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Topic: measure AC ampere and monitoring/signal (Read 588 times) previous topic - next topic

islington1

dear forum i'm new from here,

             i am trying to  make a little circuit with arduino nano  or arduino 2009 but not safe of what to do, i've yet done some circuit but more easy.

i have done lot of researches on the google and this forum but got a lot of confusion...

explaning a litle bit my problem.

i have an apareatur that work  with 230 volt AC
this object have on board voltmeter and ammeter

i've got some problem with it so now i need to insert a monitor that
when the power absorption start (0,3/05 Ampere)

a bulb get switch on,

then when the absorption reach 1,3/1,5 Amp. a buzzer comunicate it.

and in the same time i've to register the value if possible with date/hour

can someone help me ?

i don't need a display because i'm planning to leave the original ammeter because i can't broke original schematic.


ive seen the SCT-o13-030 toroidal trasformer it it ok?

or acs712 from allegro


many thanks to all can help me
with sketch etc

sincerelly sergio _T











MarkT

The ACS712 is not rated for mains.

Monitoring current can be done safely with a current transformer (CT).  What range of current is anticipated?
What is the load?  Is it reactive?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

gilshultz

MarkT is correct with the CT however it has an isolated AC output which you will have to convert to DC and filter for a current measurement.  The low pass filter is the critical factor in the design, it controls the accuracy and response time. If you got time no problem.  The voltage is easy if connected properly and is also isolated from the mains.  Use a step down transformer with the primary connected to the mains and the secondary is for the arduino, same filtering etc as the CT circuit but different levels.  In my area my wire insulation on the secondary has to be equal to or greater then the primary insulation rating.  This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

islington1

dear frinds i attach what we tryed me and my friend..

i need to put 2 alarms but not been able and have a better layout of the reading
 can someone help?

raschemmel

ACS723


Quote
This low current sensor breakout is capable of sensing very small currents down to around 10mA and large currents up to 5A!

Wawa

The ACS723 is also not recommended for mains power.
Certainly not for 230/240volt mains (most of the world).
See the note on the Sparkfun page.
Leo..

raschemmel

#6
Dec 10, 2019, 12:46 am Last Edit: Dec 10, 2019, 10:56 am by raschemmel
What note ? All it says is it's not  designed for 2.4 kV.

ACS723 DATASHEET

Quote
Basic Isolation Working Voltage = 420 Vpk / 297 Vrms
240V <297V

1.4*240=336V

336Vpk<420 Vpk

I don't see what you are talking about. The MFG says it's cool so why are you saying it's not ?

Wawa

230/240volt must AFAIK have 4kV isolation and 6 or 8mm creep distance.
I would feel a lot safer with a current transformer.
Leo..

raschemmel

The breakdown voltage for air is 3 million volts per meter , or 3000 V/ per mm, so if the mfg says its rated for 297 V I don't see any reason not to believe it . It would take 300V to arc 0.3 mm so I' sure there's more than enough clearance for isolation.

12Stepper

The breakdown voltage for air is 3 million volts per meter , or 3000 V/ per mm, so if the mfg says its rated for 297 V I don't see any reason not to believe it . It would take 300V to arc 0.3 mm so I' sure there's more than enough clearance for isolation.
900


Wawa

And how much would it be with condensation on a dirty PCB.
I don't see any milled slot in that Sparkfun board.
Tinkerers in the US can be less concerned with 120volt AC.
Leo..

krupski

dear forum i'm new from here,

             i am trying to  make a little circuit with arduino nano  or arduino 2009 but not safe of what to do, i've yet done some circuit but more easy.

i have done lot of researches on the google and this forum but got a lot of confusion...

explaning a litle bit my problem.

i have an apareatur that work  with 230 volt AC
this object have on board voltmeter and ammeter

i've got some problem with it so now i need to insert a monitor that
when the power absorption start (0,3/05 Ampere)

a bulb get switch on,

then when the absorption reach 1,3/1,5 Amp. a buzzer comunicate it.

and in the same time i've to register the value if possible with date/hour

can someone help me ?

i don't need a display because i'm planning to leave the original ammeter because i can't broke original schematic.


ive seen the SCT-o13-030 toroidal trasformer it it ok?

or acs712 from allegro


many thanks to all can help me
with sketch etc

sincerelly sergio _T











You need a current transformer.
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

krupski

ACS723


Are you serious??? First of all, that device measures DC current, not AC. Secondly and much more importantly, there is nowhere near enough isolation to safely separate 230V mains from a 5 volt DC circuit.  At best, this idea will just produce a lot of smoke, at worst..... well need I say it?
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

krupski

#13
Dec 10, 2019, 10:55 am Last Edit: Dec 10, 2019, 10:55 am by krupski
And how much would it be with condensation on a dirty PCB.
I don't see any milled slot in that Sparkfun board.
Tinkerers in the US can be less concerned with 120volt AC.
Leo..
Agreed. I am in the US (120v mains) and NO WAY would I use that little board connected to the AC line. It would be a disaster waiting to happen (even if it DID measure AC current.. which it does not).
Gentlemen may prefer Blondes, but Real Men prefer Redheads!

raschemmel

#14
Dec 10, 2019, 12:10 pm Last Edit: Dec 10, 2019, 12:55 pm by raschemmel
It says 'Galvanically Isolated" .  It also says for 'low current ' applications. I wouldn't run if it got wet and I would probably  clean it with IPA first and put it in a metal box, but given that, yeah I don't see a problem with it. I wholeheartedly agree  that no weekend hobbyist should mess with mains voltage all , for any reason but we've always had posters who couldn't be convinced that there is a "thin red
line" they shouldn't cross but if we accept that this guy is one of those and he's smart enough
to clean it with IPA and seal it in a metal box with silicone sealer to keep out moisture, I don't see 220V as a problem with the distance bewteen those two large round holes on the board for the AC connection. I worked with 277Vrms on a daily basis for 4 years. The product was designed for 240rms but we tested everything at 277V on general principals. I'm not worried about the pcb or the IC. Personally I would never even consider using such a product. A CT or clamp on current probe is the way to go. I'm a big fan of CT's because I've used them before (theyre not expensive either. I have one on my desk at work that is perfect for this application.) I used the (Tek A621) current probe every day for 4 years. The only reason I didn't suggest that is because then the OP is in the loop for all the wiring and circuitry from the CT on. With the Sparkfun board , it's plug & play to the arduino. I would be more worried about the OP not realizing current is measured in series. If I had access to 220V I would test one of them but I would never use one because there's no surge protection. (technically I could
test it with the 220V outlet at work but I don't test personal projects at work on general principles
(the company insurance doesn't allow for that. It's a terminable offense. With they hire someone with
my experience they expect me to know better than to break the rules)
There's no guarantee that the mains will never exceed 220V. With a CT you don't even have to think about that. I'll post the part number for the CT I have at work tomorrow. It  one of these (but I don't remember the part #).
I agree CT is the first choice but then all the rest of the wiring and circuit has to be perfect. With the ACS723, if you're willing to risk a the possibilty of a surge, all the heavy lifting is already done and you just connect it to the arduino like any orher breakout board. If all we're talking about is whether or not the sparkfun board would work if I used it in a sealed metal or plastic box then I say it would work until a surge exceeded the rated 297V. That gap is more than enough for 220V. I know that for a fact from 4 years of ecperience working with 277V and the ACS723 is galvanically isolated. Do I think a hobbyist should use one ? That's their call but I stand on the board will work. (for 220V) If the OP can be trusted to do any wiring then I vote for the CT approach, but the 'weak link' here is the OP , not the ACS723 (except for the surge case).

RTFM !!!!!!
It DOES measure AC.
You want me to post where it says that ?

"The SparkFun Current Sensor Breakout is a high accuracy board that utilizes the ACS723 for moderate AC and DC "


Quote
900
CORRECT ! (thanks for catching that)

3,000,000 "is to"  1 meter
as
x "is to " 0.3mm

cross multiply

x = 900V.

Quote
And how much would it be with condensation on a dirty PCB.
I don't see any milled slot in that Sparkfun board.
That's not the manufacture's fault. Clean the board with IPA and seal it in a box and then that
comment goes away. Let's not even get into the "Should tinkerer's mess with mains AC ?" debate
because there's only one answer to that and not all posters agree about it.
With freedom, comes risks. Is telling someone not to do something enough ?
If they never post again you have your answer.

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