hey all, so a few months ago I talked about designing some kind of a smart grid project for my final year applied project. My team and I have put together a rough schematic that I would like to share with you.


the purpose of our project is to create a specially designed circuit that is powered from the mains line, and can be inserted into every receptacle in a persons home. This circuit powers a pic microcontroller (we are unsure of the exact model as of yet), which receives inputs from various sensors (lux sensors for example) and relays data from its input to a wifi module that sends the data to a hardware peripheral (perhaps a more beastly pic or a raspberry pi) which collects the data, and then relays it to a user through a GUI interface (which we will code and design)

the goal is to demonstrate to users the amount of power their loads are consuming (from each receptacle), and incorporate the use of sensors to automate their lighting settings (e.g. if it's bright outside, the lights in a persons home will be dim, or may even be turned off).

So with that in mind, here's my main question

1: If we power the device from the mains line by splitting the mains feed to a bridge rectifier, which is then stepped down by a voltage regulator to the pic, then how do we determine how much current is running through that circuit? Please take a look at the image below for more info.

 

transformerless power supplies from mains are agains the rules of this forum for safety reasons..
get a transformer on there.. and resize the pic so its not gigantic.

 

You're re-inventing the wheel. Google 'power monitor'. Lots of hits, including
http://www.google.co.uk/url?sa=t&rc...CgIUKRyTudGu_JQ&bvm=bv.53537100,d.ZGU&cad=rja

 

You're re-inventing the wheel. Google 'power monitor'. Lots of hits, including
http://www.google.co.uk/url?sa=t&rc...CgIUKRyTudGu_JQ&bvm=bv.53537100,d.ZGU&cad=rja

Alec what we're trying to do is incorporate the wifi module into the sensing module so that we can relay the information to a users' computer where they can view the load characteristics of each receptacle.

 

OK. Good luck with the project.

 

If you power your PIC with an isolated power supply (which should be easy), this project might conform to forum rules. If not this thread will be closed.

Also, what powers the light bulb circuit? The need to establish a base-emitter voltage on that transistor requires a connection of the power supplies. If the bulb is DC powered, you could instead use an opto-isolator to accomplish the same thing WITH isolation between the power supplies.

If the light bulb circuit is running on 120VAC, you may still be running afoul of the forum rules. And you'll need something other than an NPN transistor or an opto-isolator to achieve the control you want.

 

If you power your PIC with an isolated power supply (which should be easy), this project might conform to forum rules. If not this thread will be closed.

Also, what powers the light bulb circuit? The need to establish a base-emitter voltage on that transistor requires a connection of the power supplies. If the bulb is DC powered, you could instead use an opto-isolator to accomplish the same thing WITH isolation between the power supplies.

If the light bulb circuit is running on 120VAC, you may still be running afoul of the forum rules. And you'll need something other than an NPN transistor or an opto-isolator to achieve the control you want.

Hi Wayneh,

Thank you for expressing your concern, safety is our top priority as well, especially if we want this to be a viable project for the marketplace. Our concern with an isolated power supply ultimately stems from a desire to try to minimize current draw to the circuit, so that users can optimize their energy usage (without our smart circuit consuming too much power).

Out of respect for this forum, I will request that you close this thread until we sort out our power supply issues. Thank you for the warning (and to mcgyvr as well)

As well, I should mention that the transistor should be a TRIAC....my apologies....late night

 

To get up and running, just use a 5V USB power supply, like one you'd use to charge a camera or smartphone. Of course it needs to be rated to higher current than you need. You could also use an old computer PSU to supply gobs of 5V current.

I don't know how the mods will feel about the AC powered part of the circuit, under control of your triac, but my suggestion is to proceed and, worst case, they'll come in and tell us the thread can't continue. Many, many topics here are about AC-powered devices or projects, so I don't want to presume what the mods will decide. The usual formula for closing a thread is: obvious noobie + dangerous idea = closed thread. It's all about the safety of the visitors here.

 

Well I will say that there is no way we will begin building without consent from our professors and our project manager. That is guaranteed, and we still have to have our design approved before we do any type of building

That being said, the triac is used to control the brightness of the light bulb, and allow us to dim it using PWM to adjust the duty cycle.

For anyone interested, here is our inspiration for this project

http://www.safeplug.com/ (check out the video at the bottom)