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24v Raymarine Linear Drive Clutch Opperation by NAC-3

Chris Doucette
 

Hello everyone,

I have had to replace my Old Raymarine ST7000 + autopiliot computer.  I have gone with a NAC-3 B&G- as many of my new instraments are B&G and I want the integration.   As such, I have run into a hickup with setting this up with my existing Raymarine Type 2 Long Linear Drive 24v- a solid and well working device I do not want to spend 2K replacing.     I did some research and the NAC-3 will handle this drive unit.  HOWEVER, it appeas that the CLUTCH on this unit is 12v.  In fact, Ray always uses 12v on their clutches irrepective of the drive voltage (24 or 12) and the Ray autopilot units have a 12v /24v selector for the clutch wires.  This is where i got stuck.  The NAC-3 only sends nominal (24v or 12v) voltage to both the drive and the clutch with no way to selecting a differing voltage for the clutch.  The voltage the drive gets, is what the clutch gets.  So to keep my Raymarine drive unit I need to send the cluch 12v.  

My proposed solution.  Being the cluch is 12v and draws a maximum of 3A and I know that the NAC3 can provide that amporage, I plan on involving in-lining a simple 24v to 12 step down converter/regulator in the clutch curcuit a as like this one... https://www.amazon.com/Kohree-Converter-Regulator-Waterproof-Transformer/dp/B0756W6V4F/ref=sr_1_2?dchild=1&keywords=Kohree%2BDC%2FDC&qid=1615838251&sr=8-2&th=1  I do believe this will work..   So my quest to you is this- any major flaws in this or consideration / solutions that I am overlooking?  Thanks!  

Chris
S/V Amarok SM385
CW Bill Rouse
 

I think your plan is fine, but I would use a Victron 24 to 12 volt converter. Remember your autopilot is only as good as your weakest link. 

Best,

CW Bill Rouse 
Amel Owners Yacht School
+1 832-380-4970 | brouse@...
720 Winnie, Galveston Island, Texas 77550 
www.AmelOwnersYachtSchool.com 
Yacht School Calendar: www.preparetocastoff.blogspot.com/p/calendar.html


   


On Mon, Mar 15, 2021, 3:02 PM Chris Doucette <amaroksailing@...> wrote:
Hello everyone,

I have had to replace my Old Raymarine ST7000 + autopiliot computer.  I have gone with a NAC-3 B&G- as many of my new instraments are B&G and I want the integration.   As such, I have run into a hickup with setting this up with my existing Raymarine Type 2 Long Linear Drive 24v- a solid and well working device I do not want to spend 2K replacing.     I did some research and the NAC-3 will handle this drive unit.  HOWEVER, it appeas that the CLUTCH on this unit is 12v.  In fact, Ray always uses 12v on their clutches irrepective of the drive voltage (24 or 12) and the Ray autopilot units have a 12v /24v selector for the clutch wires.  This is where i got stuck.  The NAC-3 only sends nominal (24v or 12v) voltage to both the drive and the clutch with no way to selecting a differing voltage for the clutch.  The voltage the drive gets, is what the clutch gets.  So to keep my Raymarine drive unit I need to send the cluch 12v.  

My proposed solution.  Being the cluch is 12v and draws a maximum of 3A and I know that the NAC3 can provide that amporage, I plan on involving in-lining a simple 24v to 12 step down converter/regulator in the clutch curcuit a as like this one... https://www.amazon.com/Kohree-Converter-Regulator-Waterproof-Transformer/dp/B0756W6V4F/ref=sr_1_2?dchild=1&keywords=Kohree%2BDC%2FDC&qid=1615838251&sr=8-2&th=1  I do believe this will work..   So my quest to you is this- any major flaws in this or consideration / solutions that I am overlooking?  Thanks!  

Chris
S/V Amarok SM385
Clive Chapman
 

I don’t know anything about this specific system, but is the clutch a simple ‘on’ or ‘off’? If so, you could use a simple 24v relay using it to switch 12v to the clutch (assuming you can source as 12v feed of sufficient capacity from near by). Having said that, as Bill says you need good quality kit, so I don’t know if the price difference from the Victron step down, compared with a marinised relay is sufficient to justify.  
Bill Kinney
 

Installing a 24 to 12 volt convertor for this is like using a sledgehammer to kill a fly. It WILL work, but is  an insanely complex and expensive solution to a REALLY simple problem.  I am a very big fan of Victron equipment, but it really is not the right answer for this problem.

A relay is a bit better, but still much more complex a system than needed.

All you need is a resistor.  Measure the resistance of the clutch coil, and install a resistor in series with it that is as close as you can to match it.  If it costs more than $1 you are overpaying.

Ohm wrote the law. Take half the voltage drop across the resistor and half across the coil. 100% reliable. Just chose the right resistance and power rating.

We have been sailing for 5 years with a B&G 24 volt clutch output feeding a raymarine drive just using a 25 Watt/30 Ohm resistor (over kill, but it was so cheap not worth fine tuning) in series to take half the voltage drop.  The clutch is happy, the drive computer is happy.  I am happy because the whole setup cost $0.89 and has no failure modes I can see.

Keep it simple.
Chris Doucette
 

Update-

NAC-3 is up and opperational!  Thank you for all the feedback-  a quality  25 Ohm resistor did the trick! Shore provisioning complete :). 
Darren Gamble
 

Hi Chris

i have just brought the Nac 3 computer and will need to solve the clutch operation, could you share with me what specific brand, type of 25Ohm resistor you used? 
 Cheers Darren
SV Wanderer, SM 283
Chris Doucette
 

HI Darren,

I used one of these found on Amazon 25Ohm worked me.
https://www.amazon.com/gp/product/B089Q88QPN/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

Chris 
Amarok, SM385
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