[SOLVED] current measurment for ac through acs712 microcontroller circuit

[zia]

hi i m required acs712 circuit for AC current measurment.

 

[jayanth.devarayanadurga]

Better use ACS712 module from rhydolabz.com. Interface the module to uC adc and take the measurement.

 

[tpetar]

hi i m required acs712 circuit for AC current measurment.

ACS712 is Hall sensor with integrated OpAmp on output you need just to measure voltage with ADC, no need for any special circuits.

See MikroC code example in my blog.

ACS712-05 5A
ACS712-20 20A 0,5V (-20A) 2,5V (0A) 4,5V (+20A)
ACS712-30 30A
.
.
.



Project examples with 7-seg display:
https://coolcircuit.com/project/digital_amp_meter/picmicro_digital_amp_meter.html


Price for ACS712 is around 2,4USD. Its low cost but requires current to flow through Hall sensor :

Also see A1302 sensor. This Hall sensor do not require current to flow through sensor.



Best regards,
Peter

;-)

 

[zia]

thanx all i had to measure AC current which was solved using lm358.

 

[tpetar]

ACS712 measure AC you dont need additional opamp.

In ACS712 datasheet you will find needed informations.

Example for ACS712-20 (20A) :

At +20A on sensor output you will read 4,5V
At 0A on sensor output you will read 2,5V
At -20A on sensor output you will read 0,5V



Best regards,
Peter

:wink:

 

[harischandraprasad]

I bought ACS712 without op-amp version. But I came to a conclusion to use op-amp in a similar was as shown in datasheet. Planning to use LM358 as I already have it and easily available.

tpetar: As it gives 185mv/A output, the resolution may not be sufficient to measure low current changes with ADC with 10bit(in my case, and I am planning to switching to 12 bit). So, I guess amplification is required.

zia: What gain you have used? I am planning to use 10. Is it possible to share your schematic?

 

[tpetar]

I bought ACS712 without op-amp version. But I came to a conclusion to use op-amp in a similar was as shown in datasheet. Planning to use LM358 as I already have it and easily available.

I didnt hear that ACS712 without OpAmp exist. OpAmp is builtined inside ACS712.

tpetar: As it gives 185mv/A output, the resolution may not be sufficient to measure low current changes with ADC with 10bit(in my case, and I am planning to switching to 12 bit). So, I guess amplification is required.

zia: What gain you have used? I am planning to use 10. Is it possible to share your schematic?

ACS712-5 (±5A) have typical sensitivity 185mV/A
ACS712-20 (±20A) have typical sensitivity 100mV/A
ACS712-30 (±30A) have typical sensitivity 66mV/A

Check output voltage ranges from ACS712 datasheet.

10-bit ADC works fine with ACS712.



Best regards,
Peter

 

[harischandraprasad]

A agree that ACS712(+/-5A) has internal Op-Amp. what I mean by without Op-Amp is, breakout board which does not have extra Op-Amp for more gain.

I am new to this ADC world. So, please correct me if I am wrong.

"10-bit ADC works fine with ACS712" - Its depend on what sensitivity we want. If we want to use this to measure with 1W(at 230V) resolution the step value of ADC that we need to measure is at least 0.8043mv. In my case I am using ATmega16. So, per step I can measure 0.0048mv (5v/1024). So, how can I measure 0.8043 step value without an extra amplifier? Am I missing something in ADC measuring technique? May be if I can reduce the measuring range I can use AREF. Can you please clarify me? It would be great if I can use 10-bit ADC without extra amplification.

 

[tpetar]

"10-bit ADC works fine with ACS712" - Its depend on what sensitivity we want. If we want to use this to measure with 1W(at 230V) resolution the step value of ADC that we need to measure is at least 0.8043mv. In my case I am using ATmega16. So, per step I can measure 0.0048mv (5v/1024). So, how can I measure 0.8043 step value without an extra amplifier? Am I missing something in ADC measuring technique? May be if I can reduce the measuring range I can use AREF. Can you please clarify me? It would be great if I can use 10-bit ADC without extra amplification.

For sure higher ADC resolution (more ADC bits such 12-bit, 14-bit, 16-bit, 18-bit, 24-bit) will give better results. Some µC have integrated 12-bit ADC. Not necessarily to use integrated ADC in µC, you can use external ADC IC with better resolution.


As additional check ACS712 datasheet diagrams for voltage output as result of measurement.

For example :
ACS712-20 (±20)
At 0A will give 2,5V
At 20A will give 4,5V
At -20A will give 0,5V

Measurement of 20A DC is done from 2,5V to 4,5V (2V). For sure higher ADC will give better results, but all depends from project needs. (2000mV/4,88mV = 409steps for 10-bit).

Measurement of 20A AC is done from 0,5V to 4,5V (4V). 4000mV/4,88mV = 819 steps for 10-bit.


Best regards,
Peter

 

[paulfjujo]

Hello,

I want to use ACS712 module from miniinthebox
ACS712 module 20A Hall Current Sensor Module
gives 100mV/per Amps
what do you think concerning tickness of cupper PC board if i want to measure a constant DC current at about 18A (near the maxi range)?
and size of the measurment link inside the ACS712 it self ?
Risk of burning ?



i know that we can pass many amps in a short wire.. depends of the heating W=rI²xT
but diffcult to imagine, when we compare with the size of a shunt 0,1V 15A

 

[tpetar]

Hello,

I want to use ACS712 module from miniinthebox
ACS712 module 20A Hall Current Sensor Module
gives 100mV/per Amps
what do you think concerning tickness of cupper PC board if i want to measure a constant DC current at about 18A (near the maxi range)?
and size of the measurment link inside the ACS712 it self ?
Risk of burning ?



i know that we can pass many amps in a short wire.. depends of the heating W=rI²xT
but diffcult to imagine, when we compare with the size of a shunt 0,1V 15A

PCB should be double sided :

https://lygte-info.dk/info/CurrentAdapter UK.html

ACS712 can handle at least x5 more impulse current than declared maximum current.


For higher current my favorite Hall is A1302. This sensor dont require current pass through sensor :





As additional, your second picture is current shunt for 15A (150mV). Resistor as current shunt is not good for higher current, can do the job but its not good, he waste power, generate heat an lower voltage. At 15A you this shunt will decrease voltage by 2,2V. ACS712 have lower impact on voltage and current in measured circuit, A1302 dont have at all.


Best regards,
Peter

 

[paulfjujo]

hello,

@tpetar , thank's for your reply

At 15A you this shunt will decrease voltage by 2,2V.

nota: shunt 15A will decrease voltage by 150mV only .. it's the given value of all the range .

but i don't want to use it because no galvanic insulation
I allready did some test with Hall effect sensor like this
**broken link removed**
with a litle transfo (any VA) , and your device seems very interrested..
did you use a toroid ferrite element and cut the gap by yourself , to insert the hall effect sensor ?
what sensistivity or relation chip you get with your device mV/Amps ?