Am trying to create a cable fault decector, i plan to do this by building a pusle generator and sending pulses through the cable, and calculating the time it takes to return if there is a fault, would anyone be able to recommend a micro controller or arduino as I have experience working with them, that has a high sampling rate which will be able to collect the data from the returing pulses. as ones Ive looked at have been too slow.

Many thanks, any other advice on the project is welcome aswell.

 

Have you done that with an oscilloscope yet?? I read about a simple cable fault "Time Domain Reflectometer" built from free fast logic ICs. The article showed the reflected pulse, and it seems that they are neither all the same nor that similar. Also, the pulses are quite low amplitude, so that a lot of gain is required.
My point being that accurately evaluating a returned pulse with a micro may be rather difficult. And unless you know the propagation velocity in the cable being checked it will be quite a challenge to get an accurate distance measurement.

 

If you only want to detect the returned pulse, arduino will do,
If you looking to detect a reflection of a fault in the cable, then that's a tdr,
Look at speed of pulse in cable,
300mm per ns, as a start,
If you want to tell within 300mm where the fault is, you need a resolution of at least 1 Ghz, preferably 10 Ghz,
That's not a small microcontroller,
But a 1000 dollar adc
You also need to generate a very fast pulse edge, Into a capacitive cable load, that's not a logic output , but a rf driver chip,

 

Have you done that with an oscilloscope yet?? I read about a simple cable fault "Time Domain Reflectometer" built from free fast logic ICs. The article showed the reflected pulse, and it seems that they are neither all the same nor that similar. Also, the pulses are quite low amplitude, so that a lot of gain is required.
My point being that accurately evaluating a returned pulse with a micro may be rather difficult. And unless you know the propagation velocity in the cable being checked it will be quite a challenge to get an accurate distance measurement.

i see, i may need to look into other ways then, as the project just states to build a cable fault detector which I need to apply a short pulse to the cable and measuring reflections from the fault. This would be based on simple transmission line theory.
I guess I could use aa oscilloscope, although I havnt much experience with them, I need to be able to have the distance shown on a monitor, is there a way to connect a oscilloscope to my board and then display the data?

 

i see, i may need to look into other ways then, as the project just states to build a cable fault detector which I need to apply a short pulse to the cable and measuring reflections from the fault. This would be based on simple transmission line theory.
I guess I could use aa oscilloscope, although I havnt much experience with them, I need to be able to have the distance shown on a monitor, is there a way to connect a oscilloscope to my board and then display the data?

First, should those be in home work help section, also for high school projects,
Second, do a Google for tdr, time domain reflectomiteres

 

Welcome to AAC!

as the project just states to build a cable fault detector which I need to apply a short pulse to the cable and measuring reflections from the fault.

Is this schoolwork?

I guess I could use aa oscilloscope, although I havnt much experience with them,

That's how engineers have been doing it for decades.

 

Welcome to AAC!
Is this schoolwork?
That's how engineers have been doing it for decades.

hi yes, this is for school.

 

Am trying to create a cable fault decector, i plan to do this by building a pusle generator and sending pulses through the cable, and calculating the time it takes to return if there is a fault, would anyone be able to recommend a micro controller or arduino as I have experience working with them, that has a high sampling rate which will be able to collect the data from the returing pulses. as ones Ive looked at have been too slow.

Many thanks, any other advice on the project is welcome aswell.

It's possible to measure the delay (indirectly with a ADC measuring the linear change in voltage from a timed constant current source) with a PIC controller module called the CTMU if you want the display on the controller to show the data. You still will need the transmission line front-end logic to transmit and receive the pulse. The oscilloscope method is recommended for a show and tell demo.

https://www.edn.com/use-time-domain-reflectometry-tdr-for-low-cost-liquid-level-measurement-part-i/
https://www.edn.com/use-time-domain-reflectometry-tdr-for-low-cost-liquid-level-measurement-part-ii/
https://www.edn.com/use-time-domain...r-low-cost-liquid-level-measurement-part-iii/

 

It's possible to measure the delay (indirectly with a ADC measuring the linear change in voltage from a timed constant current source) with a PIC controller module called the CTMU if you want the display on the controller to show the data. You still will need the transmission line front-end logic to transmit and receive the pulse. The oscilloscope method is recommended for a show and tell demo.

https://www.edn.com/use-time-domain-reflectometry-tdr-for-low-cost-liquid-level-measurement-part-i/
https://www.edn.com/use-time-domain-reflectometry-tdr-for-low-cost-liquid-level-measurement-part-ii/
https://www.edn.com/use-time-domain...r-low-cost-liquid-level-measurement-part-iii/

I havae a spare esp32 from an old project, would that work? and do you have any links as to how I could go about making a pulse generator. I will be using EAGLE

 

I havae a spare esp32 from an old project, would that work? and do you have any links as to how I could go about making a pulse generator. I will be using EAGLE

Nope, the ESP32 won't work as it has no CMU module.

There are plenty of simple circuits online, do a search.

For a scope TDR demo you only need a 9v battery, a resistor and a tee to insert the DC ramp signal.

9V battery pulse.

 

I havae a spare esp32 from an old project, would that work? and do you have any links as to how I could go about making a pulse generator. I will be using EAGLE

What do you understand about the principles of tdr ?
Whats the block diagram of what you want to make ?
What sort of spec would you want from each of the blocks
As this is homework , we prefer to help by pointing and encouraging rather than say do xyz

 

There are plenty of simple circuits online, do a search.

Informative, but he's a poor speaker and said "and", "uh", and "ok" way too much. He seemed to know what he was talking about but, at the same time, wasn't very confident in what he was trying to say.

 

Informative, but he's a poor speaker and said "and", "uh", and "ok" way too much. He seemed to know what he was talking about but, at the same time, wasn't very confident in what he was trying to say.

I posted a very simple circuit in the video. #88: Cheap and simple TDR using an oscilloscope and 74AC14 Schmitt Trigger Inverter

but he still needs research (do a search) on other circuit implementations. It's homework so he shouldn't be spoon-feed a solution.

 

I posted a very simple circuit in the video.

I jumped around in that video. Did he ever give attribution to the original author? That circuit has been around for a couple decades.

Didn't watch any of the other videos.

 

Nope, the ESP32 won't work as it has no CMU module.

There are plenty of simple circuits online, do a search.

For a scope TDR demo you only need a 9v battery, a resistor and a tee to insert the DC ramp signal.

9V battery pulse.
View attachment 303845

thank ou this really helps, so I need to design and solder a TDR and a pulse generator.

 

I jumped around in that video. Did he ever give attribution to the original author? That circuit has been around for a couple decades.

Didn't watch any of the other videos.

That sounds like much ado about nothing.

 

That sounds like much ado about nothing.

It is if he passed it off as his idea. People who've done that to me got put on my sh*t list and the only way to get off of it was to die.

 

I saw that same circuit with a 74AC14 in an old issue of "QST" magazine. The oscilloscope used was a moderately high performance type. And the signal amplitudes were rather small. So I am not seeing how a slow processor and a slow A/D converter can make it work.

 

It is if he passed it off as his idea. People who've done that to me got put on my sh*t list and the only way to get off of it was to die.

His idea? That's a ridiculous response to the video IMO. It's a simple gate feed back and driver circuit anyone should be able to design in digital design 101.

 

I saw that same circuit with a 74AC14 in an old issue of "QST" magazine. The oscilloscope used was a moderately high performance type. And the signal amplitudes were rather small. So I am not seeing how a slow processor and a slow A/D converter can make it work.

Sure, it's a old circuit but accusing the video author of saying he 'invented it' is, IMO silly.

No, a slow processor and A/D converter won't work but the CTMU module combined with a slow processor and A/D converter will work.
https://forum.allaboutcircuits.com/threads/ctmu-for-time-measurement-calibration.66730/