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Entering the EV world — Parallax Forums

Entering the EV world

iseriesiseries Posts: 1,516
in Customer Projects

First think I notice was driving past a gas station looking at the gas prices only to realize it doesn't matter.

I am used to pulling up to the gas pump and seeing how much gas and what it cost me. Now I plug it into an outlet at my house and have no idea what I just did. There is no pump fuel gauge or cost to tell me what just happened.

There are devices that can be installed in the power panel that will monitor everything that goes on in your house. Emporia is one of these devices.

I was thing of DIYing it with building a ferrite core and cutting it in half and monitoring with a hall effect sensor. This seems a little much and now looking at a different solution.


This takes some of the DIY out of the project and make a simple device that outputs 40ma per amp of power.

Now I need to build a program that converts the voltage into amps and displays it or maybe sends the data to my network for processing. I would need to monitor how many amps per hour are used to come up with a cost to charge an EV as we pay for power by the kilowatt hour.

I was thinking that a P2 could easily do this by using the analog feature of the pin with a resistor function added across as the circuit needs an added resistance to measure the voltage.

The only thing is how to measure time.

Comments

  • ManAtWorkManAtWork Posts: 2,267

    This is a simple current transformer? Ok, this is better than the linear hall effect sensor as it doesn't have offset and temperature drift problems. But you should also measure the voltage, say every milli second, and then multiply current times voltage to get power (kW) and then integrate that over time to get energy (kWh). This way you measure true RMS current. Only measuring (average) current will produce errors when there is reactive current, e.g. the power factor is not 1.0.

  • iseriesiseries Posts: 1,516

    The unit I am looking at is CTS-CS-CAX-10-050. This unit require 5 volts to power it and returns a voltage based on current flow. Not sure how this works.


    If the P2 is running at 200Mhz and I setup a loop to read every millisecond how much drift would there be in an hour?

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