Autohelm 3000

[bob leonard]

I have an autohelm on my new Pearson 36 (1985). Had the boat for 4 years. I put the autohelm to work for the first time this year. All the control buttons work very well. Motor works well. It will track for about 1 or 2 minutes, then if I make a one degree or 10 degree correction in either direction, it just keeps correcting in that perspective direction for ever. I have heard that one can steer to boat in a circle in both clockwise and counter clockwise directions and this should calibrate the unit. If I take it off its' mount and turn it by hand in each direction instead of driving the boat in both directions, shouldn't this calibrate the unit? How would the unit know how it is turning? I tried this procedure and it doesn't work. Any help out there in blue water land? would really appreciate any help!!!!!!!!!!
Thanks
Bob

[Tia Bu]

I have the analog version of this autopilot, with a round, compass dial rather than the push buttons. It seems to get 180 degrees out of whack sometimes when I first turn it on. Spinning the compass dial through 360 degrees seems to straighten it out.

I wonder if spinning your compass unit around through 360 degrees would help it find its way?

Good luck. It's a good autopilot once it gets its bearings.

[Adventurebound]

I have the smaller one. You turn the boat to do a slow turn taking minimum 1 and a half minutes. Calculates and compensates for compass deviation so the whole boat has to turn. Other controls are adjusted for best performance. Check your manual how to do the whole setup.

[Mystic38]

the manual is available online I am sure, attempt to calibrate it. sounds like you may not have a heading sensor installed...

[GordMay]

Greetings and welcome aboard the CF, Bob.

Do you have the manual?
➥ http://www.raymarine.com/view/?id=1836

[jfhspike]

I know it's a couple of year since this was asked, but I have the same problem more or less. My personal suspicion is that one of the capacitors in the circuit has started to die; that would be consistent with the fact that the trouble shows up after several years, and with the slow turn in one direction ... a steadily discharging cap could certainly cause this in many circuits that I can imagine.

Then again, having taken apart my autohelm and looked at it, I doubt it'd be easy to figure out which cap was bad...so maybe this is useless. Still, the deeply committed could search for capacitors on the board -- esp. larger ones, with ratings in the microfarad or even millifarad range rather than the ceramic pico-farad ones -- and try swapping in replacements.

[sailorchic34]

Originally Posted by jfhspike

I know it's a couple of year since this was asked, but I have the same problem more or less. My personal suspicion is that one of the capacitors in the circuit has started to die; that would be consistent with the fact that the trouble shows up after several years, and with the slow turn in one direction ... a steadily discharging cap could certainly cause this in many circuits that I can imagine.

Then again, having taken apart my autohelm and looked at it, I doubt it'd be easy to figure out which cap was bad...so maybe this is useless. Still, the deeply committed could search for capacitors on the board -- esp. larger ones, with ratings in the microfarad or even millifarad range rather than the ceramic pico-farad ones -- and try swapping in replacements.

Probably it's the two below the + wire to the motor, They are in series with one enother and connect from motor + to ground.. I just had both melt on me a few weeks back. Replaced them with 45mf electrolic caps and also changed the two darlingtons at the bottom, one tip120, one tip 125.

Odds are one of the darlingtons needs replacing. Sometimes changing all 4 does the trick too.

What happens is one darlington will burn out and it only turns in one direction. There are two tip120's and two tip125's that control forward and reverse. two for forward and two for reverse. Keep a handfull aboard and they are cheap off Ebay.

Good luck.

I added a wireless remote to my autohelm 3000 too for $14. Works really well. Instructions -> http://www.cruisersforum.com/forums/...-a-168163.html

Enjoy.

[jfhspike]

Wow...great information. I suspect that those first two are filter caps, there to help damp out any ripple in the supply voltage. As for the Darlington pair...it does seem like a pretty likely problem, but I doubt it's the case here, for at least on my unit, the thing mostly works fine for the first 30 seconds or so, happily running the motor either clockwise or counterclockwise when I move the control head on the workbench. But when I set it in one position for a few minutes, and it "settles on a course", at first it's fine: the motor sits perfectly still, as you'd expect. And then it begins to "chirp" with a tiny turn to starboard...a few seconds' wait...another chirp to starboard ... and so on.

To me, this sounds like the "I" part of a PID control system going wrong. It's trying to ever-so-slightly offset the effects of weather helm or something. The two possibilities here are either (a) compass drift, so that the input signal to the PID part of things is wrong, or (b) a miscomputed integral in the "I" part of the PID controller. Since integration is usually done electronically with capacitors, my guess is that there's a bad cap somewhere.

Then again, maybe the integration is all done digitally, and I'm completely off base. Still, I'll pick up a couple of TIP 120 and 125s to carry in my spares pack.

[sailorchic34]

Originally Posted by jfhspike

Wow...great information. I suspect that those first two are filter caps, there to help damp out any ripple in the supply voltage. As for the Darlington pair...it does seem like a pretty likely problem, but I doubt it's the case here, for at least on my unit, the thing mostly works fine for the first 30 seconds or so, happily running the motor either clockwise or counterclockwise when I move the control head on the workbench. But when I set it in one position for a few minutes, and it "settles on a course", at first it's fine: the motor sits perfectly still, as you'd expect. And then it begins to "chirp" with a tiny turn to starboard...a few seconds' wait...another chirp to starboard ... and so on.

To me, this sounds like the "I" part of a PID control system going wrong. It's trying to ever-so-slightly offset the effects of weather helm or something. The two possibilities here are either (a) compass drift, so that the input signal to the PID part of things is wrong, or (b) a miscomputed integral in the "I" part of the PID controller. Since integration is usually done electronically with capacitors, my guess is that there's a bad cap somewhere.

The square box 3000 is digital with analog input from the heading sensor poles and also anolog input from the button pressed (which is weird). Also make sure there isn't near by magnetic screwdrivers, etc that may be effecting the heading sensor. It would not take much.

Then again, maybe the integration is all done digitally, and I'm completely off base. Still, I'll pick up a couple of TIP 120 and 125s to carry in my spares pack.

Actually it may be working fine. If you engaged the autopilot, then moved it around and put it back on the bench with the old heading, it is still trying to turn the bench to the original heading. Have it sit in one place, hit standby and then hit auto. if it does not turn then, it's fine.

The old 3000 was a dumb autopilot it only compairs the heading value with valued stored when auto was pushed. When you press a 1 degree turn, it expects the boat (or bench) to turn. As it's not turning, it's giving a bit more rudder every so often as it should. If you turn it left and right and the motor turns right and left it's working fine

[jfhspike]

Actually, my "old" autohelm is even older: it's the round one with the compass-dial on top. And I'm pretty sure it's NOT working right, because when I head WNW from Woods Hole towards Newport, eventually it ends up steering the boat NW, then N, then NE, and even E (if I don't get sick of its foolishness by then).

On the bench, I'll set a course (both red and green lights go out) and then wait for it to start "ticking" to starboard, and then turn the unit in the direction that causes it to actually steer a tiny bit to PORT, and then wait...and a few minutes later, I'm "ticking" to starboard again. If this were just an "off by a tiny bit" error, I'd expect it to sometimes tick to PORT, but that never happens.

I'm pretty certain that the algorithm looks something like "compute difference d between desired heading and current heading. Compute P = cd, where c is some constant (adjusted by the little dial on the bottom of the unit, too!), and run the motor for a period of time proportional to P. But at the same time, compute I = integral of d over time, and actually run the motor for a period of time proportional to P + I. (clockwise if positive, ccw if negative)."

This is more or less PI control. I'm pretty sure there's a deadband in there ("do nothing if the scheduled motor run-time is smaller than some constant K"), with the constant K controlled by the "sea state" switch. And in at least one version, there seem to be four wires to the motor, and I'm guessing that one pair measures the load and says "If you're trying too hard, stop trying!" to avoid the motor pushing against the end-stops for the wheel.

--J

[sailorchic34]

Originally Posted by jfhspike

Actually, my "old" autohelm is even older: it's the round one with the compass-dial on top. And I'm pretty sure it's NOT working right, because when I head WNW from Woods Hole towards Newport, eventually it ends up steering the boat NW, then N, then NE, and even E (if I don't get sick of its foolishness by then).

On the bench, I'll set a course (both red and green lights go out) and then wait for it to start "ticking" to starboard, and then turn the unit in the direction that causes it to actually steer a tiny bit to PORT, and then wait...and a few minutes later, I'm "ticking" to starboard again. If this were just an "off by a tiny bit" error, I'd expect it to sometimes tick to PORT, but that never happens.

I'm pretty certain that the algorithm looks something like "compute difference d between desired heading and current heading. Compute P = cd, where c is some constant (adjusted by the little dial on the bottom of the unit, too!), and run the motor for a period of time proportional to P. But at the same time, compute I = integral of d over time, and actually run the motor for a period of time proportional to P + I. (clockwise if positive, ccw if negative)."

This is more or less PI control. I'm pretty sure there's a deadband in there ("do nothing if the scheduled motor run-time is smaller than some constant K"), with the constant K controlled by the "sea state" switch. And in at least one version, there seem to be four wires to the motor, and I'm guessing that one pair measures the load and says "If you're trying too hard, stop trying!" to avoid the motor pushing against the end-stops for the wheel.

--J

OK the round analog version is very old. It probably is a capacitor. I think the motor is only two wires. Probably easier to buy a autohelm 3000 or 4000 control head on ebay for $250 and use the motor with it.

[jfhspike]

Nah...long before I'd do that, I'd just build my own, based on an arduino and an H-bridge (and perhaps a wireless fob like yours!), assembled in a waterproof box with a display showing through a lexan "window" or something. With a fluxgate compass and accelerometer, I can use a Kalman filter to get a pretty darned accurate heading measurement and after that, it's all just PID control stuff as you know. To be honest, I mostly use the AP for one of three things:

* sailing or motoring in the fog, when it's really helpful to have a "helmsman" who can follow a course while I spend my time navigating and listening and watching

* raising/dropping sails

* long overnight passages in more or less calm weather in the Gulf of Maine.

None of these requires a whole lot of sophistication.