Difference between Raymarine Autopilots?

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maby

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Does anyone know for sure the difference between the various Raymarine autopilot control units? I'm planning on fitting one this spring and, looking through the prices and specifications, the only obvious difference between the ACU-200 and ACU-400 is the current it can source, but the price is about £600 vs. £1,200. I'm not normally a mean beggar, but this did get me thinking - can I use the cheaper unit and insert a relay to control the actuator? Is the control circuit a simple on/off, or does the ACU provide variable drive to the actuator? If the latter, then it would be a lot more difficult to accurately boost the output current but, if it's simply turning the drive motor on and off, then I can easily insert a relay and drive the higher current motor.
 
aluijten said:
If memory serves me right the simpler one does not support the electric clutch as the base model autopilot have a manual clutch (not a below-deck installation).

Cheers,

Arno
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That is true of the ACU-100 and ACU-300, but the specification of the ACU-200 only seems to differ from the ACU-400 in terms of current output capacity and the ACU-400 includes "Digital Input/Output" whatever that is. See http://www.raymarine.co.uk/view/?id=7725&collectionid=82&col=7717
 
maby said:
That is true of the ACU-100 and ACU-300, but the specification of the ACU-200 only seems to differ from the ACU-400 in terms of current output capacity and the ACU-400 includes "Digital Input/Output" whatever that is. See http://www.raymarine.co.uk/view/?id=7725&collectionid=82&col=7717
Click to expand...

The digital input output may be either related to a CAN-bus connection to engine control, or may have to do with a new feature were the steering servo is proportionally controlled. So basically the speed of the servo is regulated. Having looked at the website of Raymarine it seems they are lagging behind in the updates of the manual downloads....

So you may be able to use an external power-relay to handle the currents. But there may also be a difference in the expected lock-to-lock times for the servo. I don't know.
Maybe send them a message?
 
aluijten said:
...
Maybe send them a message?
Click to expand...

Hmmm,

"Dear Raymarine Support,

I would very much like to avoid paying your ridiculously inflated prices by lashing a £5 relay onto the output of your £600 ACU rather that handing over £1,200 for the high power model. Could you please tell me if this will work and, possibly, suggest a suitable relay?"

Not confident of getting an honest answer! :)
 
maby said:
Hmmm,

"Dear Raymarine Support,

I would very much like to avoid paying your ridiculously inflated prices by lashing a £5 relay onto the output of your £600 ACU rather that handing over £1,200 for the high power model. Could you please tell me if this will work and, possibly, suggest a suitable relay?"

Not confident of getting an honest answer! :)
Click to expand...

I don't think you should enter the political arena with these kind of support questions.

You could try:

"Dear Raymarine, I'm confused about the differences between model X and Y as your website has limited information about it. For example what is the purpose of the digital IN/OUT?"

Anyway, I am not sure if the servo output is simply a 0 and 12 volt output. It may be a PCM regulated output, depending on the drive.
For myself I have an older model and I have the distinct impression the servo motor can be actuated at different speeds, judging by the noise it makes.

Again, I would use a fairly open question towards Raymarine to figure out the differences. If the answer is not clear, nothing gained or lost, if you do get a sensible answer you can make a better evaluation.
 
aluijten said:
I don't think you should enter the political arena with these kind of support questions.

You could try:

"Dear Raymarine, I'm confused about the differences between model X and Y as your website has limited information about it. For example what is the purpose of the digital IN/OUT?"

Anyway, I am not sure if the servo output is simply a 0 and 12 volt output. It may be a PCM regulated output, depending on the drive.
For myself I have an older model and I have the distinct impression the servo motor can be actuated at different speeds, judging by the noise it makes.

Again, I would use a fairly open question towards Raymarine to figure out the differences. If the answer is not clear, nothing gained or lost, if you do get a sensible answer you can make a better evaluation.
Click to expand...

Hmmm, may do - hopefully they don't read this forum!

I can cope with PCM too - just use big power FETs rather than mechanical relays. I can't imagine that they would use a true analogue drive - we're talking ten, twenty, thirty amps - the heat dissipation would be horrible. Is there anyone out there with a recent Raymarine ACU and an oscilloscope?
 
bigwow said:
maby said:
Hmmm, may do - hopefully they don't read this forum!
/QUOTE]

They do:encouragement:
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Feared as much! In fairness, if I had thought there was any way that I could ask them the question without them twigging, I wouldn't have started this thread. I guess the alternative approach is to talk to one of the manufacturers of compatible actuators - they must know the type of drive coming out of the ACU and have no particular interest in which ACU I buy.
Click to expand...
 
Thanks to another helpful soul on this forum I managed to find the answer to the question how the autopilot servo is controlled:

Quote from the service manual of the 150 Course Computer:
"Speed control is achieved by modulating the drive voltage at 20KHz for various duty cycle settings"

I would be very surprised if they changed anything significant in this principle for the last generation of systems.
 
P.S. - is that as a result of the thread running today on the archive of raymarine service manuals? I had it in mind to trawl through that later today in search of the answer...
 
So now, it's just a case of deciding how much confidence I have in my ability to get it working based on a 30 year old degree in electronics that has not been used much in the intervening period! There's six hundred quid to be saved if I can make the buffering work - and I have the circuit diagram of the output stage of the previous generation of autopilot... Of course, if I fail, I could be left with a six hundred quid ACU that I have to offload on eBay and then pay the twelve hundred! :)
 
P.S. it's a pity that web archive does not include the service manuals for the ACU-200 and ACU-400 - I bet the circuits are virtually identical with just higher power output stages in the 400 - may even be possible to swap the transistors!
 
maby said:
Of course, if I fail, I could be left with a six hundred quid ACU that I have to offload on eBay and then pay the twelve hundred! :)
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And don't forget that find out you've failed halfway a sailing trip may be annoying as well :(
You could also try to source a second hand or surplus stock older model instead of going for the new shiny package....
I'm not so sure the new model will be such an improvement over the slightly older model.
 
aluijten said:
And don't forget that find out you've failed halfway a sailing trip may be annoying as well :(
You could also try to source a second hand or surplus stock older model instead of going for the new shiny package....
I'm not so sure the new model will be such an improvement over the slightly older model.
Click to expand...

Hmmm, decisions, decisions! In fairness, if you are correct that they will not have changed the design of the output stage, then it really should be very easy - I even have the circuit diagram of the output stage of a previous generation ACU for a type 2 drive unit - and they haven't changed the drive units, just the ACU, so the drive requirements really cannot have changed! It does bug me that they are charging twice the price when the only apparent difference is a higher current output stage.
 
maby said:
Hmmm, decisions, decisions! In fairness, if you are correct that they will not have changed the design of the output stage, then it really should be very easy - I even have the circuit diagram of the output stage of a previous generation ACU for a type 2 drive unit - and they haven't changed the drive units, just the ACU, so the drive requirements really cannot have changed! It does bug me that they are charging twice the price when the only apparent difference is a higher current output stage.
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I do agree the difference in price is a bit steep. Of course the bigger one can also run on 24 volt, so that is another difference.

What is was wondering about is how this setup works if you have an hydraulic system with a continuous running motor and reversing valves. I seem to remember you can use one of those servo's as well on this computer.
It seems to me that using PCM speed control might become a bit of a problem then.
 
maby said:
It does bug me that they are charging twice the price when the only apparent difference is a higher current output stage.
Click to expand...

Not unusual. Market segmentation doesn't have to be based on sound technical reasons.

A friend of mine who's into cars tells me that there's a whole range of BMWs with increasingly powerful engines, which are in fact the same engine with different firmware installed in the control chips. It's cheaper for BMW to make it that way rather than maintain lots of different parts and production lines. There was a model of PC CPU which came in two versions, with and without a maths co-processor. In fact they all had the co-processor inside, but the cheaper version had it disabled, again because it was cheaper to make it that way than have two separate parts. Some things are actually identical, but branded and marketed differently to appear as a "budget" and "premium" option.

The first part of this rambling old blog post explains what they're up to (apologies for egg-sucking if applicable): http://www.joelonsoftware.com/articles/CamelsandRubberDuckies.html

Pete
 
prv said:
Not unusual. Market segmentation doesn't have to be based on sound technical reasons.

A friend of mine who's into cars tells me that there's a whole range of BMWs with increasingly powerful engines, which are in fact the same engine with different firmware installed in the control chips. It's cheaper for BMW to make it that way rather than maintain lots of different parts and production lines. There was a model of PC CPU which came in two versions, with and without a maths co-processor. In fact they all had the co-processor inside, but the cheaper version had it disabled, again because it was cheaper to make it that way than have two separate parts. Some things are actually identical, but branded and marketed differently to appear as a "budget" and "premium" option.

The first part of this rambling old blog post explains what they're up to (apologies for egg-sucking if applicable): http://www.joelonsoftware.com/articles/CamelsandRubberDuckies.html

Pete
Click to expand...

All quite true - been there myself on occasion, but it doesn't stop it being a pain when you are on the receiving end! If I could get the drive for a type 2 servo out of an ACU-200 for the addition of half a dozen high current MOSFETs on a heatsink, then I'm up for it!
 
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