220 v AC current indicator

[polle]

Hi

I need help to design a current overload warning indicator.
How to make a device that shows the power consumption of connected appliances by the means of led's liting up as the current is rising.
If I have 10 led's on the device, corresponding to 10 Amps ( 1 led for each amp )
When the maximum current is reached, the 10 led starts flashing.
Thanks for any help

Polle

 

[#12]

As a precision analog guy, I'd start with a low resistance shunt on the 220 line, precision rectifier, LM3914 linear display chip.

I feel sure that a microprocessor guy will be here in just a little while and describe how to make all this obsolete.

Your turn.

 

[crutschow]

To #12's suggestion, I would avoid the danger of directly connecting the circuit to the 220V line by using a current transformer or a Hall effect device for isolation to detect the 220V current.

 

[#12]

Good point, crutschow.

 

[Reloadron]

You have options. There are several ways to go about it. Also depends if this is a kitchen table hobby project or being built for a real world industrial application.

Starting at the beginning you need to sense or sample the AC current in the line. For AC I would start with either a current transformer or hall effect AC sensor. Regardless of the choice of sensor you want a sensor that will give you a signal proportional to the line AC current.

I like using devices like this one to sense AC current. There are dozens of variations of it available globally from different manufacturers. You can also build your own circuit to measure and condition the AC current using a sensor and signal conditioning.

The output can be directly passed along to a comparator network. A good choice is a chip the #12 mentioned, the LM3914 Dot/Bar display driver. The data sheet for which can be found here. Beyond that chip you could build your own string of window comparators using chips like the LM339 or similar comparator. An explanation of comparators can be found here.

How you choose to go about it is pretty much your call and depends on the application.

<EDIT>

To revisit what crutschow mentions and line isolation:

I would avoid the danger of directly connecting the circuit to the 220V line by using a current transformer or a Hall effect device for isolation to detect the 220V current.

Using a current transformer does afford AC line isolation, however, does involve opening (breaking) the AC line to run the current carrying conductor through the current transformer. Obviously this is done with mains power disconnected. Thus as always, a good understanding of AC mains power is essential for safety.

</EDIT>




Ron

 

[4pyros]

sounds like home work to me

 

[polle]

Thanks for the inputs and ideas so far, - still trying to figure it out , so more ideas are most welcome!
As I am an electrician, I am well aware of the hazard working with 220 v AC, but I'm a newbie in design of electronic circuits, though I know the basics.
I've been looking around for design software that meet my needs. Not a easy task with so many to choose from. I have installed 2 programs so far: Circuit wizard demonstration version and the free-ware version of Eagle. I think the Circuit wizard looks very nice and easy to use for simple circuits, but still haven't used it for real. Maybe the library is to small ? And I didn't find any comment for this program inhere?
Eagle seems to be a lot more hard to learn to use, but a lot bigger library for the components.

 

[4pyros]

So is this just for you, and making it once or will you be making alot of these? This INFO will help determine the best option for you. Andy

 

[polle]

So is this just for you, and making it once or will you be making alot of these? This INFO will help determine the best option for you. Andy

This is only for my "toolbox", so I quess one is enough, maybe later one for three phase, that makes four in all.

 

[#12]

This brings up the idea of modifying an amp-clamp meter. Much easier to get around a wire a day than a current transformer, but an actual design requiring job to do. If only there was a DVM that flashed lights and rang bells at 10 amps...