Morning rajit,
What is the voltage value you have available for the negative supply.?
E

 

Morning rajit,
What is the voltage value you have available for the negative supply.?
E

dear eric,
7905,7912,7915,7924 all are available

 

hi,
This is one option using a -5V supply for the OPA's.
My only concern is that we are at the limits of the maximum power supply of the LM358, we have +24v and -5v == 29V total.
The LM358 is specified at 30V.
For the demo plot attached I have made the bridge voltage start at -0.1mV thru +3.6mV in order to show the Vout can be set to above or below zero, by using R18 trim pot.
Note: the 2N3819 is reconnected for the 4mA threshold.

E

 

hi,
This is one option using a -5V supply for the OPA's.
My only concern is that we are at the limits of the maximum power supply of the LM358, we have +24v and -5v == 29V total.
The LM358 is specified at 30V.
For the demo plot attached I have made the bridge voltage start at -0.1mV thru +3.6mV in order to show the Vout can be set to above or below zero, by using R18 trim pot.
Note: the 2N3819 is reconnected for the 4mA threshold.

E

dear eric,

i see the circuit. by using the R18 trim pot we can able to offset the OPA ?
i will check and get back you

thanks for your all time support.
R

 

Morning eric,

the negative supply i can give only at circuit testing level.
but once the circuit is finished, have to place it in a control panel and connect with PLC.
in control panel where there is only a +24 VDC power supply is available. at the time i cannot able to provide the negative supply.
sorry eric... i forget to consider this while i am selecting the negative supply.
now stand at last stage!!!

 

hi rajit,
You could consider a 15Vdc to 5Vdc Isolated DC2DC converter for -5V.

E

EDIT:
Example
https://www.reichelt.com/gb/en/?LAN...4tbrNlD67epn9oRONJQpL-bhkGHug0RoCf7UQAvD_BwE&

 

hi rajit,
You could consider a 15Vdc to 5Vdc Isolated DC2DC converter for -5V.

E

EDIT:
Example
https://www.reichelt.com/gb/en/?LAN...4tbrNlD67epn9oRONJQpL-bhkGHug0RoCf7UQAvD_BwE&

okay eric. i will check with it

 

hi,
There are wide range of modules avaiable, an Isolated 1 Watt version 15Vdc to 5Vdc would be a good choice.
When mounting the converter keep it away from the high gain/low level signal areas of the PCB and add decoupling caps, they can be a little electrically 'noisy'.
I have used them in many similar applications with no problems.
E