bidirectional dc current sensing with 358 or 324 op amp

[dougy83]

normally adc reading are as

result = 0;
for (i=0;i<20;i++)
{ set_adc_channel(0);
delay_ms(1);
result=result+read_adc(); 
result = result/20 ; }

if its right

If you're trying to oversample the ADC reading, that is not the way to do it: you should only divide the result sum by 20 once, outside the loop.

 

[sahu]

If you're trying to oversample the ADC reading, that is not the way to do it: you should only divide the result sum by 20 once, outside the loop.

then, whats the best method for its ADC reading ?

 

[sahu]

what u say about this sch ?

when i use this sch it , but found IN4148 drooped 0.350 volt then , our gain formula whats ?
have u any guidance for it , those help me lot
sorry my bad English .

 

[ronsimpson]

1) Your circuit will have one diode drop of error. If you use two op-amplifiers to do this job you need the diode inside the feedback loop.
2) You can measure the voltage 1000/second and do the rectification in software. (no diodes)

 

[sahu]

1) Your circuit will have one diode drop of error. If you use two op-amplifiers to do this job you need the diode inside the feedback loop.
2) You can measure the voltage 1000/second and do the rectification in software. (no diodes)

sir g
1 :--) when 1 opamp give reading(in +ve volt) then that time other opamp give reading(in -ve volt). so its region i used 2 IN4148 diode inside.

2 :--) i cont understand measure the voltage 1000/second and do the rectification in software. pl giv me a exampol

 

[ronsimpson]

2) No op-amps. Above we talked about a current sensor that has a output of 1/2 of your reference voltage when there is zero current.
Zero voltage is a large current. Vref= a large current.
ADC reading in 8 bit math, signed 8 bit.
0000 0000 = maximum current (+)
0111 1111 = very small current
1000 0000= very small current
1111 1111= maximum current (-)

Next find absolute value. ( you have only positive numbers)

With simple math you can find, peak, average, RMS, any thing you want.

You can do this math.