IC to measure voltage/current on amp rails?
Hello,
Has anyone ever monitored the rail(s) current and voltage of a solid state amplifier via a microcontroller? Is there a suitable IC with either an analogue or I2C output that can be used? I assume such a device wouldn't impact the sound in any way?
Thank you in advance,
Ian
Hello,
Has anyone ever monitored the rail(s) current and voltage of a solid state amplifier via a microcontroller? Is there a suitable IC with either an analogue or I2C output that can be used? I assume such a device wouldn't impact the sound in any way?
Thank you in advance,
Ian
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TI has an amp chip with I/V monitoring built in but its not in a DIY friendly package.
For current monitoring on a high voltage rail you can use http://www.ti.com/lit/ds/symlink/ina138.pdf
For current monitoring on a high voltage rail you can use http://www.ti.com/lit/ds/symlink/ina138.pdf
Yes I'd imagine chip amps could/would have such features built in. However, for me I'm building an amp from the forum and thought it would be interesting to see how the voltage and current changed on each rail during normal use.
The INA168 looks suitable given my rails are +- 42v. To measure the negative rail I assume one just reverses the vin+ and vin- connections?
There are AC power measurement ICs that I know of with an I2C output but not sure if there is a DC equivalent version!?
The INA168 looks suitable given my rails are +- 42v. To measure the negative rail I assume one just reverses the vin+ and vin- connections?
There are AC power measurement ICs that I know of with an I2C output but not sure if there is a DC equivalent version!?
I don't believe the INA168 is set up to operate on the low side. I'd suggest rolling your own voltage-current converter for that out of an opamp whose inputs can operate at neg rail CM voltage and a MOSFET.
Hello,
You have this kind of circuit:
- ACS712 Module Measures Currents up to 30A for as Low as $1 Shipped
You have this kind of circuit:
- ACS712 Module Measures Currents up to 30A for as Low as $1 Shipped
No need for a function specific IC, just design yourself the circuit you need to allow those parameters to be presented to the microprocessor.
I suppose it can measure and handle an analog voltage from 0 to 5V DC ; if not add whatever´s needed for that, I guess some kind of analog to digital converter.
Once you solve that, you turn anything you need to measure into a voltage varying between 0 and 5V DC.
1) +V rail.
You have around +42V?
Ok, a 20:1 attenuator , roughly 22k+1k will give you around 2V DC ... input that into your ADC>microprocessor and do whatever you want.
2) -V rail: same thing, only the negative voltage goes into a unity gain inverting Op Amp , now you have positive 2V instead of negative 2V, do the same thing but "tell" the microprocessor that such voltage is actually negative.
3) rail current: insert a low value resistor in series with each rail and measure voltage drop across it ; 0.1 ohms will give you 100mV per Ampere.
Again feed that to microprocessor, with the caveat that said measurement voltages will be floating *42V and -42V from ground (same will happen with any dedicated "measurement" IC if you find one) but there are "level shifting" circuits which allow you to send far away floating voltages to ground referenced circuits.
All this is standard Analog Electronics, not sure how much of it is being taught nowadays, I studied Engineering from 1969 to 1975 and maybe nowadays Analog is only briefly mentioned before getting full speed into Digital.
EDIT: just checked the INA datasheet, it´s eactly the same I´m suggesting to measure current, including the series sensing resistor and the "level shifting" voltage to current conversion, to be converted again to voltge referred to ground, only in a pre built package for user convenience.
What I suggest takes a little elbow grease in designing and building but can be scaled for *any* voltage and current and also adapted for negative rails.
Well, the difference between home cooking from scratch and reheating a "TV dinner" in the microwave 🙂
I suppose it can measure and handle an analog voltage from 0 to 5V DC ; if not add whatever´s needed for that, I guess some kind of analog to digital converter.
Once you solve that, you turn anything you need to measure into a voltage varying between 0 and 5V DC.
1) +V rail.
You have around +42V?
Ok, a 20:1 attenuator , roughly 22k+1k will give you around 2V DC ... input that into your ADC>microprocessor and do whatever you want.
2) -V rail: same thing, only the negative voltage goes into a unity gain inverting Op Amp , now you have positive 2V instead of negative 2V, do the same thing but "tell" the microprocessor that such voltage is actually negative.
3) rail current: insert a low value resistor in series with each rail and measure voltage drop across it ; 0.1 ohms will give you 100mV per Ampere.
Again feed that to microprocessor, with the caveat that said measurement voltages will be floating *42V and -42V from ground (same will happen with any dedicated "measurement" IC if you find one) but there are "level shifting" circuits which allow you to send far away floating voltages to ground referenced circuits.
All this is standard Analog Electronics, not sure how much of it is being taught nowadays, I studied Engineering from 1969 to 1975 and maybe nowadays Analog is only briefly mentioned before getting full speed into Digital.
EDIT: just checked the INA datasheet, it´s eactly the same I´m suggesting to measure current, including the series sensing resistor and the "level shifting" voltage to current conversion, to be converted again to voltge referred to ground, only in a pre built package for user convenience.
What I suggest takes a little elbow grease in designing and building but can be scaled for *any* voltage and current and also adapted for negative rails.
Well, the difference between home cooking from scratch and reheating a "TV dinner" in the microwave 🙂
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Hi,
I used the ACS7XX as alayn91 mentioned. Easy to use and the best of it is that it is isolated from the output no inference with the sound. There are different sizes from 5 amps to 200 amps. Just connect it in series with the speaker output.
I used the ACS7XX as alayn91 mentioned. Easy to use and the best of it is that it is isolated from the output no inference with the sound. There are different sizes from 5 amps to 200 amps. Just connect it in series with the speaker output.
Check out the ltc2975, it's a little expensive but does so much. Simple voltage dividers can be used for rail voltage measurement. You'll need current sense amps to measure rail currents (lt6101 6105) which take a differential voltage across a sense element and drive it's output single ended. I suggest 1 to 10 mohm which will give enough "signal" yet not too high for currents up to 50A. LTC provides a free download for the GUI, LTpowerplay. You'll need windows to run it.
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