How to prevent wiring mistakes?

[Jez09]

Consider the simple scenario:

You have two connections on a board that you are trying to wire to another two points.

How can you ensure the wires are connected correctly or guarranteed the wires are not crossed?

The intuitive simple method I can think of is to have 2 LEDs for each wire, and making sure that the LED light up in sequencial order. Namely, you connect the first wire, the first LED should light up, not the second one. If the 2nd LED lights up, oops, you mis-wired.

But this requires trust in the person doing the wiring. What if the person was sleepy that day and overlooked?

Is there another way I am missing, that can guarrantted the wires are connected correctly?
Any ideas?

 

[negitron]

In the industry, we either label wire ends with labels, use color-coded wires or run one wire at a time. Adding complexity adds cost.

 

[berkeman]

Consider the simple scenario:

You have two connections on a board that you are trying to wire to another two points.

How can you ensure the wires are connected correctly or guarranteed the wires are not crossed?

The intuitive simple method I can think of is to have 2 LEDs for each wire, and making sure that the LED light up in sequencial order. Namely, you connect the first wire, the first LED should light up, not the second one. If the 2nd LED lights up, oops, you mis-wired.

But this requires trust in the person doing the wiring. What if the person was sleepy that day and overlooked?

Is there another way I am missing, that can guarrantted the wires are connected correctly?
Any ideas?

Another strategy is to use keyed connectors and a cable. As long as the keyed connectors are loaded in the PCB correctly, and as long as the cable is made correctly, the connectivity is ensured. To ensure that the cable is wired correctly, you can use a cable tester in production (most cable making houses have cable testers as part of their manufacturing flow).

 

[Jez09]

Let's say cost is not a concern here (to a certain point obviously) and that color coded wires and labels are not enough to prevent operators from making mistakes.

Are there any tricks or methods (electrical, mechanical, software?), to guarranteed the wires are connected correctly 100% or 99.99% of the time.

Thanks,

 

[negitron]

Another strategy is to use keyed connectors and a cable. As long as the keyed connectors are loaded in the PCB correctly, and as long as the cable is made correctly, the connectivity is ensured.

those are a lot of IFs which, unfortunately, don't always fall where they're suppoed to. We have a board production company we buy our PCBs from and you would not believe how often we find wire-to-board connectors installed backwards (and not just connectors, either: diodes, polarized caps, LEDs). I don't know 1) how this place stays in business and 2) why we keep buying boards from them; although I suspect the anser to both is, "they're cheap."

 

[Integral]

The bottom line is if it aint wired right it doesn't work. There is no point in adding more circuitry to attempt to check wiring, when there is no guarantee that the added circuitry will be wired correctly.

If a circuit performs as designed then it is wired correctly, if it does not work then you must troubleshoot the circuit to find the problem. Once it is working you do not have to change the wiring.

Wiring of major tools is (best) done by well trained technicians, who once the wiring is done check functionality. There is never a way to guarantee 100% correct connections in manually wired devices, this is why testing is an essential part of the assembly.

 

[negitron]

Wiring of major tools is (best) done by well trained technicians, who once the wiring is done check functionality. There is never a way to guarantee 100% correct connections in manually wired devices, this is why testing is an essential part of the assembly.

Yep. Good thing, too--it keeps me employed!

 

[turbo]

I once built a clone of a Fender Tweed Deluxe tube amp (5E3), using all yellow-jacketed wire. It worked perfectly on the first fire-up, but that's a LOT of wiring to keep track of. In retrospect, it might have been a good idea to color-code all ground leads with green, B+ rail leads to the tubes with another color, etc, etc, just to protect the sanity of anybody who might have to work on that amp in the future.

Never wire when you're tired, and check and re-check before plugging it into line current.

 

[Jez09]

Let me rephrase my question.

Is it possible to add some sort of circuitry, or perhaps some mechanical device, or use some software or microcontroller, so that once the work is done and verified, it can prevent miswiring going forward?

Something to alert the person that he is attempting to connect wire1 to wire2 on the spot.

Let's say we have person A will be mass producing a board, and person B is to set something up to fool proof person A from screwing up.

Thanks,

 

[dlgoff]

Yep. Good thing, too--it keeps me employed!

I bet you've done wire-wrapping. Talk about keeping track of wires. One really needs a check list for the point to point wiring.

See if this doesn't bring back memories: http://en.wikipedia.org/wiki/Wire_wrap"

 

[negitron]

You betcha. But, I can't imagine the level of dedication and patience required to build this. Rat's nest doesn't even begin to cover that nightmare.

 

[turbo]

You betcha. But, I can't imagine the level of dedication and patience required to build this. Rat's nest doesn't even begin to cover that nightmare.

Argh! That is beyond scary! I don't mind building something on tag-board or project-board, but that mess is horrid. It's hard to believe that such a mess had enough volume-sales to justify the prototyping and programming.

 

[Redbelly98]

Let me rephrase my question.

Is it possible to add some sort of circuitry, or perhaps some mechanical device, or use some software or microcontroller, so that once the work is done and verified, it can prevent miswiring going forward?

Something to alert the person that he is attempting to connect wire1 to wire2 on the spot.

Let's say we have person A will be mass producing a board, and person B is to set something up to fool proof person A from screwing up.

Thanks,

As berkeman said earlier, using keyed connectors would be a good idea.

Alternatively, design diagnostic tests that would not cause components to blow in the event of miswiring. So that you can catch the error and rewire without having to replace chips or other components. Simple continuity checks may suffice.

If you want more specific answers, I think you'll have to give more details yourself first. What is the problem, presumably at your workplace, that miswiring is happening frequently? Is it a problem with one particular worker, or with several workers?