high-side current sensor...

[Lasse Langwadt Christensen]

tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:

On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com
wrote:
On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents ...

So, is this regulated voltages, nine of \'em, and you want the output currents
from nine low-V regulators, or is it input to the regulators, and is that input somewhere
in the vicinity of 48VDC? Are these nine currents going to include initial
charging of filter capacitors? How big are those capacitors? Are some of the
regulators switchers?

As for \'intelligent cutoffs\', do you want to do that at the high-side? A secondary
low-current power supply grounded at the high rail might be economic, if
you want to have nine sensors and nine cutoffs all near the +48V source.
There will be eight user-programmable power supplies, each running off
+48, all off a common +48 bus fed from a kilowatt bulk power supply.
Users can potentially install modules and program and load the
supplies such as to cave in the main source, which would be really
ugly. That\'s against the rules in the manual, but we need to protect
things if they do it.

there is quite a few high side load switches with short circuit protection
and a combined current monitor / error output , but I think most of them
are limited to a ~24V supply

 

[whit3rd]

On Monday, January 10, 2022 at 8:26:05 PM UTC-8, gnuarm.del...@gmail.com wrote:

On Monday, January 10, 2022 at 10:39:34 PM UTC-5, DJ Delorie wrote:
I was going to suggest the INA139 (which I\'ve used) but it only goes to 40v...

The LT6106 is an easy to use device, but again, 36 volts only. ...
Know any good opamps that work up to 48 volts?

Instead of buying nine HV (instrument or op)-amp chips, use any-old-one, and a resistor-zener-capacitor to
bias nine transistors with suitable ratings in cascode.

Actually, since this is average-current (heat, really) related, you can probably dawdle a bit;
maybe just use that zener supply to do current/frequency converters, and
then nine capacitors will do all the level translation required; it just takes a count-and-average
bit of hardware at the logic-level to complete the sensing.

 

[John Larkin]

On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com
wrote:
On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents ...

So, is this regulated voltages, nine of \'em, and you want the output currents
from nine low-V regulators, or is it input to the regulators, and is that input somewhere
in the vicinity of 48VDC? Are these nine currents going to include initial
charging of filter capacitors? How big are those capacitors? Are some of the
regulators switchers?

As for \'intelligent cutoffs\', do you want to do that at the high-side? A secondary
low-current power supply grounded at the high rail might be economic, if
you want to have nine sensors and nine cutoffs all near the +48V source.
There will be eight user-programmable power supplies, each running off
+48, all off a common +48 bus fed from a kilowatt bulk power supply.
Users can potentially install modules and program and load the
supplies such as to cave in the main source, which would be really
ugly. That\'s against the rules in the manual, but we need to protect
things if they do it.

there is quite a few high side load switches with short circuit protection
and a combined current monitor / error output , but I think most of them
are limited to a ~24V supply

The c code can shut down supply modules as needed. Each power supply
module has its own FPGA that the main controller can address. There\'s
no need to actually remove 48v power from the baby boards. The master
controller just needs to know the currents and have some reasonable
rules.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Lasse Langwadt Christensen]

tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:

On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com
wrote:
On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents ...

So, is this regulated voltages, nine of \'em, and you want the output currents
from nine low-V regulators, or is it input to the regulators, and is that input somewhere
in the vicinity of 48VDC? Are these nine currents going to include initial
charging of filter capacitors? How big are those capacitors? Are some of the
regulators switchers?

As for \'intelligent cutoffs\', do you want to do that at the high-side? A secondary
low-current power supply grounded at the high rail might be economic, if
you want to have nine sensors and nine cutoffs all near the +48V source.
There will be eight user-programmable power supplies, each running off
+48, all off a common +48 bus fed from a kilowatt bulk power supply.
Users can potentially install modules and program and load the
supplies such as to cave in the main source, which would be really
ugly. That\'s against the rules in the manual, but we need to protect
things if they do it.

there is quite a few high side load switches with short circuit protection
and a combined current monitor / error output , but I think most of them
are limited to a ~24V supply
The c code can shut down supply modules as needed. Each power supply
module has its own FPGA that the main controller can address. There\'s
no need to actually remove 48v power from the baby boards. The master
controller just needs to know the currents and have some reasonable
rules.

check.

depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?

 

[Three Jeeps]

On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:

We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye

I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J

 

[Flyguy]

On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:

On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye
I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J

The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf

 

[Lasse Langwadt Christensen]

onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:

On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye
I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J
The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf

also much much more expensive than a current sense amplifier

 

[John Larkin]

On Tue, 11 Jan 2022 16:25:41 -0800 (PST), Three Jeeps
<jjhudak4@gmail.com> wrote:

On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye

I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J

If a data sheet looks clear, I wouldn\'t test the part.

We have room to put two different highside chips on the PCB and just
stuff the one we can get. TI and ADI maybe.



--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[server]

On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com
wrote:
On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents ...

So, is this regulated voltages, nine of \'em, and you want the output currents
from nine low-V regulators, or is it input to the regulators, and is that input somewhere
in the vicinity of 48VDC? Are these nine currents going to include initial
charging of filter capacitors? How big are those capacitors? Are some of the
regulators switchers?

As for \'intelligent cutoffs\', do you want to do that at the high-side? A secondary
low-current power supply grounded at the high rail might be economic, if
you want to have nine sensors and nine cutoffs all near the +48V source.
There will be eight user-programmable power supplies, each running off
+48, all off a common +48 bus fed from a kilowatt bulk power supply.
Users can potentially install modules and program and load the
supplies such as to cave in the main source, which would be really
ugly. That\'s against the rules in the manual, but we need to protect
things if they do it.

there is quite a few high side load switches with short circuit protection
and a combined current monitor / error output , but I think most of them
are limited to a ~24V supply
The c code can shut down supply modules as needed. Each power supply
module has its own FPGA that the main controller can address. There\'s
no need to actually remove 48v power from the baby boards. The master
controller just needs to know the currents and have some reasonable
rules.

check.

depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?

Looks like we can use the XADC in the Zynq, the main controller FPGA.
That\'s a 1-volt full-scale, pretty terrible ADC. The voltage drop
across a shunt might be 50 mV with a common-mode of 48 volts. So we
need some sort of high-side amp.

A flying capacitor mux would be fun, but too slow. And a dual SSR
would cost more than a current sense chip.





--

I yam what I yam - Popeye

 

[ke...@kjwdesigns.com]

On Tuesday, 11 January 2022 at 17:21:32 UTC-8, John Larkin wrote:
....

If a data sheet looks clear, I wouldn\'t test the part.

We have room to put two different highside chips on the PCB and just
stuff the one we can get. TI and ADI maybe.
--

....
I like the LTC6102.

It\'s not as cheap as some of the other solutions but has a very low offset voltage so the burden (and power dissipation in the shunt) can be very low. The architecture is the same as many others using a P-channel FET.

The vanilla one can tolerate 70v surges and there is a 100V part available as well. I\'m using it in an automotive 48V design where surge tolerance is vital as well as automotive qualified.

kw

 

[server]

On Mon, 10 Jan 2022 19:26:09 -0800, jlarkin@highlandsniptechnology.com
wrote:

We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.

https://wolfstreet.com/2022/01/12/after-the-shortage-a-glut-semiconductor-sales-hit-record-for-7th-month-hundreds-of-billions-in-new-investments-planned/

I\'m guessing that

Cars use a lot of high-side current sensors

and

The semi shortage/glut cycle is swinging up

and

China is scary.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

Lasse Langwadt Christensen wrote:

onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye
I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J
The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf

also much much more expensive than a current sense amplifier

Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
nine quad pack resistors would do it too.

Alternatively, a regular resistive diff amp using your garden variety op
amp and a decent quad pack could run off +26V and ground, say. With
unity gain, the output is near ground and the inputs are near +24V.
You\'d have some offset due to resistor mismatch, but nothing horrible.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Lasse Langwadt Christensen]

onsdag den 12. januar 2022 kl. 02.21.32 UTC+1 skrev John Larkin:

On Tue, 11 Jan 2022 16:25:41 -0800 (PST), Three Jeeps
jjhu...@gmail.com> wrote:

On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye

I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J
If a data sheet looks clear, I wouldn\'t test the part.

We have room to put two different highside chips on the PCB and just
stuff the one we can get. TI and ADI maybe.

yeh, at the moment it makes sense to practice \"defensive design\" with multiple options

 

[Jan Panteltje]

On a sunny day (Wed, 12 Jan 2022 08:09:56 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
<d7vttgldb6quk5stq411h5af307oi59a9o@4ax.com>:

On Mon, 10 Jan 2022 19:26:09 -0800, jlarkin@highlandsniptechnology.com
wrote:

We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.

https://wolfstreet.com/2022/01/12/after-the-shortage-a-glut-semiconductor-sales-hit-record-for-7th-month-hundreds-of-billions-in-
new-investments-planned/

I\'m guessing that

Cars use a lot of high-side current sensors

and

The semi shortage/glut cycle is swinging up

and

China is scary.

Oh, and there is an other solution
Make a nice front panel with some of these for example:
https://www.ebay.com/itm/262960322005
there are cheaper ones from < 5 $, I use some with the Meanwells.
Now you have a nice user interface.
Then use a webcam and write the 7 segment number decoder, like I did:
http://panteltje.com/panteltje/7s_parser/index.html
digital clock time numbers to stdout:
https://www.youtube.com/watch?v=sDYmW6swL-M
pipe it through for example wcalc in Linux to do math with it and control things.
Why do it simple if you can do it complicated?
But actually there is a large application area to read instrument panels.


Was just one of those wild ideas, \'lemme try this\'.
So simple..

 

[Klaus Vestergaard Kragelund]

On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:

On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

jlarkin@highlandsniptechnology.com> wrote:

We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.

Current mirror using pairs of high voltage PNP transistors?

I just posted something like that. It should be good enough. If the
voltage drop across Q2 is pitched a little high, so there is a little
positive measurement offset, we can math that out.

A single current sense amp, but switched to the different sense
resistors with a 50V ana mux. Syncronized to the ADC sampling

 

[John Larkin]

On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

jlarkin@highlandsniptechnology.com> wrote:

We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.

Current mirror using pairs of high voltage PNP transistors?

I just posted something like that. It should be good enough. If the
voltage drop across Q2 is pitched a little high, so there is a little
positive measurement offset, we can math that out.



A single current sense amp, but switched to the different sense
resistors with a 50V ana mux. Syncronized to the ADC sampling

We could mux on the high side, with a cheap 4051 type mux. We\'d need a
highside power supply, just a zener, and some way to translate the mux
address lines.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[whit3rd]

On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:

Lasse Langwadt Christensen wrote:

also much much more expensive than a current sense amplifier

Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
nine quad pack resistors would do it too.

True; that\'s only the first step, though, it just makes a ground-referenced signal,
and next step is an ADC. Trouble is, this is a power signal, with surges expected,
so the sampling due to an ADC is problematic. Since low-power-using modules aren\'t the
most important to get accurate readings on, I\'d note that an eightpack of VCOs
can deliver pulse streams that don\'t ignore any of the abrupt changes in their inputs,
and at the ground-referenced end it just takes counter inputs to digitize the averages
over any convenient period. Ten kilohertz center frequency, half-second average period,
beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...

A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You\'d
want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
Vdd for the \'555.

Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.

 

[Lasse Langwadt Christensen]

onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:

On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
Lasse Langwadt Christensen wrote:

also much much more expensive than a current sense amplifier

Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
nine quad pack resistors would do it too.
True; that\'s only the first step, though, it just makes a ground-referenced signal,
and next step is an ADC. Trouble is, this is a power signal, with surges expected,
so the sampling due to an ADC is problematic. Since low-power-using modules aren\'t the
most important to get accurate readings on, I\'d note that an eightpack of VCOs
can deliver pulse streams that don\'t ignore any of the abrupt changes in their inputs,
and at the ground-referenced end it just takes counter inputs to digitize the averages
over any convenient period. Ten kilohertz center frequency, half-second average period,
beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...

A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You\'d
want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
Vdd for the \'555.

Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.

the Zynq ADC is 1MSPS ...

 

[server]

On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
Lasse Langwadt Christensen wrote:

also much much more expensive than a current sense amplifier

Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
nine quad pack resistors would do it too.
True; that\'s only the first step, though, it just makes a ground-referenced signal,
and next step is an ADC. Trouble is, this is a power signal, with surges expected,
so the sampling due to an ADC is problematic. Since low-power-using modules aren\'t the
most important to get accurate readings on, I\'d note that an eightpack of VCOs
can deliver pulse streams that don\'t ignore any of the abrupt changes in their inputs,
and at the ground-referenced end it just takes counter inputs to digitize the averages
over any convenient period. Ten kilohertz center frequency, half-second average period,
beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...

A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You\'d
want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
Vdd for the \'555.

Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.

the Zynq ADC is 1MSPS ...

And kinda nasty. But we can scan fast and do a bit of signal averaging
in the FPGA. I only need the current measurements every millisecond,
to do my shutdown protection logic.

Exponential smoothing (1st order lowpass) is easy

Vout = Vout + (Vin-Vout) * K with smallish K

but my FPGA kids will probably want to do something fancier.



--

I yam what I yam - Popeye

 

[Flyguy]

On Tuesday, January 11, 2022 at 5:19:34 PM UTC-8, lang...@fonz.dk wrote:

onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
We\'ll have a 48 volt, 20 amp power supply that feeds eight plug-in
modular load boards. We want to measure all 9 currents so that we can
do some sorts of intelligent cutoffs if the eight boards threaten to
cave in the big supply.

So we want nine mediocre-accuracy unipolar high-side current sensors
so we can digitize the currents with a grounded mux/adc.

Does anyone have a favorite but cheap high-side current sense IC?

We can add shunts, or I guess it could be some Hall thing.



--

I yam what I yam - Popeye
I\'ve used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
https://www.digikey.com/catalog/en/partgroup/current-monitor/19066

Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
J
The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
also much much more expensive than a current sense amplifier

Well, you might actually compare prices of a working circuit to the AD8479. I don\'t think you can.