bidirectional dc current sensing with 358 or 324 op amp

[sahu]

any bode can help me about bidirectional dc current sensing with 358 or 324 op amp ? need its output read form mcu. i was try on Google , but not get it .

 

[MikeMl]

What current magnitude?

Can you break into the minus return lead into the power supply?

Can you devote two ADC channels (one for negative currents, one for positive current)?

 

[alec_t]

What mcu supply voltage?
Can you provide dual polarity supplies for the opamp?

 

[sahu]

i'm trying to do an amp meter with a shunt
I have need to read 50 amp DC. for inverter.
1- as on load ( when inverter on , now charging
off)
2- as on charging mode (now invereter
off ,charging on )
these reading read with 1 ADC .
not 2 ADC.

 

[alec_t]

It will help us to design something if you answer all the questions put to you. Please see post #3, and question 2 in post #2.

 

[sahu]

use like this

 

[KeepItSimpleStupid]

Not sure if it's one or two sensors, but I would not bother with the shunt approach. Use one of these: https://www.pololu.com/product/2199 The output is inherently isolated.

 

[sahu]

Not sure if it's one or two sensors, but I would not bother with the shunt approach. Use one of these: https://www.pololu.com/product/2199 The output is inherently isolated.

sir I have need it with op amp.
not any sencer.

 

[alec_t]

In your schematic, why are both inputs of both opamps connected to the same point?

 

[sahu]

In your schematic, why are both inputs of both opamps connected to the same point?

when invereter on current flow clock wise & when charging on current flow anticlock wise.

 

[Nigel Goodwin]

You're making it far too complicated - use a single opamp and bias it so zero current gives half voltage out, current one way will increase the voltage, current the other way will decrease it - one opamp, one adc, a little simple maths, no problem.

 

[sahu]

You're making it far too complicated - use a single opamp and bias it so zero current gives half voltage out, current one way will increase the voltage, current the other way will decrease it - one opamp, one adc, a little simple maths, no problem.

yes sir too complicated ,
when i usedit one by one ADC .is work fine
but when Add 2 pc IN 4148 diAod . its droped 0.350 volt on o\p terminal.
i use reff doc those AN1521 form microchip .
in this Atchment show only 1 part

 

[ronsimpson]

Assume: ADC range is 0 to 1V
Assume:Vref=1V
Want to measure +/- current.
(I think a gain of 100 is too large but)
R12 and R13 (2k and 2k) look like a 1k to 1/2 of Vref. (1k to 0.5V)
The amp has a gain of 100x. So a +/- 5mV signal will make a +/-500mV signal centered around 0.5V.

 

[dougy83]

Assume: ADC range is 0 to 1V
Assume:Vref=1V
Want to measure +/- current.
(I think a gain of 100 is too large but)
R12 and R13 (2k and 2k) look like a 1k to 1/2 of Vref. (1k to 0.5V)
The amp has a gain of 100x. So a +/- 5mV signal will make a +/-500mV signal centered around 0.5V.
View attachment 89230

The output of the opamp will be a negative voltage in the cct you provided. The positive reference voltage should be connected to the +ve input of the opamp.

 

[ronsimpson]

Yes Yes what was I thinking? Thank you Dougy83

 

[sahu]

Yes Yes what was I thinking? Thank you Dougy83
View attachment 89233

u tell me like this
so then this EQUATION is not for this sch
50A*0.005Ohm*2 = 1.25v

 

[dougy83]

Yes Yes what was I thinking? Thank you Dougy83
View attachment 89233

I think it's better to do it as shown in the following circuit. Zero amps gives ~2.5V out, -50 A --> 5 V out and +50 A --> 0 V out. Gain can be changed by changing R1.

 

[sahu]

I think it's better to do it as shown in the following circuit. Zero amps gives ~2.5V out, -50 A --> 5 V out and +50 A --> 0 V out. Gain can be changed by changing R1.
View attachment 89239

whats the EQUATION of this sch ?
Also tell me About v1 & v2.
v1 is those voltage , which Are develop here by current flow ?
v2 is reff voltage . I'm right ?

 

[dougy83]

whats the EQUATION of this sch ?

 

[sahu]

Iin = value of current flow
R1 = gain
20000 = ?
also tell me whats is v1 ?