April this year Allegro have released hall effect current sensors that have a high degree of accuracy and are temperature compensated. Being hall-effect, there’s an inbuilt degree of isolation, and the ratings are present in the datasheet.
It was the kind of standard I was looking for a project some years down the road, but here they are!
They’re 50-200A uni or bi-directional.
I’ll be having a play soon 
Looks interesting @danbates, useful for emonDC? let us know how you get on
I think so… Testing and checking first. I’ll let you know.
Hi Dan, do you have any updates on the progress of the EmonDC? I am very interested as I would like to monitor the DC as well as the AC in my system.
Hi, It’s coming along slowly… There are safety related aspects which are worth getting certification for and I’m taking my time over them. I’ve made a couple of DC metering units by hand recently, both installed and working, sending to emonCMS. I used ABS enclosures to house them safely.
emonDC is some months down the road.
If you’d like to cover material cost I could assemble something for what you need.
Lets PM.
I’ve made a test of an ACS770.
I could only test with a small current for now. But it showed up! Worked fine, which was surprising. It was blasted by my too-hot gas torch and exuberant use of it.
I’ll be able to test again with a heftier source of current later this month.
When I started this thread, I knocked together a simple breakout board ACS7** series current sensors, in eagle, and sent it to ragworm.
Last week I put it together. A better soldering iron was what was needed to not repeat burning the board. I imagine a 40W iron would do the trick.
Here are a few pics. Send me a message if you’re interested in something like this. I’d like to gauge interest.
I’m repositioning the headers and mounts to make the breadboard rows more accessible and give the ring terminal mounts more space.
This is measuring current only.
I have 50 boards available for trying these out.
R1 is for voltage sensing, use with caution in regard to working voltages and floating grounds.
It’s sized for something like this.
See here for a farnell search showing the compatible ICs, 50A, 100A, 200A uni or bi-directional.
I noticed also not all of them have the same pinout! So check the datasheet for the right Vcc, Vout and GND pins.
£10 each ex delivery.
Please PM me if you’re interested.
For the uninitiated, what would you use these for?
They’re for developing a cheap current sensor module for DC. The bidirectional ones work for AC also, but we have the CTs here for doing that safely.
One of these modules could exist at the cable to be current-sensed, then a signal cable from the module to the logging device, whether that’s something in the shop here, hacked, or an Arduino, Nucleo, RPi with ADC… anything taking an analog signal.
A benefit of these hall-effect current sensors is isolation from the current carriers, protecting users from the generator’s voltage, touching the Vcc, Vout and GND lines of the device is safe. I think the isolation rating for these is 1.5kV minimum, some go to 3.5kV.
Other benefits are automatic temperature-compensation, accuracy and simplicity, the simplicity can mean reduced cost overall.
The main downside is the device is specified for a particular current range, so is not very flexible in that way.
Here’s a link to the github repo for this breakout.
. https://github.com/danbates2/emonDC/tree/master/hardware/ACS7**%20PFF%20Breakout
Hi Daniel,
That board looks great! I am trying to measure my solar and inverter power usage. I am preparing for the hurricane season here in the Caribbean (Puerto Rico) Do you still have boards available?
Thanks!
Hello Hector, welcome!
Yes! The boards are available with a kit in the shop.
If you want PCBs I could post some to you.
I have ring terminal connectors for them too.
Thank you Daniel,
I see that it includes a 50 amp sensor, do you have higher current sensors?
-Hector
Not yet, does this link work for you?
Any of these are fine. I could source some next week for you if you need.
Regards,
Dan
Hi Daniel,
Sorry I can’t work out how to private message you, and I’m aware this thread is old, but I hope you can help! I’ve been looking at using these ACS hall effect current sensors to measure DC currents coming from a solar array, and AC currents coming from a VFD, before feeding into a motor. (My research seems to show that CT sensors might not be able to cope at lower frequencies, and that the output of a VFD would have a lot of EMI noise due to the impure PWM signal. We’re looking at operating the VFD from 35Hz upwards).
I’ve found my biggest struggle with the ACS sensors is working out how to interface them with the solar array. The cables coming from the system are chunky 6mm cables designed to hold high currents. Soldering them directly to the legs of the sensor puts too much pressure on the smaller data legs and I’ve ended up snapping several off by accident. Your breakout board technique looks much neater. I’d be really interested in buying some if you have any more available. My biggest concern with some of the breakout boards I’ve seen so far is the termination methods. The small plastic screw down terminal blocks aren’t generally rated for high enough currents (and are often tiny in the ones I’ve seen), so I’m surprised to see them on breakout boards. Your breakboard board design looks like I would solder the cable directly, but even then I’m not sure how large a cable it could take? What cable size would you recommend with currents up to 50A AC? Or for 50A DC? I think ideally we’d eventually interface to a solar MC4 connector to easily and safely connect to and from our solar installations.
Really hope you can help! I’m been struggling on this problem for some months now, and feel I’m lacking the experience to know what is probably a great existing solution.
Thank you!
Natasha
Click on the user’s name, then click on the Message “button” in the dialog box that popped up.
Amazing thank you! I think as a super duper new user the feature hadn’t yet been granted to me when I first attempted to post
Correct. I bumped your user account up a level. You should be good to go now.
Hi Natasha,
I’m not super experienced myself, so all I can recommend is testing… a few thoughts…
The gerber files for the breakout board are available, and an order can be made with 2oz copper layer for better current handling. I did do this for the breakout boards above, but it’s been so long I don’t know where they are anymore. Not a single one sold… looking at the thread I can see the price was probably too high. Some test results and use cases would’ve helped too I’m sure.
I’ve put over a hundred amps r.m.s. through a similar design, using an arc welder, and that worked fine. The effects were observed with a thermal camera. It had 5mm bolts connecting ring terminals onto the hole mounts of the PCB.
If I remember right, this breakout has the same mountings.
Screw terminal mounts are surprisingly high current sometimes I agree! I can see I had the 10.16mm terminal block mount option on there. They are common at 76Amp rating. You might need to look at the safety margin or derating for your context, something perhaps @Robert.Wall can advise on, or check up in a design textbook.
The output signal of a bi-directional ACS series is mid-biased, probably has the frequency response suitable for your VFD (your upper limit?). The unidirectional ACS’s are around 0.5V above ground at zero amps. Calibration will be necessary… and maybe it’s worth checking for any significant phase shift of input/output at different frequencies if you’re comparing against a voltage signal.
