ADS1115 fried twice :-(

Hi,

I have a 50 Amps 75mV current shunt (in a 12V line) with an ADS1115 amplifier hooked up to an arduino.

I now fried two ADS1115 boards :frowning: (smoke visible...).

First time I had VDD connected to 5V and read somewhere it should be 3,3. Changed it (and without A0 and A1 connected) it worked. When I connected A0 and A1 it again immediately fried the chip...

I thought I had it connected correctly...


Not sure why it does not show the image... : Dropbox - File Deleted

Any Ideas?

Regards,
Jeroen

Well then how did you connect it? And what board is this exactly?

Hang on - 12V?? No chance, its a 5V max chip.

Perhaps you are wanting a high-side current sense module like this:
https://www.coolcomponents.co.uk/attopilot-voltage-and-current-sense-breakout-90a.html

it's a 16 bit ADC

and I thought I was measuring a differential signal ( so max 75 mV over the shunt...).

I added a link to a quick sketch of the connections. (it seems an image link to a dropbox does not work...)

ow, I think I know what I did wrong.

I should have put the shunt after the load in the ground in stead of before the load...

would appreciate if somebody can confirm this is the error preventing me from toasting more IC's :slight_smile:

thx,
Jeroen

16bit ain't the same as 16v

The a0 and a1 pins can only take within .3v of vdd (5v)

http://www.ti.com/lit/ds/sbas444b/sbas444b.pdf

Maybe you need a voltage devider?

vorstendom:
I have a 50 Amps 75mV current shunt (in a 12V line) with an ADS1115 amplifier hooked up to an arduino.
I now fried two ADS1115 boards :frowning: (smoke visible...).

You have just discovered that shunt voltage has to stay withing the supply extremes of the A/D converter.

Even with the shunt in the ground line, and a differential hookup, you can only measure positive voltages.

Maybe you should use an INA219 breakout board (Adafruit/ebay).
Voltage, high-side bi-directional current, PGA, and 12-bit A/D, all in one.
Just connect the onboard 0.1ohm shunt (current inputs) to the external shunt.
Leo..

thx for the feedback.

Yes I know 16 bit is not 16V I am just a bit of an electronic noob :slight_smile:
But I now do understand why it fried hooking up more than .3+VDD.

@MarkT, I did look at boards like you linked to but I am going to use it in a camper and using a 750W 12V DC to 220AC converter I can get up to 60 amps or so and even though for some of those breakout boards it is within specs I trust a shunt more than such a small breakout board with those kind of amps.

@Wawa, Thx for the INA219 tip. I will order one and see how it works. It has more functionality but it is also more expensive and I do not understand what exactly are the benefits if I only would measure the amps through a shunt.
later I will also hook up a solar panel (with a converter) to charge the battery. I thought that would give me negative differential voltage so that I can measure what is used but also what is charged. Is this not correct?

thx!

Yes. The INA219 bi-directional. Charging and discharging.
The advantage of measuring high-side (in the + line) is that you don’t have to break ground (with a shunt).
A shunt in the ground wire could give all sorts of problems.
Leo…

vorstendom:
it's a 16 bit ADC

and I thought I was measuring a differential signal ( so max 75 mV over the shunt...).

I added a link to a quick sketch of the connections. (it seems an image link to a dropbox does not work...)

Taking any input outside the supply range of a chip fries it , the anti-static diodes must have
vaporized instantly in your setup as you had many amps available! That probably saved your Arduino
from being destroyed too.