This type (or similar) of limit switch could work as it has 75 degrees over travel and 10 degrees differential on the switch.

https://www.ebay.co.uk/itm/ME-8104-...381461?hash=item26006513d5:g:RpMAAOSw0ABanS-5

For interest here is a library image of the steering quadrant that I am working with. I will most likely have to fabricate a plate for the middle of it to mount the ram end to.

https://www.westerly-owners.co.uk/westerlywiki/index.php?title=File:Old-quadrant.jpg

The image makes access look good but it certainly is not like in the image!

 

I've just had an email from the second ram supplier (very helpful and very easy to communicate with unlike the first one) and he says that the ram manufacturers do the same ram with a 50 watt motor which means that the H-Bridge would not be needed. I'll need to see the exact specs of the ram first before I committed to it.
On a separate note I noticed when sailing today that my autopilot control head was an Autohelm 4000 and not a 3000. Although I think this makes no difference unless someone knows different.

 

This is the drive circuit of a 4000 model its very similar.

 

The H bridge FETs are rated at 140W @25 deg C, 45A @ 100 deg C. So that 50W ram should be ok.

 

Thanks for that info debe. The ram specification says:

Typical Current Intermittent (350KG) 14.0A.

I seem to recall that the recommended fuse rating for the Autohelm 4000 is 12A. Then again if the ram were to ever be putting 350kg of force on the aluminium steering quadrant I think I might quite like it if the fuse blew! This could happen if a limit switch failed I guess. Worst case is if it blows the fuse regularly in normal operation then I have to fit the extra H-Bridge.

I'm not so strong on electronics diagrams but I think I get the general gist of the one you posted. I notice in the top left there are connections labelled as 'Clutch Driver'. Is it possible that the ST4000 could operate the clutch on the ram without me needing to create a separate switched circuit?

I haven't opened up the ST4000 in years (not since the compass fell off its mounts) and I'm not keen to do so right now to see what is inside it connection wise as I need it to get me through a few hundred more miles of sailing back to my winter berth.

 

The clutch drive is a BUZ71 FET max 13A @ 25 deg C probably with a heatsink. If you look at the MD1&2 motor outputs they are PWM. There appears there is a Rudder reference P8/9/10, & the C+/C- Clutch output. Just out of curiosity was the wheel drive the same as in the picture?

 

Yes that looks like the wheel pilot. It has had two in its time. The earlier black one and now the later model grey one. I note however that the list of connections you show is for a Autohelm 4000+ which I believe is the later grey much smaller lower profile autopilot head with a digital display.
Mine is like the image attached.

 

Hello,

Came across this post when searching for the Autohelm 4000 electric circuit. Even thouhg it seems Ineed to continue my search I'm curious how it went with the autopilot?

Cheers

 

Hi dave,
Very old thread, the Thread starter not seen since 2018, please start a new Thread.

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