B&G Focus 6 blade Paddlewheel Log

N

NorthRising

Well-Known Member
Joined
30 Mar 2009
Messages
411
Location
North - Sonata
Visit site
3 weeks back whilst going against the tide I glanced at the boat speed through the water on the Focus display as we were not doing much over the ground. The log suggested we weren't doing more than 2 knots through the water, the wake trail suggested otherwise. I then observed the log speed reading dwindle over a few seconds to zero, and at that it has remained since. The paddle wheel is not fouled and spins freely (or it did until I removed it).

The log is old B&G focus which came with the boat as new to me and until now has been reliable: The sensor is part 202-00-045 (discontinued) and the paddle wheel spares kit is 202-00-54 (available at over £60), both as per page 3 in: http://www.bandgservice.co.uk/documents/ProductIDGuidev2.12.pdf

So the question is whether the problem is with the paddle-wheel or the through hull sensor unit (the body in which the paddlewheel is mounted)? I've found a little bit on how to test: http://forums.sailinganarchy.com/index.php?showtopic=93429 "...You can test the speed sensor using the green wire in the service cable, the signal relative to B- should toggle between 0 volts and approx 5 volts (one pulse for each wing passing the magnetic switch)...". However, I'm expecting to find that I don't get a signal back as described and I'd still be unable to know whether the cause of the problem is the wheel or the sensor, and £60 plus is steep (for me) as a means of testing to find out the sensor is destined for disposal.

Any ideas? Or do I have to face the facts that its time for instrumentation re-fresh (really hope not as skint and the echo-sounder is functioning fine through to the Focus display unit.
 
Last edited:
Usual case for paddlewheels is one blade has a small magnetic iron bar in it which triggers the pulse when it goes past the sensor. I assume that's the case for this unit as it says you can replace the discontinued 6 blade wheel with a four blade wheel. Has the iron bar corroded away or fallen out? That happened to me on a NASA paddlewheel log but then a replacement wheel was only £6.

If it has gone then you could try and replace it with another small magnetised bar sealed in with epoxy.
 
Looking at the paddlewheel each blade seems to have a magnet and all six are in place; so I'm leaning toward it being a sensor issue. I will run the voltage test on the green wire in the service cable and try passing a magnet through the slot and then with the paddlewheel back in place and see where that leaves me in terms of diagnostics.

The guide actually says I could replace the discontinued sensor 202-00-045 with a SEN-SPD-HP (presumably compatible with the B&G Focus display unit), as far as I can see that is different from simply substituting in a four blade paddlewheel; but it could end up being the way forward unless I can source a trailing log online.
 
andygc said:
It might be worth your while talking to Tinley Electronics http://www.tinleyelectronics.com. I found them very helpful when I had a problem with my (older than yours) Focus system.
Click to expand...

The quote I have, is from Tinley to whom B&G service section forwarded my enquiry. I'll see if I get any reading out of the green service wire on the weekend, and then have a think; my personal take the more I consider things is that it is likely that there is nothing wrong with the wheel itself and that the error rests in the sensor or wiring, but we shall see.
 
Update:

Somewhat to my suprise, sticking a multimeter between the green wire in the service cable and the negative bus bar shows a steady 4.49 volts when the paddlewheel is stationary and the voltage drops each time a blade passes through. So that is a wire designed to carry raw speed data from the display circuit board to Focus wind instrumentation, and it appears to be carrying exactly that.

So the green wire from the log gets a signal to the board, and the board supplies a signal to the green service wire which can clearly be seen varying on multimeter as the paddlewheel rotates, yet the instrument display stubbornly displays zero knots and the logged distance does not increase.

So that I think tells me the paddlewheel and transducer are functioning just fine but for some reason the display is Donald ducked and is displaying value zero rather than "- - -" for no signal, hmmm.

So I removed the plug from the back of the display panel opened it up all wires seem connected pushed it around a bit, closed it up, opened up the display unit, took circuit board out, put it back, plugged it back in no difference.... depth reading fine , speed zero knots.

It looks like re-instrumentation then...
 
Last edited:
You must log in or register to reply here.

Share this page

Top