Hi everyone,
I'm working on a design in which I have multiple circuits for which I'm monitoring voltage as a means to detect state change of each circuit, specifically the state (open or closed) of the switch(es) on the circuit. At present the circuits share a common 12V DC source and are all grounded to the same grounding plane. Additionally the ICs I am using to enable/perform state change detection and voltage measurement (digipot, comparator, ADC) share the same 12V DC source and grounding plane though the source is stepped down to 5V and 3.3V via voltage dividers to supply the correct voltage for each IC.
I'm relatively new to hardware design though after the time i've spent learning I'm not surprised by the fact that I am seeing state changes in one or more circuits having an impact on the voltages i'm reading on the other circuits. I'm now looking at ways I can mitigate this such that the state changes on a circuit does not have an impact on the other circuits.
Using the diagram i've attached as a reference if the switch on Test Circuit 1 opens or closes I need to insure that the voltage on Test Circuit 2 and Test Circuit 3 does not change as a result.
Is the proper method for doing this to place an optoisolator between the 12V source and each circuit? Early on I had the supply and ground for the circuits on a separate supply/ground from the comparator, digipot and ADC and was not able to correctly measure voltages until I put them all on a common supply/ground. I'm curious if putting the optoisolator in place creates a situation where I need to put the comparator, digipot and ADC on the same, now isolated, supply/ground as each circuit or if there is something that I am missing.
Are there other options for keeping the circuits isolated but on a common supply/ground?
A couple of points about the diagram;
1. The portion of each circuit between the junction of each circuit to the 12V supply and the TVS are external to my device; my device provides the 12V on the "output" terminal and the "input" terminal begins just ahead of the TVS.
2. The external portion of each of these circuits may or may not include one or both of the external resistors and they may be anywhere from 0K to 5.6K ohm resistors; i've colored them red to indicate they may or may not be present and i've labeled them as Ext R# to denote they are external to my device. My device is designed to accommodate these variances.
Any advice or guidance is greatly appreciated.
thx - sean
I'm working on a design in which I have multiple circuits for which I'm monitoring voltage as a means to detect state change of each circuit, specifically the state (open or closed) of the switch(es) on the circuit. At present the circuits share a common 12V DC source and are all grounded to the same grounding plane. Additionally the ICs I am using to enable/perform state change detection and voltage measurement (digipot, comparator, ADC) share the same 12V DC source and grounding plane though the source is stepped down to 5V and 3.3V via voltage dividers to supply the correct voltage for each IC.
I'm relatively new to hardware design though after the time i've spent learning I'm not surprised by the fact that I am seeing state changes in one or more circuits having an impact on the voltages i'm reading on the other circuits. I'm now looking at ways I can mitigate this such that the state changes on a circuit does not have an impact on the other circuits.
Using the diagram i've attached as a reference if the switch on Test Circuit 1 opens or closes I need to insure that the voltage on Test Circuit 2 and Test Circuit 3 does not change as a result.
Is the proper method for doing this to place an optoisolator between the 12V source and each circuit? Early on I had the supply and ground for the circuits on a separate supply/ground from the comparator, digipot and ADC and was not able to correctly measure voltages until I put them all on a common supply/ground. I'm curious if putting the optoisolator in place creates a situation where I need to put the comparator, digipot and ADC on the same, now isolated, supply/ground as each circuit or if there is something that I am missing.
Are there other options for keeping the circuits isolated but on a common supply/ground?
A couple of points about the diagram;
1. The portion of each circuit between the junction of each circuit to the 12V supply and the TVS are external to my device; my device provides the 12V on the "output" terminal and the "input" terminal begins just ahead of the TVS.
2. The external portion of each of these circuits may or may not include one or both of the external resistors and they may be anywhere from 0K to 5.6K ohm resistors; i've colored them red to indicate they may or may not be present and i've labeled them as Ext R# to denote they are external to my device. My device is designed to accommodate these variances.
Any advice or guidance is greatly appreciated.
thx - sean