Generate AC current for tesing

I am making an arduino based system that detects when current in a line falls below a particular threshold. I am using a 5A Hall effect sensor which operates in the range of -5A to +5A current.

For testing the module I would need to generate 2 current levels one above the threshold of 3A and one below. Say two current levels at 2A and 4A. Getting DC currents of such values is fairly simple but I want to generate AC current at 50Hz. The power supply in my country is around 230V, 50Hz.

What is a good and safe way to generate these currents?

I'm not sure where you are located (UK ??)

Probably your easiest option is for the high current is to buy a 12V lighting transformer and a 50W lamp e.g. from Maplins if you are in the UK but any DIY store should probably sell them

http://www.maplin.co.uk/p/105w-low-voltage-lighting-transformer-nl48c

To reduce the current, you could try putting 2 or more 50W lamps in series.

rogerClark:
I'm not sure where you are located (UK ??)

Probably your easiest option is for the high current is to buy a 12V lighting transformer and a 50W lamp e.g. from Maplins if you are in the UK but any DIY store should probably sell them

http://www.maplin.co.uk/p/105w-low-voltage-lighting-transformer-nl48c

To reduce the current, you could try putting 2 or more 50W lamps in series.

I am right now based in India. I understand this method. Its safe and I believe it will work. But it is a very indirect method I feel. And also rather expensive. I am looking for a more direct and price effective way. Since this part is required primarily for testing, I am not inclined to spend too much on this.

Ah OK (I'm not in the UK either, I'm in Australia but we use 240 to 250V not 230).

I thought you wanted a low voltage solution :wink: which would be safe.

A cheap solution is to use any resistive electrical load you have that runs on 240V

Find any electrical appliance that takes 1Kw and it will give you around 4A. e.g. do you have an electric kettle, or perhaps an electric fire.

Putting 2 electric kettles in series will give you less current.

I have an electric oil filled radiator I use for this sort of testing, as its got 3 different power settings.

Note. This is not a safe option, as you are now dealing with mains power, but it will be the cheapest option I think, as you can probably get the appliances for nothing if you borrow them etc

Hi, we in Australia have been 230Vac since 2000.
http://www.powercor.com.au/docs/pdf/Customer%20Information/ESAA%20-%20Residential%20Customer%20Guide%20to%20Electricity%20Supply.pdf
Page 27.
But getting 2 to 4 Amps AC, is the problem at safe voltage level.
What device are you going to be monitoring the current in?
Can you use that with a DMM to calibrate the current sensor?

Tom....... :slight_smile:

Can you use that with a DMM to calibrate the current sensor?

Excuse me interrupting. What is a DMM?.

Thanks.

Hi Tom, thanks for the technical information.

I was just basing my response on what I appear to receive from the grid most of the time

Currently getting 244V at 7:30pm. I"ve seen this climb above 250V on sunny days when all the local PV houses start producing.

Ryanmackie:
What is a good and safe way to generate these currents?

What is your level of proficiency in dealing with mains voltage electricity, bearing in mind that the voltages are easily enough to kill you?

Excuse me interrupting. What is a DMM?.

Digital Multi Meter

i.e something that can measure the cutrrent .i.e part of the DMM is a Digital Amp Meter
But DMM's also measure Voltage and usually resistance and often other things like capacitance, and inductance etc

Hi, DMM yes digital multimeter, if you are gong to be working with electricity and electronics you will find one invaluable.
Even a cheap one, just make sure it can measure AC amps, most will measure to 10A which is fine.

Re, 250Vac Roger, same here, and 430Vac phase to phase. I live just down the road from you, the city with the castle and gold village.

Tom.... :slight_smile:

PeterH:

Ryanmackie:
What is a good and safe way to generate these currents?

What is your level of proficiency in dealing with mains voltage electricity, bearing in mind that the voltages are easily enough to kill you?

The safety is one of my primary concerns. Otherwise I can maybe think of placing a few resistors and taking from the direct line supply. I believe i am smart enough not to kill myself but I would prefer to use a reasonably safe way so that I dont have to worry too much.

TomGeorge:
Hi, we in Australia have been 230Vac since 2000.
http://www.powercor.com.au/docs/pdf/Customer%20Information/ESAA%20-%20Residential%20Customer%20Guide%20to%20Electricity%20Supply.pdf
Page 27.
But getting 2 to 4 Amps AC, is the problem at safe voltage level.
What device are you going to be monitoring the current in?
Can you use that with a DMM to calibrate the current sensor?

Tom....... :slight_smile:

Yeah I will initially use a DMM to calibrate it and once i have two different levels I would feed them into a ACS712 based hall effect current sensor.

http://www.icstation.com/product_info.php?products_id=1707#.U6AaxJSSwkg

This is the sensor I plan to use.

rogerClark:
Ah OK (I'm not in the UK either, I'm in Australia but we use 240 to 250V not 230).

I thought you wanted a low voltage solution :wink: which would be safe.

A cheap solution is to use any resistive electrical load you have that runs on 240V

Find any electrical appliance that takes 1Kw and it will give you around 4A. e.g. do you have an electric kettle, or perhaps an electric fire.

Putting 2 electric kettles in series will give you less current.

I have an electric oil filled radiator I use for this sort of testing, as its got 3 different power settings.

Note. This is not a safe option, as you are now dealing with mains power, but it will be the cheapest option I think, as you can probably get the appliances for nothing if you borrow them etc

Yeah this is the way that I thought about doing it but its kind of unsafe. I havent really experimented on line voltages but can you tell me if standard resistors can be put to use?

Digital Multi Meter

i.e something that can measure the cutrrent .i.e part of the DMM is a Digital Amp Meter
But DMM's also measure Voltage and usually resistance and often other things like capacitance, and inductance etc

Hi, DMM yes digital multimeter, if you are gong to be working with electricity and electronics you will find one invaluable.
Even a cheap one, just make sure it can measure AC amps, most will measure to 10A which is fine.

:sweat_smile: I've got one. I've always called it just "multimeter" (in english. By the way, in spanish we call it "tester". :). Paradoxical, isn't it?)

Ryanmackie:
The safety is one of my primary concerns. Otherwise I can maybe think of placing a few resistors and taking from the direct line supply. I believe i am smart enough not to kill myself but I would prefer to use a reasonably safe way so that I dont have to worry too much.

Mine too. Most mains voltage transformers would give you a rectified output, which you don't want here. Working with AC mains voltage loads would be your easiest approach but in order to do this you need to deal with mains voltage wiring. If you have enough understanding and discipline to do this safely then it would IMO be a reasonable approach to take. The way I would so this is connect the sensor to a cable between an ordinary mains plug and a multi-socket extension cable, so that you are monitoring the current drawn by whatever you plug into the extension. While doing this make sure the plug is disconnected from the mains at any time you are working on the wiring, and that before you plug it in there are no exposed live metal parts, connectors or wires. I don't think your sensor will need to be electrically connected to the mains circuit, but if it was then those precautions would extend to it, and anything connected to it. Also make sure that the wiring you use is rated for the voltage and current you will be using. If you're using a standard extension cable rated at 5A or more that should be fine.

You can control the current by plugging devices into the extension outlet. To get 2A you need about 500W of load, which you could make up from ordinary light bulbs or find some device such as a toaster or microwave which uses this much power. To get the 4A, just plug in more loads. Remember you will need to be clear whether your current figures are peak or RMS and scale the loads accordingly.

There are ordinary consumer current meters which you can fit between the wall outlet and the plug for your extension, which would give you a reasonably accurate indication of the amount of current that was actually being drawn, for comparison with your measurements.

PeterH:
Mine too. Most mains voltage transformers would give you a rectified output, which you don't want here. Working with AC mains voltage loads would be your easiest approach but in order to do this you need to deal with mains voltage wiring. If you have enough understanding and discipline to do this safely then it would IMO be a reasonable approach to take. The way I would so this is connect the sensor to a cable between an ordinary mains plug and a multi-socket extension cable, so that you are monitoring the current drawn by whatever you plug into the extension. While doing this make sure the plug is disconnected from the mains at any time you are working on the wiring, and that before you plug it in there are no exposed live metal parts, connectors or wires. I don't think your sensor will need to be electrically connected to the mains circuit, but if it was then those precautions would extend to it, and anything connected to it. Also make sure that the wiring you use is rated for the voltage and current you will be using. If you're using a standard extension cable rated at 5A or more that should be fine.

You can control the current by plugging devices into the extension outlet. To get 2A you need about 500W of load, which you could make up from ordinary light bulbs or find some device such as a toaster or microwave which uses this much power. To get the 4A, just plug in more loads. Remember you will need to be clear whether your current figures are peak or RMS and scale the loads accordingly.

There are ordinary consumer current meters which you can fit between the wall outlet and the plug for your extension, which would give you a reasonably accurate indication of the amount of current that was actually being drawn, for comparison with your measurements.

I have a Digital Multimeter. I will use that. I think this is the best way to try this. Thank you very much. But how are you calculating the amount of load that will take in a certain amount of current? It it from experience/experiment or did you just calculate it?