AC Current Measurement

Hello Qasim,

I would highly recommend using the MSP430i2041 (4 ADC channels), MSP430F6736A (3 ADC channels), MSP430F6779A (7 ADC channels) for this application. Please check out the Energy Measurement Design Center (EMDC) GUI and software library for these devices. They feature integrated 24-bit Sigma Delta ADCs with differential inputs and integrated programmable gain amplifiers. You could easily leverage EMDC with another wireless MCU (like the CC2652) to send the measurements wirelessly. EMDC supports several AC current sensors including shunts, current transformers, and rogowski coils.

You can read more about EMDC in the following blog post.

Accelerate your metering design with the new Energy Measurement Design Center and software library for MSP430™ MCUs

Regards,

James

Qasim Ahtesham said:

I am assuming these MCUs can then switch 23 relays as well, right?

Sure, a host MCU could be used to control the relays.

Qasim Ahtesham said:

According to the current measured from each outlet, I want to control a relay. Any suggestions?

Assuming you need 23 current sensors, then you'll need multiple devices to accomplish this. Let's assume you used 23 MSP430i2021 devices. They could send the measured current to the host MCU who could switch the relays on or off accordingly. There are probably other configurations that could do the same thing.

Regards,

James

Hi James, 

I have one more question please. I was looking at this controller (MSP430F6459-HIREL) which has 12 ADC channels.

What does this mean? It can measure 12 analog values in parallel (has 12 ADCs)? Or, it has only one ADC, but 12 channels multiplexed? So it will only measure one analog value at one time? If so, then what will be the time difference between measuring each value?

Thank you.

Qasim Ahtesham said:

I have one more question please. I was looking at this controller (MSP430F6459-HIREL) which has 12 ADC channels.

What does this mean? It can measure 12 analog values in parallel (has 12 ADCs)? Or, it has only one ADC, but 12 channels multiplexed? So it will only measure one analog value at one time? If so, then what will be the time difference between measuring each value?

Yes, the ADC inputs are multiplexed and sampled sequentially at the sampling frequency. You can find more valuable information about the ADC12 module in Chapter 28 in the MSP430x5xx and MSP430x6xx Family User's Guide.

Regards,

James

Qasim Ahtesham said:

Lastly, what is the difference between a normal MCU and a host MCU?

If you need to measure 23 sensors, you'll exceed 12 channels (assuming you're using MSP430F6459-HIREL) or 7 channels (assuming you're using the MSP430F6779A). Thus, you'll need more than one devices. Now, let's assume you used 6 MSP430i2041 devices (6 x 4 channels). You'd want to use another "host MCU" to configure, co-ordinate, and capture the data sent by the devices used as analog front ends (AFEs).

What type of current sensors are you planning to use?

Regards,

James

James Evans said:

If you need to measure 23 sensors, you'll exceed 12 channels (assuming you're using MSP430F6459-HIREL) or 7 channels (assuming you're using the MSP430F6779A). Thus, you'll need more than one devices. Now, let's assume you used 6 MSP430i2041 devices (6 x 4 channels). You'd want to use another "host MCU" to configure, co-ordinate, and capture the data sent by the devices used as analog front ends (AFEs).

What type of current sensors are you planning to use?

I am happy to use any current sensors which can be reliable used with any of the MCUs of TI. 

So, from what I have understood, any of the Host CPUs can gather the data from 23 sensors (coming actually from maybe 6 or even 23 MCU unit),)  process it, and switch 23 relays?

Thanks for your help James.

Thanks James. Does TI manufacture any CTs? or any current sensors which you manufacture/recommend?

Qasim Ahtesham said:

Thanks James. Does TI manufacture any CTs? or any current sensors which you manufacture/recommend?

TI doesn't manufacture CTs, and unfortunately, I don't have any specific recommendations. I'd recommend searching online.

Regards,

James

Qasim Ahtesham said:

Also, can you please enlighten me with which of the MCUs are capable of communicating via Modbus? I need to read data from Victron devices into the MCU.

I'd recommend searching for this online and in our forum as well. Here are two threads that I found.

impliment the MODBUS protocal in msp430f249

implementing MODBUS communication on MSP430F5438

Regards,

James