FelipeMB
Newbie
Hi,
Me and my team are developing a LED light controller for street lightning applications.
We are trying to measure current draw, voltage and power consumption using Allegro's ACS71020 but the readings don't seem to make any sense. We have achieved a successful communication using I2C, since we can write and read multiples registers. For example, we changed the default slave address to 0x45, and to do that we had to write the customer code to a specific register, and then set 0x45 address (which involves another write operation). After that, we read the register that holds the I2C slave address and it appears changed. So we take from that that we're reading and writing successfully.
We're testing this IC using the evaluation board ASEK71020KMAB-090B3-I2C. We're using two different step-down circuits (recommended by the chip documentation), which are shown in the schematics attached (let's call circuit 1 to the purely resistive one, and circuit 2 to the one with capacitors).
We're working with a 220V/50Hz power source. For the circuit 1 we're using an Rsense of 2.2k and for the circuit 2 a 1.8k resistance. From these values we have calculated a Full Scale Voltage of 500V for the first circuit and 610V for the latter, using the formulae on the documentation. We used 90A as the Full Scale Current.
After reading the corresponding register (0x20) for the Vrms and Irms readings we use the following code to decode the reading.
v=(RXData[1]*256+RXData[0])/0x8000 ;
i=(RXData[3]*256+RXData[2])/0x4000 ;
Where RXData is an array that stores the received bytes from the I2C reading operation in the order specified by the acs71020 user guide.
To test de ACS71020, we're using an incandescent lightbulb as the target load. Measuring its current draw, we see that it consumes 360mA @220V. The results using either the capacitive circuit or the resistive circuit are pretty similar. When the bulb is off we get Vrms=224V, and i=3.1A ; and when it's on Vrms=224 and i =2.8A.
While the current values are excessively big, what worries us the most is the fact that the current measured is bigger while the light bulb is off than on.
We believe something is wrong with the setup in the chip. We couldn't find any examples of the chip configuration settings.
Here's the C code we're currently using to get the readings:
The raw values from reading the register 0x20:
Kind regards
Felipe
Me and my team are developing a LED light controller for street lightning applications.
We are trying to measure current draw, voltage and power consumption using Allegro's ACS71020 but the readings don't seem to make any sense. We have achieved a successful communication using I2C, since we can write and read multiples registers. For example, we changed the default slave address to 0x45, and to do that we had to write the customer code to a specific register, and then set 0x45 address (which involves another write operation). After that, we read the register that holds the I2C slave address and it appears changed. So we take from that that we're reading and writing successfully.
We're testing this IC using the evaluation board ASEK71020KMAB-090B3-I2C. We're using two different step-down circuits (recommended by the chip documentation), which are shown in the schematics attached (let's call circuit 1 to the purely resistive one, and circuit 2 to the one with capacitors).
We're working with a 220V/50Hz power source. For the circuit 1 we're using an Rsense of 2.2k and for the circuit 2 a 1.8k resistance. From these values we have calculated a Full Scale Voltage of 500V for the first circuit and 610V for the latter, using the formulae on the documentation. We used 90A as the Full Scale Current.
After reading the corresponding register (0x20) for the Vrms and Irms readings we use the following code to decode the reading.
v=(RXData[1]*256+RXData[0])/0x8000 ;
i=(RXData[3]*256+RXData[2])/0x4000 ;
Where RXData is an array that stores the received bytes from the I2C reading operation in the order specified by the acs71020 user guide.
To test de ACS71020, we're using an incandescent lightbulb as the target load. Measuring its current draw, we see that it consumes 360mA @220V. The results using either the capacitive circuit or the resistive circuit are pretty similar. When the bulb is off we get Vrms=224V, and i=3.1A ; and when it's on Vrms=224 and i =2.8A.
While the current values are excessively big, what worries us the most is the fact that the current measured is bigger while the light bulb is off than on.
We believe something is wrong with the setup in the chip. We couldn't find any examples of the chip configuration settings.
Here's the C code we're currently using to get the readings:
C:
float acs71020_get_voltage(){
float aux_v=0;
acs71020_read(REG_IRMS_VRMS);
aux_v=((float)(RXData[1]*256+RXData[0]))/0x8000;
aux_v=aux_v*(FULL_SCALE_V);
return aux_v;
}
float acs71020_get_current(){
float aux_i=0;
float aux_2=0;
acs71020_read(REG_IRMS_VRMS);
aux_2=(RXData[3]&0x7f)*256;
aux_i=(aux_2+RXData[2])/0x4000;
aux_i=aux_i*(FULL_SCALE_I);
return aux_i;
}The raw values from reading the register 0x20:
- When the light bulb is on : 2e 3b 66 02
- When the light bulb is off : fe 3c 2d 02
Kind regards
Felipe
