eem2am
Banned
serial communication opto
Hello,
Please can you help me to correct where I went wrong with this interview question concerning serial data transmission over some distance, with a single comms line (eg not twisted pair) ?
There is also opto-isolation of the sender from the receiver.
The interviewer did not say exactly how far the data was being sent….but he said that sender and receiver had “some distance” between them………-since they were talking about electronic systems aboard auto-mobiles, I think its safe to assume that he meant that the signal was being sent from one part of a car or truck to another part of the same car/truck.
The interviewer also stated that there were bad electrical noise problems in the environment.
The interviewer also stated that signal isolation was needed….so I suggested using pulse-transformers, but the interviewer said I must use opto-isolation.
Anyway, I stated that I would want to use shielded twisted pair or co-axial cable…
-But he insisted that we had to consider a SINGLE comms line for the serial data…..
…….this was the diagram that we drew together of the system…….i basically drew the opto-coupler bit, since he asked me to do that………..
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
I appreciate that the above diagram may look a bit unusual to readers?…….
-but this is the diagram that the interviewer asked me to consider……..
-During the interview, I presumed that the DPST switch was just like a representative way of showing that it can send pulses.
Anyway………..
The interviewer referred me to the above diagram, -and told me that it was a very electrically noisy environment.
-The interviewer then asked me how I would deal with such noise.
-I told him that I would filter it out.
-He then asked me to demonstrate how I would filter the noise out.
……so I drew in the capacitor as follows…………
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
-Include Filter cap
Its only now that I realise that my placement of the cap in the above position was incredibly stupid.
-Little wonder that the interview was terminated soon after this.
Would you agree that the cap should have been placed across the following position ?…….
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
-Include Filter cap in better (?) position.
Also, have you ever heard of this kind of “single-line” communication?……….i thought that ‘go’ and ‘return’ should be as close as possible?….eg, as in twisted pair?
Do you believe that I should have filtered the noise with a common-mode-choke ?
Or do you know how I should have gone about filtering the noise?
Hello,
Please can you help me to correct where I went wrong with this interview question concerning serial data transmission over some distance, with a single comms line (eg not twisted pair) ?
There is also opto-isolation of the sender from the receiver.
The interviewer did not say exactly how far the data was being sent….but he said that sender and receiver had “some distance” between them………-since they were talking about electronic systems aboard auto-mobiles, I think its safe to assume that he meant that the signal was being sent from one part of a car or truck to another part of the same car/truck.
The interviewer also stated that there were bad electrical noise problems in the environment.
The interviewer also stated that signal isolation was needed….so I suggested using pulse-transformers, but the interviewer said I must use opto-isolation.
Anyway, I stated that I would want to use shielded twisted pair or co-axial cable…
-But he insisted that we had to consider a SINGLE comms line for the serial data…..
…….this was the diagram that we drew together of the system…….i basically drew the opto-coupler bit, since he asked me to do that………..
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
I appreciate that the above diagram may look a bit unusual to readers?…….
-but this is the diagram that the interviewer asked me to consider……..
-During the interview, I presumed that the DPST switch was just like a representative way of showing that it can send pulses.
Anyway………..
The interviewer referred me to the above diagram, -and told me that it was a very electrically noisy environment.
-The interviewer then asked me how I would deal with such noise.
-I told him that I would filter it out.
-He then asked me to demonstrate how I would filter the noise out.
……so I drew in the capacitor as follows…………
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
-Include Filter cap
Its only now that I realise that my placement of the cap in the above position was incredibly stupid.
-Little wonder that the interview was terminated soon after this.
Would you agree that the cap should have been placed across the following position ?…….
***DIAGRAM OF “SINGLE LINE” SERIAL COMMS WITH OPTO ISOLATION
-Include Filter cap in better (?) position.
Also, have you ever heard of this kind of “single-line” communication?……….i thought that ‘go’ and ‘return’ should be as close as possible?….eg, as in twisted pair?
Do you believe that I should have filtered the noise with a common-mode-choke ?
Or do you know how I should have gone about filtering the noise?