The purpose of the project is to be able to display the amount of chain rode that has been released when anchoring. When anchoring a boat, an anchor does not hold a boat by the weight of the anchor, rather by the flukes of an anchor digging into the bottom. If the rode (the material connecting the anchor to the boat) is not long enough then motion of the boat may pull the anchor out of the bottom. For typical conditions a chain rode should be 3-4 times the depth of the water. Markers on a chain rode are hard to see, and if using an electrical windlass to lower the anchor, the operator may be too far from the chain to see the markers. Having this digital readout is also advantageous when raising the anchor and knowing when to expect it to cross the final bow roller.
This project consists of three parts:
When on, the windlass interface outputs the current rode length at one-second intervals. The output is RS-232 (19.2k-8-n-1). The interface also receives three commands via RS-232, HOLD, CONTINUE and ZERO from the display unit. When the HOLD command is received, the interface will ignore the Up & Down lines and any changes to the hall effect sensor. This is so the windlass capstan can be used without affecting the length of the chain rode. A CONTINUE command has the interface resume normal operation of monitoring the windlass. A ZERO command will set the rode length to 000.0 feet.
display unit communicates with the interface unit which monitors extra circuitry
placed in a 900GD windlass, plus the up-down switches to the windlass relay.
The windlass interface and the windlass display communicate via rs-232.
The windlass interface typically outputs the current rode once per
second. The windlass display show
the current rode on a 4 digit LED display.
The windlass display also has a row of 4 spst momentary contact switches.
These are used to send commands to the windlass interface.
The output to the interface is RS-232 (19.2k-8-n-1).
Button one is the HOLD/CONTINUE control that will tell the windlass
interface to ignore any motion of the windlass (for such as using the capstan
rather than the gypsy). One push of
the button issues a hold command - the LED display shows "hold".
Pushing the button again issues a CONTINUE command to the windlass
interface, and the display once again shows the current rode.
The second button issues a RESET command to the windlass interface,
setting the rode to 000.0. The
third button increases the brightness of the LED's using the on board PWM. The
fourth button decreases the LED brightness.
The LEDs are updated every 5 mS, for a multiplexing rate of 20 mS. The
TMR0 timer is used in internal interrupt mode to generate the 5 mS.
Please address general comments to firstname.lastname@example.org
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