Can Raymarine ACU 100 Power Backbone?

[RogerJolly]

Am finding below bits of the Raymarine documentation confusing.

If the ACU 100 can’t power the ‘backbone’, why is it connected to it with 12V cables?

Any insight much appreciated. This is really tweaking my OCD!

 

[KeelsonGraham]

From memory, I think it does, via a switchable option. Just make sure you don’t have two separate power supplies to the backbone,

 

[PaulRainbow]

Am finding below bits of the Raymarine documentation confusing.

If the ACU 100 can’t power the ‘backbone’, why is it connected to it with 12V cables?

Any insight much appreciated. This is really tweaking my OCD!

View attachment 157474

Not sure why you are confused, the image you posted clearly states that the ACU-100 and ACU150 do not provide power to the backbone.

 

[KompetentKrew]

If the ACU 100 can’t power the ‘backbone’, why is it connected to it with 12V cables?

I would guess it's to provide a voltage level against which voltages on the data wires are compared.

When I got my AIS I initially connected it to the plotter without powering the bus, thinking the 12v on the bus would be unnecessary seeing as both devices had their own supply. Wondering why it didn't work I added 12v to the bus and - like magic! - the plotter started to see AIS data.

 

[RogerJolly]

Good info thanks people. From the documentation, it's only the higher spec (ACU 200 up) units that have the switch to power the network.

What with PaulR's post tailing off a bit, got some additional speculation:

* Standard bare ends network cable includes power wires, so need somewhere to put these. Terminals don't connect anywhere inside the ACU 100.

* Or the ACU 100 can draw power from the network, but limited and not as much as from dedicated power connection.

Be good to know as I'm trying to work out the inherited system on my boat.

Cheers

 

[Sandy]

If the ACU 100 can’t power the ‘backbone’, why is it connected to it with 12V cables?

It is traditional to power DC devices from the battery.

Google informs me that the ACU 100 unit is a 'is a key component in Evolution autopilot systems' and does not generate any power.

 

[PaulRainbow]

Good info thanks people. From the documentation, it's only the higher spec (ACU 200 up) units that have the switch to power the network.

What with PaulR's post tailing off a bit, got some additional speculation:

* Standard bare ends network cable includes power wires, so need somewhere to put these. Terminals don't connect anywhere inside the ACU 100.

* Or the ACU 100 can draw power from the network, but limited and not as much as from dedicated power connection.

Be good to know as I'm trying to work out the inherited system on my boat.

Cheers

Sorry Roger, don't know why my last post was cut short, i've edited it.

Unlike earlier autopilot controllers, the ACU series are just controlling the clutch and drive motors. So, it has to have relatively sizeable wiring to it and onwards to the drive.

The Seatalk connection is simply there to activate the clutch and drive circuitry.

The EV-1 sensor core handles everything else, which was previously processed by the early type ECUs, with heading data from a fluxgate compass.

The ACU100/150 do not output power to the Seatalk backbone. Logic suggests that the Seatalk power connections are therefore supplying power from the ST network, to the control circuitry within the ACU (although i've never taken one apart to verify this).

Personally, i've never liked the idea of powering the Seatalk network from the autopilot, even on models where that functionality was/is present. Doing so means that without the autopilot powered up and functioning the Seatalk network doesn't work. I would rather have a switch for the AP and a separate switched supply for the network. That way, for example, you could sit at anchor and keep an eye on the depth with the minimal amount of power usage.

Roger, if you're trying to see how the network is powered, look for a black and red striped cable plugged into the network.

 

[RogerJolly]

Thanks Paul.

Inherited such a system – came installed in the boat.

Will need to start working on it soon. Hard enough tracing out unfamiliar system wiring, so any pre-knowledge got to be good!