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ContinuousWave: Small Boat Electrical
Power for Chart Plotter
|Author||Topic: Power for Chart Plotter|
posted 07-07-2014 01:43 AM ET (US)
I have my new Garmin 741 installed. Its power is tied to the main switchboard and runs off the ACC accessory switch. Upon switching the switch unit starts, and off we go--in that we don't seem to use the unit's ON-OFF switch. Anyone see a problem with that? I feel that turning ON-OFF a better scenario than simply cutting and restoring power
posted 07-07-2014 06:47 AM ET (US)
No problem either way. Personal choice when wiring.
posted 07-07-2014 09:15 AM ET (US)
If a device has an ON-OFF switch, and by that I mean a toggle switch or some other two-state switch which is moved mechanically from ON to OFF and the power just shuts off instantly, then I don't see much difference in operating the device with that power switch left in the ON position and installing another switch upstream, in the power wiring, that does the same thing.
I am not familiar the Garmin chart plotter 741, and I don't know if it has such an ON-OFF switch. If it does, and you can hit the switch and the 741 just shuts off instantaneously, I would be surprised. Most modern chart plotters are really rather complicated computer systems, and they usually have a software function that is invoked to suspend their operation and then shut off the power. With a device like that I think it would be a risk to just constantly shut off the power with an external switch.
A good source for advice on this is probably the installation instructions from GARMIN and the operating instructions, too. I'd read them over thoroughly to see if they suggest anything about proper shutdown procedure.
posted 07-07-2014 12:28 PM ET (US)
Great info guys & thanks, I sent an email request to Garmin's tech people.
posted 07-07-2014 07:27 PM ET (US)
The only thing that occurred to me is that if you are fishing and turn your ignition switch off each time you move your chart plotter will have to cycle on when you start your engine to move. If you drift fish it is nice to keep your chart plotter on to keep track of your position and the depths under your boat and perhaps to see a fish in the water column once in a while.
I wonder if it is more likely the chart plotter will feel a voltage drop/surge when starting when powered from the ignition switch than when powered from the battery bank.
My habit is to turn my ignition switch off when the engine is stopped. I suppose I could become used to only turning the switch to acc to shut off the engine.
posted 07-07-2014 07:39 PM ET (US)
I'm with you Butch, I want it direct wired, not sure if it runs with the engine off. We troll with the main engine so that settles most of the time but often bottom fish jigging & drifting along. Good point, I'll have to look but nonetheless, I don't like voltage spikes & just cutting power. When I hear back from Garmin I'll post something
posted 07-07-2014 10:52 PM ET (US)
Both my Raymarine chartplotters (C80/C70) require that you press and hold the power button to shut the unit down properly. It takes about 4 seconds and displays a countdown while shutting down.
You wouldn't just yank the power cord of your PC out of the wall, would you?
Use the power button on the unit.
posted 07-08-2014 08:07 AM ET (US)
Dave's correct, today's chartplotter/sonars are really computers with transducers and GPS receivers attached to them. They have preprogramed orderly shutdown sequences that they do through to preserve memory stuff and settings. Let them work as they were designed, a sudden power failure is not a good thing.
posted 07-08-2014 08:24 AM ET (US)
I am somewhat surprised that you have to contact Garmin technical support to find out how to shut off the Garmin chart plotter. Don't they describe that in the operating guide?
posted 07-08-2014 08:53 AM ET (US)
In today's new world of multiple-screen systems, many chart plotters and MFDs have the capability of acting as a "slave" unit, whereby one MFD or chart plotter can be turned on or off by powering a separate MFD or chart plotter on or off. I suspect that's what is going on here. Somebody has set up the Garmin 741 as a "slave" unit so that whenever it gets power it turns on, and whenever the power is cut the unit shuts down. If this is the case, I don't believe shutting the unit down by cutting the power will be harmful.
posted 07-08-2014 09:02 AM ET (US)
The owners manual for the Garmin 741 includes the following passage:
This would seem to indicate that the unit may take up to two minutes to completely shut down after the power has been cut.
posted 07-08-2014 08:18 PM ET (US)
Somewhat akin to what Kevin is describing, there is an arrangement of power wiring that provides for one device to control a second device through an extra conductor, often called the wakeup conductor. The power wiring is provide on three conductors, often color coded like this:
RED is the positive power conductor;
BLACK is the negative power conductor; and
YELLOW is the wakeup conductor.
The RED and BLACK are wired to the power distribution bus. There is no controlling power switch in the RED-BLACK circuit. The YELLOW is wired with several options:
--if another device from the same manufacturer is intended to be the master power controlling device, the YELLOW wire is connected from the first device to the master device; or,
--the YELLOW wire can be run to a switch. The switch is connected to 12-Volt (positive) power, and when the switch is thrown, the first device will wakeup and power on. If the switch is shut off, the first device powers down. I think you can expand this to more than one device connected via the YELLOW, if the devices are all compatible with this method, that is, all from the same manufacturer.
With the second option, a master ON switch wiring, you can turn a device on and off without having to hit its power button.
This method only works with certain NAVICO devices, notably the ones with the SIMRAD brand. They can be set to either generate a wakeup signal on the YELLOW lead, that is, act as the master device, or to listen for a wakeup signal on the YELLOW lead, that is, act as a slaved device. With this method I think you could set up several SIMRAD devices (all as slaved devices with regard to the YELLOW wire) to all power on with the throw of one switch, which would put power on the YELLOW lead of all the devices' power cable. I do not think you can do this with Lowrance HDS G1 devices. You may be able to do it with some Lowrance HDS TOUCH devices. I think you can do it with the new SIMRAD evo2 devices. I don't know if Garmin uses that third wire, the wakeup conductor. I think Kevin is saying you can set the Garmin to always power on when there is power on its RED-BLACK power circuit.
posted 07-09-2014 09:39 AM ET (US)
After doing some more reading on the web about the HDS and YELLOW wakeup wire, and also contacting Lowrance support, it seems that the HDS Gen-1 chart plotters cannot have their ON-OFF function controlled by the YELLOW wakeup wire. The HDS Gen-1 chart plotters always operate as the master device. They can wakeup accessories, but they themselves don't respond to a signal on the YELLOW wakeup wire.
There are also some reports that even with the new SIMRAD evo2 chart plotters, which are said to be able to be switched in their mode of operation from being a master device to a slaved device in terms of response to the YELLOW wakeup wire, it appears that there are some problems in configurations with more than one chart plotter connected to the YELLOW wakeup wire bus.
The simplest approach to provide the ON-OFF function for a chart plotter is to just use its front panel power button. And, as everyone has noted, there is a very strong probability that just disconnecting the power to the chart plotter with an external switch is not a good method for shutting down the chart plotter. While such a method might be tolerated, I believe there is greater risk for harm to the computer file system inside the chart plotter by repeatedly just interrupting the power to the device.
posted 07-10-2014 09:00 AM ET (US)
Yes the power off button is simply an input to the unit's computer, like any other button on the unit. If it is triggered, it tells the computer to initiate a shutdown sequence.
Manufacturers have to design the unit with a certain amount of tolerance to immediate power cutoffs, because those things happen. But as has been mentioned, they can't cover every possible internal state, and there is certainly exposure to damage.
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