EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: jonwhite on November 22, 2016, 04:22:52 pm
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Hello
Wonder if someone would be interested in designing a circuit for me please noting too complex just using a current sensor
Please pm me if you are interested
Thanks
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Could you explain what the circuit should do?
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Hello
ts using a current sensor and using it as a switch when ac current gets to 100ma the circuit off basically acts as a switch
Using an acs 712 sensor 20 amp version measjring ac 240v 50hz signem
Please do get in tojch if you could nelp me please my email jonisinht35r@gmail.com
Kind regards jon
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You know you can buy the break out boards for those sensors?
Are you after someone turning a "Arduino" type prototype / proof of concept into a single board design (rather than having multiple shields hanging off a board)?
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No
Im designing the board just need some help with the design of the circuit really.
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The ACS712 isn't good at measuring very low currents, specially the 20A version, that has a low resolution, making 100mA hard to read on an Arduino (whose ADC is only 10-bit, and if that is what you're going with).
Another thing that makes the ACS712-20 hard to use for small currents is that it is extremely noisy.
If you're adamant on using the ACS712, I suggest you use an ADC with a resolution ? 16-bit.
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What is the application?
What causes the input current?
What will you be switching on the output?
Will it have to interact with other systems or just switch based on the current?
Would it be easier to just buy an off the shelf current relay instead of making something yourself?
You mention 100 mA as the switching threshold.
Is that 100 mA true RMS or can we assume it to be a sine (peak 141 mA)?
What precision do you need? Should it switch within 1% of the set value? Or is 100 mA just a margin to distinguish a device running (drawing much more than 100 mA) from spurious currents?
How do you intend to power the device?
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The ACS712 is a convenient choice for measuring modest DC current when you need isolation.
But if you are using low frequency AC, go with a tradition AC current transformer. It will provide robust isolation with a quiet signal.
I've also made my own current sensors with linear hall effect sensors and toroid cores.
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A 712 in that application is something I wouldn't touch. That combination with a 328 is quite drifty. At a half amp DC I only got 22 counts and at least 5 of that was noise The AC could be amplified and rectified and you might have a chance. A current sense coil would be better with multiple turns.