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Old 13-05-2013, 17:30   #1
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Switch nomenclature

I'm exploring the idea of replacing my Lewmar bow thruster control panel with a rotary knob/switch.

I need some help from from electrical gurus on how to describe it (as well as where to find it).

This is the current switch (on the left):

I'd like a rotary knob that is spring loaded to center (OFF) and will turn say 45* to the right or left for ON-R or ON-L. Plus will need some push ON, Push OFF button to arm the rotary switch.

Is this what I'm looking for? Rotoswitch Rotary Switch 2 Position M/On-Off-On - Sierra MP78750 - iboats

If not, can someone give the "technical" terms that describe a switch that does what I'm trying to do.

Since the boat "twists" when the BT is used, I think a switch that twists would be more intuitive...the buttons are subject to "reverse sensing" for the pilots on the forum, whereas a knob visually depicts what you want the bow (or stern) to do.

I was teaching my wife how to back into the slip with a strong crosswind this weekend...
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Old 13-05-2013, 18:07   #2
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Re: Switch nomenclature

Why not just reverse the left/right leads. The type of plastc connectors you have on these switches have pins that are easily removed. They actually make a tool for it but you can easily do it with a couple of jewlers flat bladed screw drivers. If you look down one of the holes you can see a tab on either side of the pin that locks the pin in the plastic holder. Depress these with the crew drivers and a gentle pull on the wire takes the pin out. Reverse the left and right hot wires and you should get the reaction you want. The tabs will lock the pins back in place when you reinsert them. If you press to hard with the screw drivers the pins may not spring back out by themselves and you will need to gently bend them back into position. You will have to determine which wires get the juice when you throw the switch but that can be easily done with a volt-ohm-meter. That should be a lot simpler than trying to reengineer the whole system.
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Old 13-05-2013, 18:09   #3
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Re: Switch nomenclature

The rotary switch you show is a "SPDT" (Single Pole Double Throw) switch, and has three terminals: Common, Normally Open A, and Normally Open B. The Lewmar switches in your photo apparently have four terminals, and looking at the Lewmar catalog, these might have built-in protection circuitry and other complications. I can't tell what type of switch you will need, and to be honest, if you don't know either you should probably get some expert local help.

Neither of these switches will be directly feeding the thruster (electric?), but are probably driving a relay box. Can't you use the Lewmar Joystick version?
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Old 13-05-2013, 18:47   #4
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Re: Switch nomenclature

Ha. I knew when I posted this, I'd be misunderstood...both in my description and in my purpose.

CaptBill, I'm not trying to make the switch backwards. If you push the Green button, the bow moves to Starboard and the stern moves to port. With a rotary switch (esp if knob is shaped like a boat) that movement is "visualized" if the knob is rotated to the right. The visualization works whether you are facing backwards while driving in reverse or if you are moving forward. With the current button method, you have to do some mental gyration if you are facing backwards and reaching behind you to push a button...

Paul,
I figured that the 4 terminals in the current switch had to do with the additional Power ON/OFF function...I also assume they went to relays. I don't know about additional circuitry in the switch other than turning on the panel lights. I haven't traced or metered out any of the wiring yet, but it doesn't seem like it'll be rocket surgery.

So the technical description is momentary SPDT rotary knob?
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Old 13-05-2013, 19:08   #5
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Re: Switch nomenclature

Quote:
Originally Posted by 67Therapy View Post
I'm exploring the idea of replacing my Lewmar bow thruster control panel with a rotary knob/switch.

I need some help from from electrical gurus on how to describe it (as well as where to find it).

This is the current switch (on the left):

I'd like a rotary knob that is spring loaded to center (OFF) and will turn say 45* to the right or left for ON-R or ON-L. Plus will need some push ON, Push OFF button to arm the rotary switch.

Is this what I'm looking for? Rotoswitch Rotary Switch 2 Position M/On-Off-On - Sierra MP78750 - iboats

If not, can someone give the "technical" terms that describe a switch that does what I'm trying to do.

Since the boat "twists" when the BT is used, I think a switch that twists would be more intuitive...the buttons are subject to "reverse sensing" for the pilots on the forum, whereas a knob visually depicts what you want the bow (or stern) to do.

I was teaching my wife how to back into the slip with a strong crosswind this weekend...
I would suggest learning to use the stock switches. The manufacturer put a lot of thought into their design. If I were to replace my switches (push buttons), I would go with the joystick pictured.

Now to partially answer your question: A "push on/push off" switch is a poor choice for "arming" the other switch, whichever style you have. A "push on/push off" switch gives no visual indication of whether the circuit is made or not. Without adding an indicator light, you could not walk to the helm and see if the thruster is ready to use or not. A toggle switch, rocker switch, or even a rotary switch would be a much better choice.

If you really want to replace your existing switch, you have to identify exactly what it does. Having four wires, it is not just a single pole, double throw, spring return center off switch. Unless one of the wires is a dummy or unless it's a neutral for a lighted switch.

Since a replacement switch won't come with that wiring harness you will have to understand exactly what the switch does and which terminal connects to which wire on the harness.
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Old 13-05-2013, 19:50   #6
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Re: Switch nomenclature

I'm after a better mousetrap...I am able to use the current switch just fine...

The Lewmar pushbutton ON/OFF switch enables the PORT/STARBOARD pushbuttons, lights up the PORT/STARBOARD pushbuttons, and also sets a timer (15 mins or so) before powering the switch down.

From the Lewmar manual:
Loom:
Red: +VE
Blue: Thrust port switch
Grey: Thrust starboard switch
Black: -VE

A pushbutton with light would work fine in my mousetrap. The lighted pushbutton would put power to the momentary rotary knob...I guess via a relay. I hadn't really intended on designing the circuit tonight in this thread...

All I really wanted to know is how to describe a knob that works the way I described to see if I could find something that would work...otherwise the whole idea is moot.
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Old 13-05-2013, 20:54   #7
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Re: Switch nomenclature

Rotary single-pole double throw, center-off, spring return. Might be tough to get just the throw angle you want.
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Old 13-05-2013, 21:21   #8
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Re: Switch nomenclature

Thanks for the nomenclature...I'm back to googling!
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