Sunday, December 30, 2012

HotSpot using an iPad

While gathering up (purchasing the required items) for my ipad, to add to the boat,  I came across this piece of information from Latitude 38 Magazine. (They have an on line version as well as a PDF version of their published magazine.)
It is a story about using your iPad as a hotspot for up to five other devices. Hop over to their story and get the full text.  I haven't purchased my iPad yet and was unaware of this feature. But I certainly hope to use it.

Any way, Latitude 38 goes on to  state, "Just go to the main TelCel office, replace your U.S. SIM card with a Mexican SIM card, and your iPad becomes a 'hot spot' — meaning that up to five other nearby devices can wirelessly use it for internet access also."

Of course this all depends on whether your carrier supports it. For instance, in the USA,  Verizon includes the hot-spot feature with the iPad data plans, while AT&T doesn't support it.

This has distinct advantages for us, because we carry a PC, a Mac, and soon to be added, an iPad. We use to use a cell phone modem that could connect up to five devices also. I liked it a lot because we never had to plug it into a computer to get a connection. We had two, from two different carriers because of the different reception coverage areas.

But I was also thinking about the iMux I bought. It can only connect one device at a time. And so I was wondering if I can connect with the iPad to the iMux when underway, and  stream the data to other devices, such as my PC which also has charting software?? I will write a blog later in 2013 about how I set up my iMux, iPad, and iNavX. Till then, those with an iPad can follow these instructions for setup.

Follow this link to get the low down of how to set up your Hotspot 
or follow this
                                               Tap Settings > General > Cellular Data:

Tap Personal Hotspot and turn it on:

After configuring Personal Hotspot, you can directly access the settings from Settings > Personal Hotspot.

Friday, December 28, 2012

Beginners Guide to Raymarine's Seatalk and Derivatives

Seatalk is Raymarine's proprietary communication "language" for interconnecting Raymarine instruments. Unfortunately Raymarine keeps the technical details of Seatalk secret and so the nitty critty of the system often has to be reversed engineered if designing something to work with Ray's different seatalk buses. However, most of you out there just want a plug and play system and I can say that Raymarine has done a pretty good job of that.

Raymarine has produced four communications protocols featuring SeaTalk as the root of the protocol's name. These include:
  • SeaTalk (also referred to as SeaTalk1 or first generation SeaTalk)
  • SeaTalk2
  • SeaTalkng
  • SeaTalkhs

Seatalk to nmea0183 and RS232

Seatalk is the same as seatalk1. Ray just added the 1 after developing other more modern buses that they called seatalk2, seatalk hs and seatalk ng. Seatalk1 is ray's propriety version of nmea 0183. Seatalk1 is readily able to be converted to nmea 0183. Raymarine supply an accessory (Part #E85001) for converting Seatalk to NMEA 0183. Also, ShipModul's and Brookhouse's MUXes also convert Seatalk to NMEA 0183. Alternatively, if you have the ST60 repeater, you will find a NMEA output on the device which can connect directly to a SOB COM port.

Seatalk which is often referred to now, as seatalk1, is a multi-talker, multi-listener approach using serial data at low data rates (4.8Kbps). Compare that to nmea 0183 which is predominately a single talker, multi listener unless one uses a multiplexer.

The network used proprietary cables and connectors that were designed for the marine environment. The connectors are three pin molded and incorporate 1/8” automotive spades as mating elements. 

Seatalk cable
The network could be implemented as either a simple daisy chain structure or the more robust approaches of backbone, spur or star design.

SeaTalk uses three wires, connected in parallel to all devices on the bus:
  1.  +12V    Supply, red
  2.  GND    Supply, grey
  3.  Data     Serial Data, yellow
There is no master on the bus. Every device has equal rights and is allowed to talk as soon as it recognizes the bus to be idle (+12V for at least 10/4800 seconds). Low priority messages use a longer or randomly selected idle-bus-waiting-time. This allows messages from other devices with a higher priority to be transmitted first. The different waiting times of all devices make data collisions (two or more devices start talking at exactly the same moment) very rare.

Unlike the Seatalk2 and Seatalk ng communications protocols, Seatalk communications protocol does not feature termination. Any Seatalk instruments and instruments or autopilot components featuring a 1st generation Seatalk interface which does not have a Seatalk ng interface (ex. ST40/60+ Instrument Displays, ST6001, etc.) can be interfaced to one another, in any order, using standard Seatalk cable. Seatalk cables can be joined using a Seatalk Junction Block, splices, marine grade terminal strips, or R55006 Seatalk Auxiliary Junction Boxes. This method of interfacing is referred to as a Seatalk bus. The Seatalk bus will typically be powered via a Seatalk Auxiliary Junction Box or via a Seatalk power cable which has been connected to one of the Seatalk devices.

Seatalk hs is raymarines high speed version of ethernet. It is plug and play.

By using SeaTalk hs networking, you can instantly transfer radar, chartplotter, fishfinder, thermal imaging and navigation functions. Configuring your system is a simple as determining which SeaTalk hs devices you'd like to have (chart, radar, sonar, video) and where you would like to see them.
The most basic system may consist of a C Series Widescreen or an E Series Widescreen with a DSM30, DSM300 or a radar. The components are all auto sensing, there is no complicated setup required. Simply plug them in.

E series integrates nmea 0183, 2000 and seatalk hs
Raymarine E-Series can input/output data via good old NMEA 0183, Seatalk (Ray’s proprietary improvement on 0183), Seatalk2 (sort of NMEA 2000 but seatalk ng is the bus that mimic's nmea 2000), and Seatalk HS (actually Ethernet).  Plus the E’s (and C’s) do something called data bridging where they take data from one bus and put it onto another bus.

Raymarine has network switches when working between 3 to 8 devices. They are.......
  1. The new HS-5 Seatalk hs Network Switch which has five ports
  2. Seatalk hs Network Switch which has 8 ports.

The following devices have Seatalk hs connections and can be easily connected together via the Seatalk hs network switch and Seatalk hs network cables:

  1. New e Series Multifunction Displays
  2. New c Series Multifunction Displays
  3. C Series Widescreen Multifunction Display
  4. E Series Widescreen Multifunction Displays
  5. G Series Navigation
  6. E Series Classic legacy Display 
  7. T Series Thermal Cameras
  8. DSM30 and DSM300 Fishfinders
  9. Super HD and HD Digital Open Array Radar
  10. Digital Radome Radar

Seatalk 2
Seatalk 2 is a five conductor system that has some N2K functionality. This network does require terminators at each end.

Seatalk 2 network 
and here is the comparison of the different network cables below.....
seatalk1 cable

 Provided you do not want to connect to NMEA2000, you can connect a Seatalkng system to Seatalk(1) using a suitable Seatalkng bridging product (such as an ST70 instrument) and adapter cables to connect the two systems.
If you intend doing this, note that:
You can connect a single Seatalk(1) network to Seatalkng using an adapter cable and one bridging product (e.g. ST70 instrument).
You can connect two separate Seatalk(1) networks to SeaTalkng using different adapter cables and bridging products (e.g. ST70 instruments), but the two Seatalk(1) networks must NOT be connected together. See below for the diagrams
Seatalk2 cable

Seatalk 2 whilst is not plug compatible with NMEA2000 or SeatalkNG, adapter cables are available. Raymarine A06048 is the part number for seatalk ng to seatalk2 adapter cable. (not shown).
Any data available on the SeaTalk2 network will then be available on the SeaTalk NG network. Only one connection is needed per network.
This adapter enables an existing instrument network, using the SeaTalk2 5-pin connectors, to interface with a SeaTalk NG network.
*Note that this cable cannot be used to connect a SeatalkNG network to the Seatalk2 port on the back of a Raymarine E-Series display. Use cable A06061 for that purpose.

Older Style of Seatalk hs cable

Raymarine’s current generation of ethernet cables replaces the RJ45 connector (seen to the left) with a waterproof vibration tolerant twist pin connector that is designed for the marine environment.
The new RayNet (F) to RayNet (F) network cable can be used to daisy-chain 2 adjacent RayNet devices together. It is also useful for joining two adjacent HS-5 Network Switches together on larger systems where multiple switches are necessary.

Rayamrine has a number of adapter cables which most are to adapt the older RJ45 with the newer Raynet cable. They can be seen here

An NMEA standard for the transfer of NMEA 2000 messages using an Ethernet protocol is being developed that will be called OneNet.

Correct method seatalk1 to seatalk ng via ST70 instrument
No ST70 for bridge
Do not link different seatalk1 networks together.
Seatalk ng

SeaTalkng is an interconnection bus for Raymarine products, and comprises a main
backbone to which Raymarine products are connected via spur cables.
Seatalk ng is basically NMEA 2000 and can be connected to a NMEA 2000 network via an adapter cable.
SeaTalkng comprises a single backbone terminated with two terminators, one at each end. Spur cables connect the backbone to individual Seatalkng products.
Small diameter cable connectors are used throughout the system, to make installation easier. Cables and connectors are color-coded to reduce the likelihood of misconnection.
A wide range of different cable lengths provides flexibility and obviates the need for cutting and splicing cables.
Three-way, five-way and in-line connection pieces are available to connect cables, to
deploy Seatalkng as required.

Typical seatalk ng network,

One of the things I like with the raymarine seatalk ng is the 5 way connector blocks. Something I wish NMEA 2000 would have. NMEA 2000 also has this and be seen here.
Plan the route of the Seatalk ng backbone so that it runs as close as is practicable to the intended location of each Seatalk ng product, to keep spur lengths to a minimum.
Products connect to the backbone via spur cables. Spurs connect to the backbone via either a Seatalk ng T-Piece or a Seatalkng 5-Way Connector

Seatalk (sic) has a number of adapter cables, of which one is the seatalk ng to NMEA 2000 adapter cable. Part number A06045 for the female cable and A06046 for the male cable.
You can see a range from rayamrine, of the adapter cables here.

Raymarine with Wifi and Bluetooth
This is still in it's infancy, but is now working. It can only get better from here. There iOS app has been released and can be viewed here. I wonder if it will work with an iMux instead of their e-series display WiFi?

RayControl transforms your tablet into a full function Raymarine MFD. Remotely control and view electronic charting, sonar, radar, and even thermal night vision, right from your tablet.

RayControl emulates Raymarine MFD’s with touch screen interaction and a virtual slide out MFD keyboard. The slide out virtual keyboard gives you control of all MFD functions and the virtual uni-controller allows you rotate through menus and adjustments effortlessly.

Take a look....

Perhaps in the not to distant future an iMux will no longer be required as manufacturers integrate wifi and bluetooth into their products. I look forward to that, but in the mean time, the cheapest option for someone who has already invested heavily in existing technology is a Wifi seatalk/nmea multiplexer.
Whether you use Navionics or iNavX on your iPad, you have to get the various Seatalk output data from your instruments, GPS, AIS into a format that can be understood by either of those programs. That is exactly what you have to do to get the same information into an onboard computer. Typically, this is accomplished by a multiplexer which is spliced into the Seatalk network. Most of the data comes at a slow baud rate, but the data from an AIS is at a much faster rate. The multiplexer takes all of these data streams and sorts them out and sends them in a controlled output to the computer or if WiFi capable, to your iThing. But now, with MFD's having WiFi integrated, it takes the hassle out of setting up a WiFi multiplexer. Also, it is one less device to purchase, to get WiFi   Looking at the video, RayControl also has some high bandwidth data displayed on your iThing. I'm impressed, and wonder what the other big manufacturers will bring to the market.
One last question. Does the new WiFi enabled e-series display integrate with iNavX for the data? I'm not expecting the chart to come across, but basic nmea 0183 sentences. Perhaps a reader will let us know.

Tuesday, December 25, 2012

Replaceing Sanitation Hose

Some of you may have experienced the "smelly" boat syndrome, and a lot of the time this often points to the sanitation hose which is permeating the smell, from the contents inside the hose.

Analysis and Design
When sanitation system odors end up on the wrong side of the hoses and tanks that are designed to contain them, the most frequent analysis is, “they are permeated” and a lot of the experts call for wholesale hose replacement. In fact, while this may ultimately be necessary, it’s often a case of addressing the symptom rather than the cause. If the hoses are replaced and the design is flawed, then it’s likely the new hoses will, once again, fail or permeate prematurely. (see avoiding sanitation woes)

How do you test for permeated hose? Once you have eliminated all other sources for the odour, take a flannel and soak it in hot water. Ring it out and drape over the suspect hose for a few minutes. Then take the flannel and place in a zip lock bag and take outside to fresh air. Open the zip lock bag and smell. If you smell sewage, then you hose is permeated.

Before I begin with my solution(s), I just want to recap some of the salient points for a healthy head/holding tank systems and things you should look at on your boats sanitation system. By ensuring these procedures and implementing the points below on design layout, they can greatly reduce the the permeated hose problem.

  • Rinse the holding tank out before layup and after every pump out. Lots of H2O helps with cleaning the remainder of the "solids" which tend to fall to the bottom of the tank and build up.
  • If the holding tank has an inspection port, use that to wash down the sides of the tank; but watch for splatter back!!
  • What sort of tank should I have? I prefer polyethylene tanks. The holding tank in many boats is constructed of low density polyethylene, heat welded from flat sheet with polyethylene fittings. Not much can go wrong as polyethylene does not corrode, is impervious to odour and has great impact resistance. Fiberglass would be my second choice. Metal tanks are a poor choice due to corrosion.
  • Next step is to check the other components, Y valve,  macerator pump, hoses, hose clamps, tightness of joints, and vent line. Two outlets can prevent the need for a Y valve.
  • Flow into the tank from the head should be on top of the tank This will depend on your location of the tank, but if attached to the side, slosh from a boat heeling can back flow down the delivery hose and becomes the standing waste inside the hose. It also allows you to disconnect the hoses from the fittings if the tank is near full
  • The air vent should also be at the top of the tank and as large as practicably possible. Better still, put two vent hoses on to allow for a cross flow of air inside the tank. Aerobic bugs don't make the stink. Anaerobic bugs are responsible for the sewer smell.
  • The discharge line should also come from the top of the tank with a drop pipe. It is a poor design when the discharge is from a fitting at the bottom, or lower side of the tank and this leads to the hoses continuously submerged in effluent.
  • All hoses should run "down hill" or free draining to prevent standing effluent. When hoses are installed with large dips, low spots, or "u" shaped bends, effluent will settle in those bends, and it will be a challenge for even the best permeation resistant sanitation hose. These low spots can also lead to clogging.
This is all in an ideal world where holding tanks are designed properly, made from the correct material, plumbed correctly and the sanitation hose is the best money can buy. It doesn't happen. For instance, the holding tank location is often decided by what space is available. This often leads to hoses being plumbed that have residual effluent sitting in the hose. Sewage allowed to sit in the hose develops acids and gas that shorten its odor-free life. This is especially the case with white vinyl extra heavy-duty sanitation hose. Good installations are short and self- draining (no kinks, loops, or dips), with tight connections. Overtight fittings and clamping can damage hose ends, causing leaks and odorsOn my boat, the tank is higher than my head and the toilet has to pump up hill to the holding tank. Without extra flushing, this leads to effluent sitting in the hose. This also true of my discharge line.

To the left is a quick drawing of my head and the associated items in the sanitation circuit. There are a number of problems with my system.

  1. From the Macerator pump, it pumps up hill to the tank and if not flushed sufficiently, effluent stays in the line.
  2. The intake to the holding tank is on the side and should be on the top
  3. The outflow from the tank is from the bottom and therefore effluent will sit in the hose from the outlet to the Diaphragm Pump. A better option would be to have the outlet from the top of the holding tank with a drop pipe inside to the bottom for pick up 
So because of these poor designs in my sanitation system, effluent eventually permeates the sanitation hose and the boat becomes smelly. We all know how hard (and messy) it can be to change that sanitation hose and I have two ideas which may help with that. In addition, next time I'm at the boat, I will be changing the intake on the side of the holding tank, to the top of the tank.
First is to use barrel connectors made for alkathene (MDPE) pipe at each end of the sanitation hose. I use Hansen fittings. They may be called something different in your part of the world, but are commonly found in the farming industry and the marine industry. Our local chandler has sold these for years, but I never knew about the barrel fitting until I visited a more extensive store dedicated to Hanson fittings.

Barrel connector = big Nut
The picture to the left shows a barrel connector, which is the big nut in the middle. With one of these at each end and the sanitation hose between, one simply undoes the nut and pull the whole hose out to replace it.

Barrel nut  in the picture to the right undone. The big nut turns and slides back to allow the male end to slide out side ways.

Barrel nut in picture to the left showing the "O" ring which sits across the face of the opposite side for sealing.

Hanson makes hose tails, but I prefer to make my own.  They are good for tight/short runs of hose, Take a 1 and 1/4 inch nipple and turn one end down to 38mm. It just takes the threads off and I find the hose is a better fit and easier to get on and off. One and a half inch sanitation hose fits really good with a hose clip. One can also use the Hanson threaded end to pipe fitting (male straight coupling), by unscrewing the locking nut and discarding it, and slide the sanitation hose on and secure with hose clamps. If using Akathene pipe as suggested below, then you slide the pipe onto the tail and screw the nut over the pipe which cinches it down onto the tail of the fitting.
An image of one is shown below.

The other idea, of which I'm going to try out, is to use Alkathene (MDPE) pipe. This is a flexible pipe made from Polyethylene and I'll be using a medium density pipe. I'm trying it out because there is no info or data of anyone ever using this type of hose for boat sanitation hose. And yet it makes sense to me.This material is the same stuff that holding tanks are made from, and is used for effluent in our cities main sewer system and used by farmers for effluent discharge. While the stuff I will be using is designed for the transport of water, it is made from the same stuff the effluent MDPE pipe is, but at a size I can use. i.e. One and a half inches and one inch. (25 and 38mm)
Be aware that the pipe comes in low density and ranges through several levels to high density. It also comes in a range of sizes. The 40mm pipe and fittings are the one and a half inch  variety and in fact the inside of the pipe (ID) and  outside of the tails measure 38mm. This is the "real" size.

I'm setting this up so that, if I'm not happy with the Alkathene pipe, I can revert back to the sanitation hose without much ado. But I'm confident it will stop the permeation woes. The MDPE pipe is not as flexible as sanitation hose and if working with tight bends, you may have to use a Hanson elbow to get it around a corner. It is however, flexible , resistant to cracking, corrosion resistant  (some sanitation hose has a metal coil within the walls),chemical and abrasion resistant, excellent pressure resistance, easy to install, and more flexible than HDPE pipe. I have also used it around my farm, and it is so easy to connect, a child could do it.

While I would like the discharge line from the holding tank to come from the top of the tank, I'm going to leave it for the time being at the bottom of the tank. I'm hoping that by using MDPE pipe, which should be as good as any holding tank made from PE, then the issue of effluent in the line will not be a problem.

I also acknowledge that if you are using sanitation hose with barrel connectors each end, that they then in turn have to be connected to your devices. If your devices don't have a screw in fitting (like most PE holding tanks do),and has hose tails only, then one is faced with extra hose and hose clamps at each end. I think this is worth the extra "risk", and if the hose tail off the barrel connector is kept close to (<1/8 inch) from your device hose tail, then permeation at those points would be minimal.

Another change which I will also be doing is to put a barrel nut either side of the macerator pump, so that it is easy to take out should I need to work on it. It's in a tight location at the moment and difficult to get at the pump. These barrel nuts will make taking out the pump so much easier. I already have one on the discharge side of the macerator pump with a non return valve ( a joker valve, by which I machined  the barrel coupling to take), and a shut off valve so that if taking the pump out, I don't get a back flow from the hose leading up to the intake of the holding tank.

Below are some photo's showing the ease of the barrel nut disconnect, using both sanitation hose (in white) and Alkathene (MDPE) pipe in black.

You can place the nut of the barrel nut so that either stays on the removed hose section, or stays at the appliance fitting end.

Hope this will help for your next change of your sanitation hose. Below are some links that I thought might help.

A comparison of Trident Sanitation hose.
Need a custom made holding tank. In our city one of the plastic tank manufacturers will make custom tanks on any shape you give them. It seems Raritan also does this. Check out your local area; there may be someone who makes PE tanks.

Tuesday, December 4, 2012

Beginners guide to Nmea 2000, Nmea 0183, and bridging

Most of the new instruments for boats are now coming out with NMEA 2000 (National Marine Electronics Association) as the preferred method of connecting various devices on a boat. The NMEA 2000 transmits data through Controller Area Network (CAN bus). It simplifies the connection and shares information among different devices by using a single trunk cable. Compared with NMEA 0183 in “RS422” interface, NMEA 2000 has better transmission reliability and shares data easily in a network. 
Here's a good primer for constructing NMEA 2000 networks
And Power and Motor Yacht has an article worth reading; " A Breakdown of Protocol: How a Boats' System Converse"
 I'll attempt here to explain some of the data networks and how to connect various different types.

Typical Nmea 2000 Backbone.

The Nmea 2000 Backbone is pretty easy to set up as you can see from the diagram. All you need is the right parts/cables/terminators and follow some simple rules. Read the link above for the do's and don't's. Even hooking in a new device is relatively easy. More hooking up Legacy Equipment to this network later. But here is some tables that illustrate the differences between the old and new nmea standards.

Nmea 2000 verses Nmea 0183

Nmea 0183
Nmea 0183 and it's various versions is the older standard from NMEA. But it will be around for quite a bit longer.
NMEA 0183 is a low-cost, low-capacity, single-transmitter/multi-receiver network for
interconnecting marine electronic devices, also known as a “single talker/multiple
listener” interface. The NMEA 0183 Standard, along with RS-232, RS-422, etc., is often called “Asynchronous Serial” interfaces. This means that data is transmitted serially (bit-by-bit) on a single line. Furthermore, the transmission is asynchronous because no “clock” signal is transmitted with the data.

Single Talker, Multiple Listener

Multi Talker to Single Listener

There are multiple versions of the NMEA 0183 specification in use in the marine industry.  Prior to NMEA 0183 version 2.0, including NMEA 0180 and NMEA 0182, the hardware employed a single ended interface implemented with one signal wire and a common ground. Early versions of the NMEA 0183 Standard specified that “listeners” must be isolated from ship’s ground but allowed ”talkers” to be simple single-ended drivers (referenced to ground). Furthermore, the input impedance of a listener was specified to be greater than 500 ohms, and opto-isolation was recommended. Later versions of the Standard retained the opto-isolated listener recommendation, but revised the talker requirement to be RS-422 compliant. As a result, there exist some instruments (talkers) with single-ended outputs and others with RS-422 (differential) outputs.
All implementations from 2.0 and later employ a differential interface with two signal wires.

Due to the difference between the single ended and differential interfaces 
implemented, older versions of NMEA 0183 prior to 
version 2.0 cannot be connected to equipment supporting NMEA 0183 version 2.0 or higher without proper interface circuitry. Do not connect one of the signal wires of the differential interface to the common ground of the single ended interface!  
Single-ended drivers are perhaps the simplest to design. The desired state indicated by the presence or absence of a voltage above some threshold. For NMEA 0183 (ver. 1.5), a “one” was any voltage less than +0.5, while a ‘zero’ was any voltage greater than +4.0. Besides their design simplicity, single ended drivers need only one wire to transmit data. Since voltages are referenced to Ground, no signal return line is needed.
Interconnecting NMEA instruments can be a real hassle if one is not familiar with the different types of connections. The NMEA-0183 standard specifies the talker ports (outputs) and listener ports (inputs) to be differential. This means that the data is transported by means of voltage levels over two wires, separated from ground. Roughly, the voltage levels swing between 0 and 5 Volt, and both wires are in opposite phase. When one is at 5V, the other is 0V and vice versa
Some  manufacturer's though, would not adhere to the standard. It would have been perfect if you could simply connect the 'A' terminal on a talker to the 'A terminal of a listener and do the same with the 'B' terminal. So what came about were these "single ended" connections which complicated matters for the DYI person.
There are four types of connections possible with differential and single ended.
They are,

  • Differential > Differential
  • Single ended > Single ended
  • Single ended > Differential
  • Differential > Single ended
What distinguishes NMEA 0183, RS-232, and RS-422 from each other is their physical voltage and current interface levels. NMEA 0183 originally allowed “single-ended” drive, but was later updated to differential drive (RS-422).  RS-232 is a bipolar interface and RS-422 is differential drive. These are explained in more detail next.

RS232 data is bi-polar. +3 TO +12 volts indicates an "ON or 0-state (SPACE) condition" while A -3 to -12 volts indicates an "OFF" 1-state (MARK) condition. Modern computer equipment ignores the negative level and accepts a zero voltage level as the "OFF" state. In fact, the "ON" state may be achieved with lesser positive potential. This means circuits powered by 5 VDC are capable of driving RS232 circuits directly, however, the overall range that the RS232 signal may be transmitted/received may be dramatically reduced. RS-232 interfaces are somewhat sensitive to environmental noise (motors, ignition pulses, etc.) and are therefore usually limited to installations of tens of feet or less.

RS-422 is most commonly called “differential drive”. Two wires, A and B are used for this interface, but neither wire is grounded. A “zero” is produced by making A positive with respect to B and a “one” by making B positive with respect to A. It is therefore the direction of current flow rather than a voltage level that determines the logic state. It is important to note that neither RS-422 signal line (A and B) can be connected to Ground.

RS-232 interfaces are somewhat sensitive to environmental noise (motors, ignition pulses, etc.) and are therefore usually limited to installations of tens of feet or less.
RS422 standard that is widely used for the transmission of high speed serial data. Transmissions using RS-232 are limited in their speed and the length over which data can be transferred. Normally the maximum is 19.2 k baud and the distance 15 metres, although for slow transmission speeds longer lengths can sometimes be used.
It is very immune to external noise, and so can be used over greater distances (hundreds of feet).Under the latest version of NMEA 0183, all talkers are supposed to be RS-422. RS-422 is not strictly compatible with RS-232, but most RS-422 drivers will act like a single-ended driver if only one output line is used. In this way, the RS-422 “A” output can be used to drive either an RS-232 input directly. The “B” line is simply left unconnected.
Fortunately, both types of outputs will drive opto-isolated listeners. What is "optp-isolation"... Opto-isolators are actually quite simple devices. They consist of a light source (LED) coupled to a photo transistor.  The input data signal turns the LED on and off which causes the photo transistor to switch on and off. The LED and photo transistor are completely isolated from each other electrically. The data source (talker) must provide sufficient current and voltage to power the LED. A current limiting resistor in series with the LED is generally used for protection.  The advantage of opto-isolated inputs is that virtually any type of driver can activate them.

Here are the possible connections...
Differential to Differential
Single ended to Single Ended
Single ended to Differential
Differential to Single ended
When multiple listeners of different nature (single-ended vs. differential) are to be connected to a talker port, the same connection rules apply. Here, two differential and one single-ended listener are connected to the differential output of a multiplexer.

Multiple Talker Circuits.

Where a single listener requires data from multiple talkers, a data multiplexer or combiner will need to be installed.  Data multiplexers buffer the input sentences from each talker, and provide a single data stream that may then be connected to multiple listeners.
There are a number of companies that provide multiplexers and these days, you can even get a multiplexer that outputs Nmea 0183 Sentences via Wifi.

There is a practical limit to the number of talkers that can be combined based on the available bandwidth and the number of sentences that each talker transmits.  Products are available that combine up to four talkers and replicate the combined output into four or more new talker circuits, each capable of supporting multiple listeners.   Here you see a typical setup using a Brookhouse multiplexer which has also the capability of converting Seatalk to Nmea as well.

Typical Multiple Talkers Combined to Single Listener
But what do we do if we want to mix our older hardware which runs on the older "bus" of Nmea 0183 and the newer Nmea 2000?
Well, I can only find two devices that do this directly. Presented here are......
Here's some of what the company says... 
The Actisense® NMEA 2000 to NMEA 0183 Gateway is the easiest way to link between a boats old and new data networks. The NGW-1 can convert NMEA 0183 data into NMEA 2000 data and vice-versa.

The NGW-1 allows current NMEA 0183 equipment to be kept, or allows the latest NMEA 2000 equipment to be incorporated into the NMEA 0183 system. Once the single cable NMEA 2000 bus system has been installed, data from any node on the bus can be listened to by any other, including any NMEA 0183 instruments connected using an NGW-1.

The NMEA 2000 network acts like a bi-directional multiplexer, allowing all data sources to talk and listen to each other.

At the moment, this seems the simplest way of achieving a bi directional talking of the two Nmea standards.

Amec NK-80

An alternative to Actisense would be this product from Amec
NK-80 is a gateway between NMEA 0183 electronics devices and NMEA 2000 device/network. NK-80 allows users to connect NMEA 2000 network with their existing NMEA 0183 devices. 

Key Features of NK-80 according to the company: 

‧Upgrade NMEA 0183 equipment to NMEA 2000 
‧Conversion between NMEA 2000 and NMEA 0183 
‧Full NMEA 2000 compliance 
‧Full NMEA 0183 compliance 
‧Compact size, easy for installation 
‧Isolation between NMEA 0183 and NMEA 2000 
‧Fully galvanically isolated for electrical spike protection

One final way that may prove beneficial to some. There are now devices such as MFD's that have both NMEA 2000 and NMEA 0183 in and out. It may seem odd that the Raymarine E-Series can input/output data via good old NMEA 0183, SeaTalk, (similiar to NMEA 0183) SeaTalk2 (actually NMEA 2000), and SeaTalk HS (actually Ethernet).  So the E’s (and C’s) do something called data bridging. It works by taking data, if it is not on a particular level, and converts and sends the data on at the higher level. I suspect it is converted up to the higher level, but not converted down. Perhaps someone can leave a comment and advise as to whether this is true?

That's it for now. Hopefully soon, I'll post about Raymarine and their Seatalk interface, along with it's interface with NMEA2000 and NMEA0183

Monday, November 19, 2012

Spar Hitch

The Spar Hitch is the second knot I teach my guests when they come and stay on the boat. Of course, the first knot everyone learns is the bowline. The Spar Hitch also goes by other names and among them is the Ground Line Hitch. Check out also the Millers Hitch and the Constrictor Knot. They all do the same job really. And I only teach a clove hitch in passing now. I think the Spar Hitch is just as easy and more secure.

The knot starts out like a clove hitch. One turn around the spar and over the standing end and back over the spar. You can do this either to the left or the right.

Take the bitter end and pass under the spar and over the first completed turn. (A clove hitch here would go under that first completed turn.)
Then take the bitter end and pass it under the start of the first turn.

Finally take both the standing end and bitter end and snug the knot tight. The knot can be made for quick release by placing a loop in the bitter end before placing under the start of the standing end.
I use this for securing items to railing or life lines. Even fenders secured this way on small life lines will not slip. Quick, easy and secure.

Finally, below are some variations of this hitch.

Monday, November 12, 2012


Shortly after writing about my Paddle Wheel Dilemma, Mark Corke also wrote about the Cruzpro (also mentioned in my blog) and offered up some pro's and con's. Go over to Mark's blog and have a read. He is going to buy one and install it. Keep an eye on his blog site for updates and reports of this interesting device.

Thursday, November 1, 2012

Paddle Wheel Transducer Dilemma

A lot of you out there will know of the frustration when your paddle wheel gets clogged, and fails to work. Pulling the thing out (if it is a thru-hull) to clean is not only a chore, but can let in a bit of sea water.
I have an Airmar DST800 (Depth, Speed, Temperature)  which I bought around 2005. It was for Raymarine ST60 instruments and did the job fairly well. When removing the transducer, I get an ingress of water because it does not have a self closing  valve which would close as the transducer is removed. I believe (I have been told, correctly or incorrectly) this is still the case for the Raymarine  DST800; and yet most of the other transducers of this model (post 2005) have the self closing valve. See their brochure here for the DST800. I was told the transducers were changed after 2005  so that they have the self closing valve, BUT not the Raymarine version. A little research was required.

My instuments (ST60 Tridata) work by taking an analog signal input from the transducer. My ST60 will only display seatalk input if changed to a repeater display. It will not display nmea 0183 or 2000 data, UNLESS one can convert that data back to seatalk (1)

My choices after some contemplation were
 1. Stay as I am
 2. Change to a new DST800  with nmea 0183 output,  and get a nmea 0183 to Raymarine
 converter so I can have the self closing valve.
 3. Purchase a new DST900-EM which has no paddle wheel and picks up speed by electromagnetic induction, also with a self closing valve

Considering those choices, here are the problems.

  1. There are plenty of multiplexers out there that will convert Seatalk to nmea 0183; but I've yet to find one that converts nmea 0183 to Seatalk. This conversion would not be needed if the new DST800 has BOTH a self closing valve and analog output. The brochure here says it only comes in nmea 0183 & 2000 outputs.
  2. After contacting an Airmar dealer through email, the DST900 isn't on the market as yet. Here's what he said.(Oct. 2012) "The DST900 is still not available yet from Airmar. No date or cost on the release." AND (as the brochure reads only nmea 2000) I would then have to change nmea 2000 to nmea 0183 and then to Seatalk or analog signal. Can't be done, I think. More about that later. I made some more enquiries.
Notwithstanding that statement, I'm sure they will be released soon and have included here a little of what Airmar has to say about the product. For those with nmea 2000, a great choice when it is released!
Here's Airmar's blurb. Check their Brochure here.

Airmar’s NEW DST900-EM is the industries first all-in-one depth, speed, and temperature sensor with no moving parts. The NEW innovative speed sensor circuitry creates a magnetic field in the water. Speed is accurately measured by the voltage created through 

conductive properties of water, combined with the forward motion of a vessel. With no moving parts, the DST900-EM is capable of accurate readings at all vessel speeds. What sets the DST900-EM apart from the traditional speed paddlewheel is the excellent 

accuracy at very low-speeds between 0.5 and 5 knots (0.6 and 6 MPH)—an important feature for sailboat racing. The DST900-EM’s accuracy at high-speeds up to 50 knots (57 MPH) makes it an important sensor for powerboats. By eliminating the traditional paddlewheel, there is no fouling, and drag is reduced to a minimum of 6.3 mm (0.25”) below the hull due to the low-profile housing.  
Rated at 100 W power, the 235 kHz depth transducer provides depth readings in as little as 0.45 m (1.4’) of water and can reach depths up to 180 m (600’). The narrow-beam of this transducer will 
deliver accurate depth readings at speeds over 35 knots (40 MPH). 
Additionally, the 235 kHz frequency prevents mutual interference with other echosounders on the vessel. 
The DST900-EM’s fast-response water temperature sensor provides ±0.2°C (±0.1°F) of accuracy to help in finding the optimum conditions for fishing or swimming. Airmar’s patented housing design incorporates the popular self-closing valve. When the transducer is removed for cleaning, the valve minimizes water flow 
into the boat. 
The lightning-fast processor inside the DST900-EM makes calculations every second, so it can respond quickly to changes in speed, depth, and temperature. This data is then sent to the NMEA 2000®network via a single devicenet cable for an easy plug-and-play installation.

Sounds like it will just support nmea 2000,

But recent enquires put a different light on the question of legacy formats. A recent email had this to say...  "The DST900 most likely will have the self closing valve. The DST900 will be capable of outputting Analog, NMEA 0183 and NMEA 2000 so it should cover all your needs including working with the ST60.
At this point we still do not know when it will be released." 
So if I wait long enough, maybe this will be my solution of choice. Sometimes this is called vapor ware.

So, I'm no closer to solving the paddle wheel "blues". However....

Here's another solution. Don't have a transducer at all!!
This solution by Cruzpro here is great if you don't mind SOG instead of STW .

The CruzPro SOG1 takes NMEA 0183 data from a GPS and creates an analog paddlewheel signal so you can display Speed Over the Ground (SOG) on a standard speed log without a transducer.

SOG1 NMEA 0183 to paddlewheel signal converter

The SOG1 creates an analog paddlewheel output signal from a GPS NMEA 0183 $GPRMC sentence so you can display Speed Over the Ground (SOG) on a standard analog or digital speed log.
The SOG1 replaces a thru-hull or transom mount paddlewheel speed transducer and provides Speed Over the Ground in place of Speed Through the Water.
No more cleaning of paddlewheels to remove marine growth or weeds.
Provides a more accurate estimate of time to get to your destination since it is not affected by water currents and provides a resolution of 0.01 knots from 0.00 to 60.00 knots.
The SOG1 is powered by 12VDC and draws less than 0.020 amps.

Back to to Airmar's current selection; Thinking that the new DST800(V) isn't available for Raymarine instruments, I came across the following info in this Newsletter. It appears that perhaps they do have a new DST800 that will do the ST60 instruments AND the self closing valve. Read below their blurb....

The DST800 Retractable TRIDUCER® Multisensor is now available with
The industry’s only depth, speed and temperature retractable transducer is
now available with a valve! The DST800V meets customer demand for our
patented valve assembly that prevents water from rushing into the hull when
the insert is removed. And the addition of a valve lets boaters service the new
DST800V while the vessel is in the water, saving time and money!
Offered in NMEA 2000®, NMEA 0183 or Analog versions, the new DST800V simplifies any
installation by delivering three readings while having only one hole drilled in the bottom of the
boat. These three important readings can then be displayed on instruments, echosounders,
NMEA repeaters or Network navigation systems.
The new DST800V includes:
• Airmar’s patented self-closing valve assembly.
• Two O-rings, one at the top and one at the bottom for a water-tight seal.
• Industry standard 2” thru-hull hole size.
• NMEA 2000®, NMEA 0183 or Analog versions available.
Although the new DST800V contains Airmar's popular TRIDUCER® insert, the original DST800inserts cannot be retrofitted into the new housing with a valve. This is because all DST800 insertsmanufactured prior to November 2005 have ribs and an alignment key. If an older style insert withribs is pushed into the new P617 housing (which contains a valve), the insert will damage thevalve assembly.
However, all DST800s manufactured after November 2005, do not have ribs or an alignment keyon the insert. These can be retrofitted into existing installations that have a plastic P17, bronzeB17 or stainless steel SS577 housing. To insure proper sealing when installing a DST800 in aP17, B17 or SS577 housing, the yellow O-ring at the top must be replaced with a black O-ring.

Sooooo; my choices now are, I can wait for the NO paddle wheel DST900 and change out (choosing the analog version). Change to the upgraded DST800 (with self closing valve) but have to pull it out occasionally to clean the paddle wheel ( but not suffer the ingress of water due to a self closing valve), or go no transducer and loose the depth and water temperature in the process. Hmmmm, I think I will just sit and wait another year!
What would you do?