Current transformer to Hall effect sensor.

Got a hardware problem? ask for help

Current transformer to Hall effect sensor.

Postby dnbdubs3800 » August 2nd, 2017, 5:20 am

Please excuse me as I'm so out of touch. I have 2000 devices from a building management system that reads current using a current transformer to tell if some emergency lights are working. Now they have been upgraded to led these modules need to be able read dc current. I'm looking for ideas on how to use a hall effect sensor in place of the CT it looks like the units just take the ac current and rectifys and uses a shunt resistor to go to the adc on a pic chip. Image attached
dnbdubs3800
 
Posts: 4
Joined: August 2nd, 2017, 5:10 am

Re: Current transformer to Hall effect sensor.

Postby k-ww » August 3rd, 2017, 11:23 am

There are chips that have a isolated sense wire to carry the current, and an integrated hall sensor to measure the resultant current.

You would wire the chip in place of the current transformer and connect the output to the PIC [after scaling the output.

To better help you, I need the current range you are trying to measure.

Your pix did not go thru.
User avatar
k-ww
 
Posts: 1286
Joined: February 17th, 2011, 10:47 am

Re: Current transformer to Hall effect sensor.

Postby dnbdubs3800 » August 5th, 2017, 6:44 pm

The current for half will be 40milli amps and the other 10milli amps. The original ac current was around 160milli amps. The CT had a ratio of 1/5. Successfully attached the image this time. Many thanks.
Attachments
_20170806_014359.JPG
dnbdubs3800
 
Posts: 4
Joined: August 2nd, 2017, 5:10 am

Re: Current transformer to Hall effect sensor.

Postby k-ww » August 7th, 2017, 10:53 am

If you post a pix of the bottom of the PCB, and the part #'s of the chips besides the two PIC micros, I can figure out the circuit of the board.
User avatar
k-ww
 
Posts: 1286
Joined: February 17th, 2011, 10:47 am

Re: Current transformer to Hall effect sensor.

Postby dnbdubs3800 » August 9th, 2017, 6:11 am

Many thanks,

The first black one is ts922in op amp. The second is a 4n35 optocoupler. The pic next to the op amp is 12c671/p and the other responsible for the BMS protocol is a 12c509a.
Attachments
_20170809_130726.JPG
dnbdubs3800
 
Posts: 4
Joined: August 2nd, 2017, 5:10 am

Re: Current transformer to Hall effect sensor.

Postby dnbdubs3800 » August 18th, 2017, 4:01 am

I've actually managed to make it work without a hall effect sensor as the current I'm reading is so small I've wired a shut resistor between the two terminals and the BMS software recognises the current flowing at a safe level
dnbdubs3800
 
Posts: 4
Joined: August 2nd, 2017, 5:10 am

Re: Current transformer to Hall effect sensor.

Postby k-ww » August 18th, 2017, 5:37 am

Way to go!

Now all you have to do is repeat the mod 2000 times ;-)
User avatar
k-ww
 
Posts: 1286
Joined: February 17th, 2011, 10:47 am


Return to Help me! Hardware

Who is online

Users browsing this forum: No registered users and 2 guests