Creating a Custom Cable: 7-Pin Amphenol Connector and Unique Electrode Input

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Discussion Overview

The discussion revolves around the construction of a custom cable featuring a 7-pin Amphenol connector and a unique electrode input. Participants explore the feasibility of sourcing components, the appropriate wiring techniques, and considerations for signal integrity in the context of biomedical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster (OP) seeks information on sourcing a specific white electrode input socket and inquires about the feasibility of constructing a cable instead of purchasing a $200 pre-made one.
  • Some participants suggest using twisted wires similar to those in Ethernet cables and propose shielding the wires within a grounded screen to minimize noise.
  • There is a discussion about wire size, with one participant noting that it depends on the unspecified signal amps and voltage, which affects insulation requirements.
  • Concerns are raised about how cable length might introduce noise, with one participant indicating that a screened twisted pair should be reasonably quiet at 1 kHz.
  • One participant calculates the wavelength of a 1 kHz signal and suggests that impedance mismatches should not be problematic due to the short length of the cable compared to the wavelength.
  • The OP mentions the use of 1.5mm touchproof sockets and specifies that the voltage relates to biopotentials of human skin surface, questioning if Ethernet cable is suitable for this application.
  • Another participant questions the high cost of the pre-made cable, prompting a discussion about its features and intended use.

Areas of Agreement / Disagreement

Participants express varying opinions on the best practices for cable construction, including wire type and shielding methods. There is no consensus on the sourcing of the electrode input or the specific requirements for the cable, leaving the discussion unresolved.

Contextual Notes

Participants have not specified the exact electrical characteristics required for the cable, such as signal amplitude or environmental noise levels, which could influence their recommendations. The discussion also lacks detailed specifications for the electrode input socket.

Ephant
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electrode input cable.jpg


This cable costs $200 so I want to build one. I know where to get the round silver plug at right which is a 7 pin Amphenol and I know the pin designations inside.

I'd like to know if the left white electrode input socket can be found anywhere or it can only be made special at factory. Have you seen anything like it being sold anywhere?

The red (+) and black (-) input is differential with a ground/reference at middle. Should I use twisted wires like used in ethernet cable as the cable? What is the size of wire I should use. How many feet before it can cause enough noises?

I plan to use up to 1000 Hz signal. If the wire and plugs at either end is not matched. Would the impedance mismatched attenuate or cause noises in the signal?

Thanks!
 
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Ephant said:
Have you seen anything like it being sold anywhere?
What are the physical dimensions of the shell and the electrodes?
Ephant said:
The red (+) and black (-) input is differential with a ground/reference at middle. Should I use twisted wires like used in ethernet cable as the cable?
Twist the (+) and (-) wires, and shield them inside the grounded screen.
Ephant said:
What is the size of wire I should use.
That depends on the unspecified signal amps, the voltage determines the insulation.
The wire should fit in the shell, and terminate sensibly at the electrodes.
Ephant said:
How many feet before it can cause enough noises?
Many. At 1 kHz, a screened twisted pair will be reasonably quiet. How much noise do you need to avoid, and in what environment?
Ephant said:
I plan to use up to 1000 Hz signal. If the wire and plugs at either end is not matched. Would the impedance mismatched attenuate or cause noises in the signal?
The wavelength of a 1 kHz signal would be 3e8/1e3 = 3e5 = 300 km. The cable is very much shorter than that, so there should be no problems at 1 kHz.
Only the total lump capacitance of the cable would be important.
 
It's 1.5mm Touchproof sockets. Voltage is biopotentials of human skin surface. So I can just use ethernet cable?
 
Why do you suppose it costs $200? What-all does it do? What does it plug into?
 
Thread is closed for Moderation...
 
Because this appears to be related to the OP's DIY Biomedical experimentation, the thread will remain closed.
 

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