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Depth reading wrong

vas

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21 Jun 2011
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Volos-Athens
guess you came across this thread on arduino board:
Depth Ultrasonic Water Transducer

some specs are there, guess you ignore the issue on how you pump all that 600 or so W to the xducer and only focus on dealing with the return signal, which is going to be interesting if the pulse originates from the headunit (as it should be I gather) and then the headunit does the timekeeping and the calcs to see how long it takes for the signal to return.
Doesn't look v.straightforward tbh as you somehow have to grab the high pulse, start a timer, receive the return pulse, get the diff.
The rest is easy :rolleyes:

seems to be exceptionally hard (at least for my knowledge!)
Mind, could it be that the headunit failing to send the 600W pulse be the culprit?
Maybe open the headunit up and see how it looks inside? corrosion/water ingress/tired or damaged components, failing capacitors?

goodluck!
 

John the kiwi

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23 Nov 2011
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Nelson New Zealand
Speaking to Hudson marine, they’ve suggested siliconing a through-hull to the hull (no fancy liquid bath) as a temporary measure. Apparently should work, and if it doesn’t it’s because the hull’s too thick and an in hull wouldn’t have worked anyway. Anyone done this?
11 years ago i got a jar of vaseline and carefully scooped out a wadge(technical term). I sat the wadge on the inside of the hull and pushed the transducer into it. Its been there ever since and never failed. If i ever do want to remove it i have an easy cleanup job compared to Sikaflex!
The transducer was a cheap garmin unit designed for transom mount. Why make life more difficult than it needs to be?
 

Stemar

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12 Sep 2001
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Home - Southampton, Boat - Gosport
Speaking to Hudson marine, they’ve suggested siliconing a through-hull to the hull (no fancy liquid bath) as a temporary measure. Apparently should work, and if it doesn’t it’s because the hull’s too thick and an in hull wouldn’t have worked anyway. Anyone done this?
Yes. On Jissel, the transponder was stuck to the hull with the Gosport pound shop's version of No More Nails for years. It worked fine through the best part of an inch of GRP. I understand that it might run out of puff to record deep water sooner than if fitted through the hull, but I'm far more interested in the depth when it's less than a couple of metres than when it's a couple of hundred.
 

laika

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6 Apr 2011
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A coda to this...

So transducer it probably isn't as the new one showed the same behaviour as the old one. A new job has distracted me from thinking about info vas posted but something occurred to me. From Brighton to the Hamble the depth sounder seemed to spring to life occasionally and when the water was quite deep. The second leg it was better, mostly working in >12m. After testing it with the new transducer it seemed to be occasionally working >4-5m. hmm.. What was I doing between each of these "improvements"? plugging and unplugging the the connection between the head unit and the transducer, which is a two pin connector like those digikey seatalk 3 pin ones (which obviously the ST50s also have, but not relevant here..) but a bit bigger.

In post #4 refueler said check the connections. The pins on the male side were sparkly clean and the outside of the female looked clean but what had changed was plugging and unplugging and that points distinctly to a contact thing. So I ordered some contact cleaner, unplugged, and alternated twizzling a solid wire in the female side and blasts of contact cleaner.

Just checked and I currently seem to have a (believable) 3.6m. Still don't completely trust it and I need to go out sailing to check but this could be one of those 3 page threads that was answered in the 4th post. Plus I'm £100 down with a "spare" transducer
 

vas

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laika, silly Q have you actually checked that the male pins of the connector are not only clean but as long as they should be?
I'm asking as I just spent 3-4h sorting a no gps signal on a friend's GEONAV10in old plotter. After taking the whole thing apart, looking at the back of the socket turned out that one of the 7-8pins was pushed back into the device only making contact occasionally. Obvs sod's law makes that out of ALL the pins it wasn't the 5 unused ones, but the gps antenna nmea0183 + signal...
so check clean contacts but also make sure all pins are level.
In my friends case it was a matter of a slightly bent pin that in fitting the cable in a hurry pushed it hard and pin didn't "find" the hole, but was pushed back in the socket.

V.
 

laika

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laika, silly Q have you actually checked that the male pins of the connector are not only clean but as long as they should be?
Are my male parts not only clean but as long as they should be?

That sounds like a very important question to answer and I'd hate to answer in the negative on either point.

The pins aren't noticeably bent or different sizes. I'll see how the depth reading goes this coming weekend but the contact cleaning seems to have made a difference. I don't completely trust it yet but readings were looking plausible on sunday.
 

bignick

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10 Aug 2011
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Poole
There are contacts at both ends of the Seatalk cables. have you got multiple Raymarine instruments on a Seatalk network? If so, you may need to check ALL the cables and connections. The ones at the head units, on the outside of the boat, can be even more prone to corrosion. You may have improved signal strength by cleaning the one on the back of the transducer, but the main problem may be somewhere else.
 

mattnj

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26 Jul 2007
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1,214
Had this....was head unit...not a super easy circuit/pulse to replicate (unlike speed)

I do have an st40 bidata here for sale if interested.
 
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