Using a relay with a new Simrad autopilot

[DeepFrz]

Wouldn't be too difficult to rig a variable voltage supply but that wouldn't be the ideal

Sure, that's what you need along with an ammeter.

[Reefmagnet]

As a wild guess I'd say about 1/2 to 1/3 the nominal operating power. The kicker is you'd need an efficient power regulator to do this otherwise you'd be essentially dissipating much of the "saved" energy into the regulating circuit. I'd be thinking pwm or fet control.

[Reefmagnet]

Originally Posted by DeepFrz

Sure, that's what you need along with an ammeter.

Yep it's the power that matters. What combination of amps and volts to achieve that power are inconsequential.

[AnsleyS]

I would check the amperage used by the drive clutch vs the allowed for the pilot circuit. That is why they want you to use a relay. If you are under the allowed amperage by a long shot then forget the relay but if you are close then put in in.

[Paul L]

Originally Posted by AnsleyS

I would check the amperage used by the drive clutch vs the allowed for the pilot circuit. That is why they want you to use a relay. If you are under the allowed amperage by a long shot then forget the relay but if you are close then put in in.

Exactly, the clutch power required by the Ray linear drive is low enough to be powered by almost any AP controller.

[AnsleyS]

I always want to see the numbers and make sure that it is well under the max

[davefrediam]

When I installed a Raymarine SPX30 autopilot (drive via a type 2 hydraulic pump) in my yacht which had no previous autopilot I didn't originally bother with a relay between the spx clutch supply and hydraulic system solenoid as I thought that at 10 watts draw it would be fine. However my yacht has two steering positions, one in the pilot house (hydraulic) and one in the cockpit (mechanical). The pilot house steering position is activated via the same solenoid (as the autopilot clutch activates) and there is a switch that must be flicked at this position to supply power to the solenoid for the inside steering position to work. Incredibly enough what I found was when I switched on the inside steering position with the autopilot switched off the autopilot would power up despite being isolated at the switch board! So if you supply 12v to the clutch electrical connectors on a Raymarine spx30 it will power up the whole autopilot via them and whats more the autopilot was the 24v version and you could actually hear that the pump was running at half speed if you engaged the autopilot being run off 12v instead of 24v!
So I ended up having to install a relay between the spx clutch supply and solenoid to isolate it.

[JOHNMARDALL]

Originally Posted by skipmac

Thanks John. I do agree that adding a relay is a simple, low cost solution. My original question was just what kind of relay would be the best to use for this application but the discussion morphed into related issues.

Since I do have an EE degree and am a curious type I like to ask and understand why instead of blindly following the instructions. I have to say more than once asking why has revealed bad information in manuals or helped me find a better solution. Not saying the recommendation or manual from Simrad is bad or wrong, in fact quite the contrary, but I still like to understand the whys and wherefores.

So my question now, the Simrad computer has a 3 amp engage output which is used to activate the solenoid operated valves on the Simrad hydraulic drives. It is the exact same setup on both brands, the engage/clutch output from the AP computer Raymarine or Simrad goes to a solenoid on the drive, Simrad or Raymarine. Why would Simrad solenoids be any different, have any lower inrush current than the solenoid used by Raymarine? Note this output is connected only to and isolated from the power that drives the AP motor so the spikes that might result from a motor kicking in/out don't contribute.

Hello again Skip,

Your post has stirred up a hornet's nest. What you say is logically correct, and I agree that occasionally one can find manufacturer's information that is questionable, but with an expensive piece of electronic equipment like an autopilot, I just would not take a chance on not following the manufacturer's recommendation. In my work I've encountered quite a few equipment failures where there was a variable or operating condition that had kicked in and damaged equipment that had no reported incidents of a similar malfunction. Both Simrad and Raymarine are excellent companies with great products, and I wouldn't expect any intrinsic problems with any of their equipment, but my guess is that Simrad is making its relay recommendation based on real world experiences - it's surprising what can happen when insulation chafes through, connections come loose, corrosion causes clutches to jamb and all the other thousand shocks that boats are heir to.

I think we've beaten this subject to a pulp, so good luck with whatever you decide to do.

All the best
John M

[tanglewood]

Which Simrad/B&G AP computer are you using? Is it one of the NAC 1,2,3 models, or an older AC12/24?

If it's an AC12/24, I know of a number of instances where people have had issues driving loads from the Enable output. There is no published spec for the output, and phone calls to simrad have resulted in mixed answers, but suggest a load capacity of an amp or less. So if you are using an AC12/24, I would definitely use a relay.

It sounds like the NAC 1,2,3 have a published spec for the Enable output? If no, then never mind this post.

[Boston Blackie]

Ahoy Scipmac,
I Have used these DC SSR to run our PLC plastic membrane welder for decades. No failures. The 120&240VAC SSRs running the high current heaters fail occasionally.

I was one of 2 Bills on American Eagle with Turner offshore so I became Boston Bill which he morphed to Boston Blackie, which he was retiring on his new Atlanta TV Station.

[Boston Blackie]

Re-airing.

[Boston Blackie]

Sorry for typo Skipmac,
Our J42 was built with complete dual Robertson Type 2 and Type 3 pilots. Dual computers and angle sensors and pumps and cylinders. The type 3 was massively too big and slow for the 42s finger touch steering. Not used. The computers and peripherals started heading South before the rest of the rig. I replaced the Type 2 computer with a high end Raymarine Computer with the stinger missle guidance sensors. The I removed the Type 3 Hydraulics and remounted the Type 2 pump with snowplow quick connects so it can be unplugged for service. The tiller arm position of the Type 3 pump had the exact 8" radius Yeves Gelinas wanted for the control line bocks of the Jeand du Sud Cap Horn vane. Cap steers to weather flawlessly.

[JOHNMARDALL]

Originally Posted by Boston Blackie

Ahoy Scipmac,
I Have used these DC SSR to run our PLC plastic membrane welder for decades. No failures. The 120&240VAC SSRs running the high current heaters fail occasionally.

I was one of 2 Bills on American Eagle with Turner offshore so I became Boston Bill which he morphed to Boston Blackie, which he was retiring on his new Atlanta TV Station.

Hello Bill,

It's a small world - we supplied a new engine and exhaust system for American Eagle a few years ago

John Mardall
Vetus Maxwell Group

[donradcliffe]

I'm pretty sure my Simrad AP had a solenoid over current detection and alarm circuit. I'd plug it in and try it for a while before I went nuts.

[skipmac]

Originally Posted by tanglewood

Which Simrad/B&G AP computer are you using? Is it one of the NAC 1,2,3 models, or an older AC12/24?

If it's an AC12/24, I know of a number of instances where people have had issues driving loads from the Enable output. There is no published spec for the output, and phone calls to simrad have resulted in mixed answers, but suggest a load capacity of an amp or less. So if you are using an AC12/24, I would definitely use a relay.

It sounds like the NAC 1,2,3 have a published spec for the Enable output? If no, then never mind this post.

I have the NAC-3 computer that specs 3 amps max output on the enable circuit. Manual doesn't say if that is 3 amps continuous or peak but even if it's peak I think that is way more than the clutch draws. One of the Raymarine computers that is spec'd to use the same drive I have only shows 2 amps in the enable circuit.