Looking for current sensor switch

[aitch1969]

as the title says im looking for a current sensor switch well a few...

i want to use a sensor in a 230v circuit to switch on a low voltage circuit 5v dc

i can find arduino type hall sensors nice and cheap but they give a proportional voltage to represent the current in the 230v circuit BUT i just want a N/O circuit when no current that becomes a closed circuit when current sensed / detected this can be preset at 0.5a or lower but the circuit ill be monitoring could be anything up to 15a

i can also find very expensive current sensing switches that have go/ no go switch but they are too large bulky and expensive,

i want a compact inexpensive reliable module that will just sense 0.5-15a in the 230v ac and then switch on my 5v dc circuit

Not much to ask ?

Many Thanks
Aitrch

 

[Arouse1973]

Can you explain a bit more about the project please?
Cheers
Adam

 

[Minder]

Have you checked out the ASC712 modules on ebay, they are under $2.00.
They go in 5a 10a 20a 30a types.
They typically output 100Mv/amp.
M.

 

[aitch1969]

Have you checked out the ASC712 modules on ebay, they are under $2.00.
They go in 5a 10a 20a 30a types.
They typically output 100Mv/amp.
M.

Many thanks
I've seen the as712 unit's I could be wrong but don't they give an output voltage that is proportional to the current? What I am after is a switch so and current over say 0.5a will close a normally open switch

What I'm making is a control box that will turn on a circuit if a series of switches are on some switches will be pressure differential switches some manually operated switches but also 2 or more of the switches need to be current monitoring switches, hense my request for advice on current monitoring switch .

Thanks
Aitch

 

[Bluejets]

I believe Minder is on the right track here.
Just feed the output into a comparitor maybe 393 and use that to turn on a transistor, mosfet relay or whatever.

 

[aitch1969]

I believe Minder is on the right track here.
Just feed the output into a comparitor maybe 393 and use that to turn on a transistor, mosfet relay or whatever.

So if I get one of these
http://m.ebay.co.uk/itm/ACS712ELC-2...%3Aab7ca1fd1590a5e2a5691eefffb1c51f%7Ciid%3A5
What else do I need to provide a switched output?
The voltage I am switching is 5v
The devises I am monitoring are 230v
I will need to be able to switch at anywhere from 0.5a to 6a lower limit and 3a to 16a upper limit. So upper and lower limit adjustability is preferred but lower limit only would be acceptable.

I would like to use as few components as possible and need to avoid the necessity to program as I don't have a computer.

Many thanks for your help

Aitch

 

[Alec_t]

That sensor has an output which is 2.5V (assuming a 5V supply) when the monitored current is zero, and varies from about 0V to 5V as the current varies from -20A to +20A, i.e it gives a ~5V swing for a 40A current range. Since you want a minimum 0.5A threshold, that means you will need to sense an output change of about +- 5V/80 = +- 62mV. The half-wave comparator will need careful biassing to detect this relatively small change in the presence of possible interference.
Signal attenuation/smoothing/filtering will involve a few components (R, C, pot). The comparator would drive a semiconductor switching device (according to 5V load current).

 

[aitch1969]

S

That sensor has an output which is 2.5V (assuming a 5V supply) when the monitored current is zero, and varies from about 0V to 5V as the current varies from -20A to +20A, i.e it gives a ~5V swing for a 40A current range. Since you want a minimum 0.5A threshold, that means you will need to sense an output change of about +- 5V/80 = +- 62mV. The half-wave comparator will need careful biassing to detect this relatively small change in the presence of possible interference.
Signal attenuation/smoothing/filtering will involve a few components (R, C, pot). The comparator would drive a semiconductor switching device (according to 5V load current).

Sounds like an off the shelf current sensing switch will be my best option :-/ really didn't want to be spending £25 each for them

Thank for the help

Aitch