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The Hardware Projects

NMEA Buffer

Current GPS devices are limited in the number of devices they can interface with because their output power is limited (this is known as limited fan-out). Thus if you try to interface a plotter running on a laptop, radar, DSC radio and autopilot, your GPS might shrug and give up. A number of companies now sell buffers (aka digital amplifiers) to boost the signals and increase the fan-out. Typically, these are tens of pounds in cost but really should not be, the signals are carried on a standard RS232/RS422 serial data stream (like the serial port in a computer) for which there are a number of chips ready to be brought into action. This little project shows how a cheap but rugged NMEA Buffer can be built.

Propane/Butane Gas Alarm

You may be worried about making your own Gas Alarm and I don't want to mislead you, it is important to get it right. However, it's better to have a home constructed unit than none at all, and this project uses calibrated sensors from RS and a kit from Maplins.

Battery to battery trickle charger

The more electrical equipment we add to our boats, the bigger the battery bank has to grow. We added an extra 110 Amp-hour battery to ours and then worried about keeping it mainained but preventing it discharging if there was a fault elsewhere - a one way trickle charger. This little project is easy to construct on a tag strip and uses just a few components from Maplins

Engine Monitor System

Our Moody Eclipse only provides engine data at the internal helming station but we found we needed it in the cockpit also. We wanted engine RPM mostly, but engine temperatures, oil pressure and possibly a propane leak alarm would also be useful. The EMS is based on a PIC (Peripheral Interface Controller) which is hard wired to a number of sensors and runs a program to display the outputs on a seven segment LED display. This project is a "coming soon" 2007 project but if you are interested in sharing ideas or discussing the possibilities please get in touch.

Delayed actuator and event counter

Here is another PIC project. This one simply waits for an optical input from a lamp, counts down twenty seconds and then fires a solenoid (or relay). It then increments a counter which is displayed on a seven segment display. It has a reset button to zero the count, counts to a maximum of 99, and then shows OF for overflow, if any more events are received.

Fridge

The fridge is a complex project that should only really be tackled once you have convinced yourself you have all the necessary skills. It began when we decided to install a fridge in our Sabre 27 but did not want to pay the money for a fridge cooler unit. Since I had spent a year working on the cooling of miltary communications hardware I was well placed to design and make a fridge using cheaper technologies then the average fridge manufacturer would consider. This project uses water for removing the heat, a Peltier heat pump (you can buy these anywhere now) and a PIC as a controller. The PIC is not strictly necessary and a temperature sensor unit from Maplins would do, but the Peltier device is very hungry for current and it's therefore better to have a good controller in charge. As usual, we can provide you with a programmed PIC, although not a circuit board this time since we used standard stripboard for the prototype.

Disclaimer

We offer plans and notes on projects which we have built and used in our own boats, but we take no reponsibility and accept no liability whatsoever for the outcome of such projects constructed by you. While our projects generally require only a moderate level of skill it is important that you realise the limitations of the completed hardware, and that you thoroughly test them. This is particularly important in cases where you may come to rely on the completed projects, such as the gas sensor, NMEA buffer or fridge.

In those cases where you buy programmed PICs from us our liability is limited to replacing the PIC should there be a software/firmware fault. In all cases of supply the code is verified before it leaves us and you must ensure you are aware of the requirements of handling ESD sensitive devices. If you suspect you have blown up your PIC then talk to us, we can check it for you.

Project details

NMEA Buffer

• Description
• Circuit diagram

Gas Alarm

• Description
• Circuit diagram

Trickle Charger

• Description
• Circuit diagram