GyPSI™ & RapidFix™ GPS Interfacing Beacons

Frequently Asked Questions

 

Q. How do I download position data from my GPS to my beacon?

A. You must have an NMEA 0183 output ready GPS unit and a GPS interface cable. The NMEA 0183 optical interface connector supplied with your ACR beacon must be connected to the GPS interface cable using the wiring diagram information supplied by ACR and the GPS unit manufacturer. Turn on your GPS unit and allow it to acquire the necessary satellites. Make sure the output is set to NMEA 0183 with the GGA sentence configured if necessary. Connect the NMEA 0183 interface cable to the GPS unit and the ACR beacon. The ACR beacon "wakes up" every few seconds. As soon as it detects the presence of a valid data source it will initiate a data down load.

Q. How long does it take to down load position coordinates from my GPS to my beacon?

A. Upon connection with a properly operating and fully acquired GPS unit, the ACR beacon will take less than four minutes to synchronize and download coordinates. Subsequent coordinate updates occur every 20 minutes. These subsequent position updates will take from a few seconds to no more than 20 seconds to complete. If the interface cable is disconnected you may need to wait for up to four minutes for the GPS and the beacon data interchange to synchronize again.

Q. How does the GPS data get from my GPS to the beacon?

A. The GPS unit transmits data as electrical energy through the GPS interface cable to the ACR optical interfacing connector. The ACR optical interfacing connector has an infrared LED and sensor located in it. The electrical energy supplied by the GPS unit is converted to infrared light in the ACR optical interfacing plug. Data from the GPS unit is transmitted via infrared light to the beacon through the translucent beacon top cap or lens when the ACR optical interface plug is properly engaged. The beacon has an infrared detector that decodes the light pulses. ACR uses an optical interface design to eliminate the potential for leaks and corrosion common to mechanically interfacing devices.

Q. How can I test my beacon to see if it has acquired GPS data?

A. Lift the switch to the test position, making sure not to break the tab. If the beacon has acquired GPS data there will be a beep and LED flash within 4 seconds after the self-test has completed.

Q. Does my GPS unit have to be set up in a special way to transmit position coordinates via the NMEA 0183 interface?

A. For the GPS to transmit data make sure the NMEA 0183 output is turned on and the GGA NMEA sentence is selected or turned on. Consult your GPS user’s manual for information on configuring the NMEA output.

Q. Does my beacon need any special set up to accept GPS data?

A. You do not have to do anything special to the beacon. If it is hooked to a valid data source, that has been properly set up to deliver NMEA format with the GGA sentence, it will automatically attempt to download the data and form an emergency message that includes the position data. If disconnected it will automatically dump the position data after 4 hours and revert to a default emergency message.

Q. What is the maximum length my GPS cable can be?

A. ACR Electronics recommends a maximum length of 400 feet using 24 AWG wire. Contact your GPS owner’s manual for more detailed information.

Q. What happens if I plug the GPS into the beacon first, without waiting for it to acquire satellites?

A. The beacon will function normally, but will not store GPS coordinates. The beacon will continue to look for satellites and as soon as the GPS has acquired satellites the data will be transferred to the beacon.

Q. How long does the beacon hold data in memory?

A. The beacon retains GPS data until one of the following conditions happens:

The battery is disconnected.

The beacon is placed in the on mode and then returned to the off position.

Q. How much power is needed to run the IR LED on the GPS cable?

A. The minimum power needed is 3.3VDC and 2mA.

Q. What if I already have other devices hooked up to my NMEA 0183 output cable, can I still splice my RapidFix™ GPS cable to the NMEA 0183 output cable?

A. YES – As long as you have enough current to supply 2mA to the beacon. Most GPS are capable of supporting multiple devices on the NMEA interface.