Let There Be Light 

A Quest For Reliable Electrical Connectors 

When I bought my boat, it came equipped with a powerful and reliable hand-held spotlight. I consider a spotlight to be an essential piece of safety equipment when boating after dark. If I'm out at night, I keep mine plugged-in and at-hand in the cockpit.

Unfortunately, the spotlight had a flimsy power connector that was very unreliable. When you plugged the connector into the receptacle, the only thing that held it together was the friction of two small metal prongs. My spotlight has a coiled cord that was springy enough to accidentally unplug the connector. It was always an unpleasant surprise when the cord would spring back and everything would go dark. I resolved to replace the connector with something more reliable.

Other portable electronic devices use cigarette lighter plugs, but they also rely on a friction fit. Looking on the internet, I found a nice set of industrial-quality connectors manufactured by AMP, which I ordered online from Digi-Key (see the Resources section for details). The AMP connectors have a few advantages:

[Two-pin connector (friction fit).]   [Cigarette lighter connector (friction-fit).]   [Twist-lock plug and contact pins.]
The two types of connectors on the left are widely used but not very reliable. Consider replacing them with an industrial-quality twist-lock connector, shown on the right. It's a straightforward do-it-yourself project. Below, the twist-lock receptacle is covered when not in use. Once connected, the plug can't accidentally pull out.
[Closed twist-lock receptacle.]   [Twist-lock plug in receptacle.]

What You'll Need

All of the connector pieces are available separately so you can install new connectors or replace worn parts. Here's a breakdown of the parts you'll need. Consider getting extra parts as spares and to convert new equipment in the future. (A note on terminology: the plug goes on the end of the spotlight wire, the receptacle attaches to the boat.)

AMP CPC (Circular Plastic Connectors) Series 3, Shell Size 17
For each plug:ItemAMP Part NumberQuantity
Plug body206037-21
Socket contacts66740-81 per pin position
Cable grip207387-11
For each receptacle:ItemAMP Part NumberQuantity
Receptacle body206036-21
Pin contacts66261-11 per pin position
Cap207445-11

At last check, the approximate parts cost for a plug was $13.40 and for a receptacle $8.70. This might sound expensive, but the AMP connectors are good quality and work well. What's the cost of a cheap connector failing on a dark and stormy night?

Assembly Notes

Resources

AMP connectors are available online from Digi-Key or Allied Electronics.

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