Using a relay with a new Simrad autopilot

[skipmac]

Originally Posted by JOHNMARDALL

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

My original question has evolved into "can I use a smarter relay circuit to reduce the power draw of the clutch?" To me that seems like a good place to reduce the overall AP power usage.

[skipmac]

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.

So you sailed with Terrible Ted, the Mouth of the South. I loved it when he won the America's Cup and upset all the old school guys. Bet he was a real yuk to sail with.

I was living in Atlanta when TNT launched and used to watch all the old reruns, including Boston Blackie

[skipmac]

Quote:
Originally Posted by DeepFrz
Sure, that's what you need along with an ammeter.

Originally Posted by Reefmagnet

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

Yes, as I think about it, it's just a coil so won't care about low voltage, just total power in the circuit.

BUT, so far no time to play with it. Went out to the boat and like 99.9% of all boat projects, ran into glitches.

Simrad insists the compass should be at least one meter from any other unit in the system. This required moving the mounting location where the old Raymarine compass was located. The nearest and best was under a drawer in a nearby locker. Looked easy but nooooo.

Turned out there's no access between the locker and the rest of the boat, so I'm drilling access holes through five panels and bulkheads, none of course easy to reach. One panel is blind in between two other panels so had to come home to get my extra long bits to make a hole in that one. Then I get to fish a line through there which could be fun.

[LeaseOnLife]

Originally Posted by skipmac

My original question has evolved into "can I use a smarter relay circuit to reduce the power draw of the clutch?" To me that seems like a good place to reduce the overall AP power usage.

Not just for the AP, but I am looking to also reduce power to my propane solenoid. I haven't found an inexpensive source for an inline "pick and hold" PWM solenoid driver.

As for needed power, this Parker version reduces the Voltage to 30%:
http://www.hydrauliksysteme.com/WebR...llery/CE25.swf


Here are a couple of inline "pick and hold" PWM solenoid driver:

SDM 840 | Solenoid Electronics & Controls Catalog - Magnetic Sensor Systems at $101
https://apwelectromagnets.com/driver-circuits/ at $130
Blue Point Engineering Inc. - Sale Specials Sale at $75

A reduction to 30% of supply voltage seems common.

Dirk

[Boston Blackie]

Hello John

Wonderful to see Eagle still swimming! GREAT BONES.

[Boston Blackie]

Hi Skip
Amazing fun sailing with the caliber of folks ("county boys") Ted attracted.

[Boston Blackie]

Country boys

[skipmac]

Originally Posted by Boston Blackie

Country boys

Dontcha just love spell check.

[fallingeggs]

Skip, on the question of how much drawl the clutch will take, isn't it the clutch itself that determines the current drawl rather than the NAC output? In other words, the NAC will only push current (up to 3A) that the clutch requires?

Honest question as I have no idea and will be installing a NAC with a Jefa/Garmin (which I bet is similar to the Ray).

[fallingeggs]

Was looking at Jefa's website and the clutch draws 0.7 amps. I would have thought this is what will be used rather than the max output of 3 amps.

[skipmac]

Originally Posted by fallingeggs

Skip, on the question of how much drawl the clutch will take, isn't it the clutch itself that determines the current drawl rather than the NAC output? In other words, the NAC will only push current (up to 3A) that the clutch requires?

Honest question as I have no idea and will be installing a NAC with a Jefa/Garmin (which I bet is similar to the Ray).

This is correct. The clutch will draw as much power as it needs regardless of the max supply available. So even if the AP computer could put out 10-20 amps the clutch would still draw the same.

I looked at the Jefa pilots. Their website looks really good but anyone can make a good website. I have read that Jefa is the OEM to some of the big AP companies but haven't been able to find much information on cruisers' experience with the Jefa units. What made you decide to go with the Jefa drive? Also, which one?

[skipmac]

Originally Posted by fallingeggs

Was looking at Jefa's website and the clutch draws 0.7 amps. I would have thought this is what will be used rather than the max output of 3 amps.

One thing of great interest to me is the claims by Jefa of lower power draw by there drives. Have you looked into this in any detail?

[DeepFrz]

This is correct. The clutch will draw as much power as it needs regardless of the max supply available. So even if the AP computer could put out 10-20 amps the clutch would still draw the same.

Actually the current through the clutch coil will vary with the voltage supply. If the supply voltage is constant the current will be essentially constant varying only with the change of resistance of the coil as it's temperature changes. Ohm's law still rules in this situation.

[skipmac]

Originally Posted by DeepFrz

Actually the current through the clutch coil will vary with the voltage supply. If the supply voltage is constant the current will be essentially constant varying only with the change of resistance of the coil as it's temperature changes. Ohm's law still rules in this situation.

Of course correct and if one wants to get really technical we can look at the reverse EMF generated when the first current passes through the coil, temp compensation, etc. But keeping it simple (simplied?) for the question, the current in the clutch is overwhelmingly determined by the clutch solenoid and assuming the clutch draw is well within the supply capacity, not determined at all by the max potential output of the AP computer.

[fallingeggs]

Originally Posted by skipmac

One thing of great interest to me is the claims by Jefa of lower power draw by there drives. Have you looked into this in any detail?

Garmin's Class A drives are Jefa's LD100s, which is what I am going for. Garmin includes a built in rudder sensor that probably only works with a Garmin computer. Will probably buy a Garmin branded one as they are easier to find in the US. Will use the B&G rudder sensor.

No detail as to whether they are really lower power. Practically impossible as you will need someone to do A-B testing with it and the Ray drive on the same boat and sailing conditions. Looking at the graphs suggests they are on to something, but that is just a few pictures.

I figure they can't be worse than the Ray's. I don't mind being another date point. I have to stop researching and buy something at some point. Finally, I still reserve the right to change my mind at any point.