system for the local readout.
 
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