wanted someone to design a small circuit $$$ - Page 1
Forum section: electronics / projects

author: jonwhite
author_rank: Contributor
timestamp: November 22, 2016, 04:22:52 pm
content: HelloWonder if someone would be interested in designing a circuit for me please noting too complex just using a current sensorPlease pm me if you are interestedThanks

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 23, 2016, 12:50:27 am
content: Could you explain what the circuit should do?

author: jonwhite
author_rank: Contributor
timestamp: November 23, 2016, 10:37:52 am
content: Hellots using a current sensor and using it as a switch when ac current gets to 100ma the circuit off basically acts as a switchUsing an acs 712 sensor 20 amp version measjring ac 240v 50hz signemPlease do get in tojch if you could nelp me please my email jonisinht35r@gmail.comKind regards jon

author: Wilksey
author_rank: Super Contributor
timestamp: November 23, 2016, 11:03:34 am
content: 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)?

author: jonwhite
author_rank: Contributor
timestamp: November 23, 2016, 12:27:25 pm
content: NoIm designing the board just need some help with the design of the circuit really.

author: AlxDroidDev
author_rank: Frequent Contributor
timestamp: November 23, 2016, 01:05:03 pm
content: 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.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 23, 2016, 04:50:52 pm
content: 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?

author: DBecker
author_rank: Frequent Contributor
timestamp: November 23, 2016, 05:41:12 pm
content: 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.

author: Seekonk
author_rank: Super Contributor
timestamp: November 23, 2016, 09:39:38 pm
content: 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.