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Old 30-06-2016, 00:35   #16
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Re: Autopilot wiring question

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Originally Posted by Snowpetrel View Post

Stu, I am more and more convinced the problem is exactly this. Bigger wires and a shorter run directly to the battery. Hopefully this will also cure the HF interference issue as well.
If the HF interference has increased it might be a clue to where the problem is.

Sparking at the commutator in the DC motor can cause radio interference.

And,

If the voltage across the rotor coils is low due to poor commutating the motor might be pulling excessive current hence greater voltage drop across the power cables.

I recently skimmed a commutator on a Simrad hydraulic drive autopilot for a friend and it was in very poor condition so they do wear.
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Old 30-06-2016, 01:06   #17
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Re: Autopilot wiring question

Ben, it depends on the pump. For example, the Simrad RPU 160 can draw up to 47 amps (at stall), but of course it virtually never gets that high. Cables, and a circuit breaker, must be sized to suit that max load. A thermal circuit breaker can be used so that, for example, it will allow stall for 5 secs (or whatever) then flip the circuit breaker if the load is still there. Of course short or higher load should never happen, and would overload the circuit breaker more quickly.
Soft start - it should be smooth now - the AP software should start the motor slowly for minor corrections, and faster for major ones. If it is not doing that, the motor could have an issue (Has it had brushes/bearings replaced etc)
The H bridge I have used is from Robot Power Products - Simple-H & HV - H-bridge and you can read on that page about others who have solved the issue with one of these.
Cheers
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Old 30-06-2016, 05:13   #18
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Re: Autopilot wiring question

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If the HF interference has increased it might be a clue to where the problem is.

Sparking at the commutator in the DC motor can cause radio interference.

And,

If the voltage across the rotor coils is low due to poor commutating the motor might be pulling excessive current hence greater voltage drop across the power cables.

I recently skimmed a commutator on a Simrad hydraulic drive autopilot for a friend and it was in very poor condition so they do wear.
Very interesting Raymond. The unit hasn't seen that much use, maybe a few thousand miles or so, so hopefully it is not to bad, but then you never know. Might be worth checking out. How old/what mileage was the Simrad unit? Thanks
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Old 30-06-2016, 05:36   #19
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Re: Autopilot wiring question

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Originally Posted by Neptune's Gear View Post
Ben, it depends on the pump. For example, the Simrad RPU 160 can draw up to 47 amps (at stall), but of course it virtually never gets that high. Cables, and a circuit breaker, must be sized to suit that max load. A thermal circuit breaker can be used so that, for example, it will allow stall for 5 secs (or whatever) then flip the circuit breaker if the load is still there. Of course short or higher load should never happen, and would overload the circuit breaker more quickly.
Soft start - it should be smooth now - the AP software should start the motor slowly for minor corrections, and faster for major ones. If it is not doing that, the motor could have an issue (Has it had brushes/bearings replaced etc)
The H bridge I have used is from Robot Power Products - Simple-H & HV - H-bridge and you can read on that page about others who have solved the issue with one of these.
Cheers
Matt
Wow Matt, thats some serious Amps. Thanks for the heads up on that. It would be interesting to find out what drive the folks have. I guess to properly match the cable and breaker to the unit this is going to be needed. Though without a H bridge it is limited by the software to 20 amps, but I have no idea what sort of averaging or duty cycle the navman 3380 uses when setting the 20 amp limit.

To me the unit seemed a bit jerky, but to be honest I really havent used many bigger Autopilots. They always seem to be broken when I get aboard... I am more a windvane kind of guy, so this is all an interesting and useful learning curve for me. As far as I know the motor is all original.
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Old 30-06-2016, 08:47   #20
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Re: Autopilot wiring question

Like others have said your wiring may not be large enough to prevent voltage drop/overheating for the longer run from the panel to the AP. If it were my boat I would put an adequately rated relay using the same wiring that was used to go to the AP from the panel as the control circuit. It would be grossly bigger than required but you would not have to pull it out and then pull new wire. You could then do that (or not) in the future.

It is very handy to be able to turn off the autopilot from the panel in my mind. I would have a spare relay on hand as they can fail although not very often. They are easy to replace. I would not use the potential of a failure as a reason not to use one. But that is just if it were my boat.

You would certainly need to put a properly rated fuse from the battery to the relay power circuit and the wire to it and to the AP would have to be the proper size for the draw. For the AP I would go up a size perhaps.

I appreciate a working AP very much when offshore so I would want it to work with the least problems 24/7.

Many of the other suggestions are good to. Your choice.
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Old 30-06-2016, 16:34   #21
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Re: Autopilot wiring question

Yes, the problem is running it to the panel adds about 30 to 40 foot of extra wiring. The funny thing is when it was first run up it failed while motoring, with the higher voltages and workes while sailing. So if anything maybe the problem was voltage spikes due to some combination of alternator, battery combiner/autohelm interaction? Weird.. but I still think big wires right back to the batts will reduce any of these spikes or crashes?

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Old 30-06-2016, 18:49   #22
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Re: Autopilot wiring question

Many VOM's have a min-max setting for monitoring fluctuations.
Fluke 87 for instance.

http://www.fluke.com/fluke/uses/comu...gemeasurements
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Old 30-06-2016, 19:50   #23
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Re: Autopilot wiring question

Ben, one other possibility when t hings seem to change without reason: I've had a circuit breaker go bad in the past. Did not trip out, but the internal resistance became much higher and voltage drop greater.

Our NavMan 3100 pilot is pretty stable, handles startup loads ok and has never had issues with over-voltage... only over-current or low voltage (which tends to encourage over-current). Don't know what the difference between the two models might be, though.

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Old 30-06-2016, 20:11   #24
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Re: Autopilot wiring question

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Very interesting Raymond. The unit hasn't seen that much use, maybe a few thousand miles or so, so hopefully it is not to bad, but then you never know. Might be worth checking out. How old/what mileage was the Simrad unit? Thanks
The boat is 20 years old, was built in the U.S. and purchased in Israel then sailed back to Australia across the Atlantic and Pacific oceans so it had probably had a fair bit of time in service. The pump and ram are unitized and it's a fairly industrial looking unit with a decent sized motor.

If you want to monitor voltages at the supply to the autopilot an analogue voltage meter such as the QP5020 from Jaycar might provide a better indication than a digital meter.
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Old 30-06-2016, 20:31   #25
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Re: Autopilot wiring question

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Originally Posted by Cap Erict3 View Post
Many VOM's have a min-max setting for monitoring fluctuations.
Fluke 87 for instance.

http://www.fluke.com/fluke/uses/comu...gemeasurements
Thats the kind of thing thats probably going to be needed to isloate the issue. So much better than my $5 multitester!

Jim, thanks for that, good to know your navman 3100 is working well. Its is interesting that you notice the amp draw go up with reduced voltage. I think I read somewhere that the extra amps on startup is proportional to the square of the voltage drop. So if I have it right then a small voltage drop can cause a much bigger amp increase.

What sort of wiring and circut breaker do you run on yours, and what sort of peak amperage do you get? I guess your steering loads will be much less than the maids, but at least she is a similar length.

Thanks all for your various inputs. Every bit helps me learn more about common issues, and possible problems and solutions. Cheers
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Old 01-07-2016, 10:02   #26
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Re: Autopilot wiring question

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Originally Posted by Snowpetrel View Post
Yes, the problem is running it to the panel adds about 30 to 40 foot of extra wiring. The funny thing is when it was first run up it failed while motoring, with the higher voltages and workes while sailing. So if anything maybe the problem was voltage spikes due to some combination of alternator, battery combiner/autohelm interaction? Weird.. but I still think big wires right back to the batts will reduce any of these spikes or crashes?

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Snow, you certainly want to troubleshoot and fix your immediate problem. Doing what I suggested would be a good thing even if it doesn't correct it. It may well do though.

A min-max voltmeter might give you some interesting info. You would have to watch it while using the AP to know when it happened and relate it to how it works. You shouldn't be having big voltage spikes from your existing systems in any case. Not good for equipment in general, if that is happening.

Hope you get it sorted out. Mysteries like this can be maddening if you can't isolate and fix it in the near term. Good luck.
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Old 01-07-2016, 10:27   #27
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Autopilot wiring question

A fairly common issue is the rudder travel reaching the stop.

I can't really equate that to overloading under power but not under sail.

One thing I have found in my many years of chasing gremlins is to look to the moving parts. Bearings, bushings, motor brushes, potentiometers.

I converted a Raymarine Wheel pilot using an SPX5 core and a low power consumption piston pump and have been very satisfied. Pump price is reasonable too.

Measured running current is around 5 amps.

http://octopusdrives.com/reversing-piston-pump

A little tip. Never adjust flow rate on a system w/ a pressurized reservoir without bleeding pressure off.
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Old 01-07-2016, 23:42   #28
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Re: Autopilot wiring question

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Jim, thanks for that, good to know your navman 3100 is working well. Its is interesting that you notice the amp draw go up with reduced voltage. I think I read somewhere that the extra amps on startup is proportional to the square of the voltage drop. So if I have it right then a small voltage drop can cause a much bigger amp increase.
G'Dau Ben,

Well, I have made no measurements that show that the current goes up at reduced voltage... pretty hard to do outside of a lab setup. I based my statement on the simple relationship between power required and Ohm's law: to get the same power at lower voltage, more current is needed.

Quote:
What sort of wiring and circut breaker do you run on yours, and what sort of peak amperage do you get? I guess your steering loads will be much less than the maids, but at least she is a similar length.
30 A breaker, and I don't know the wire size offhand, for it is a relic of the builder/PO and I have never checked it. However, I've checked the voltage at the motor under modest load and the drop is not excessive. The drive is an older Whitlock, way oversized for this boat, and it is a power hungry sucker for sure. The bloody clutch draws 2 amps! But it is truly powerful... one should never reach through the wheel while a/p is driving! But anyway, there is a 20 amp internal fuse in the brain box, and that is hard to replace so I have set the software trip point at 18 amps. Very occasionally we get a trip out from that... usually at an awkward moment, surfing down a big wave with rocks nearby... and the bloody thing just lets go of the wheel and squeals loudly, as do I. Happened once as were gybing to round Cape Sonnerat and that was kinda exciting!

I wouldn't mind downsizing the drive, 'cause it is hard to feed at sea, but the cost of replacement has deterred me from that rash move.

Cheers,

Jim
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Old 02-07-2016, 01:36   #29
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Re: Autopilot wiring question

^^ thanks Jim, thats really useful info, given the similar boat size and units. I dont think the 3380 has the internal fuse, but it does have a software trip that can adjusted. Even on its max value of 20 amps it trips when sailing in moderate conditions, say 25 knots on the beam. With an easy rig.

Thats one thing I am not used to is the way these things trip out and totally let go. At least we were in open ocean so it wasnt quite so bad, but it seems pretty dangerous, as your example shows. It really erodes your confidence when the AP can trip at any moment, and normally at the worst time, when you are on the foredeck!

I am used to windvanes that have faults, but they while they may steer poorly at times at least they keep trying, and fail gracefully with plenty of warning. Unlike the AP, which is great, until suddenly it ain't.

It is good to know a 30 amp breaker does it on yours. At some stage they are going to reconfigure the spare HF radio wire to run the AP. It has a 30 amp fuse, so hopefully that will work a good bit better for them.

Cheers Ben

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Old 03-07-2016, 01:29   #30
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Re: Autopilot wiring question

^^^
Ben, while the Maid and I-2 are about the same OAL, I-2 light ship weight is ~9.5 tonnes. I suspect that the Maid may be heavier (!). And our rudder is essentially a spade with a rather narrow partial skeg and some balance area... normally pretty damn light to steer. The only times that the rudder loads up are when at large heel angles to windward or when the stern is influenced by big waves from astern. So I'm not sure that the analogy is very true between the boats. And, of course, different drives... perhaps a more telling difference that anything else. The Whitlock is designed (I believe) for trawlers and other vessels with heavy helms and unlimited electrical power, an attribute that we do not share!

Hope that John and Barb are enjoying the long white cloud... from the MSLs, the wx down there hasn't looked to flash!

Jim
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