The Tripmate is designed to operate on 6 volts DC. You can run it off 4 AA batteries that mount inside it's case, but I hate batteries. Delorme does offer an adapter for the Tripmate that plugs into your automobile power point, and will convert 12v to 6v for the GPS ($40.00), I however am cheap too.
Though designed to operate at 6 volts, after some testing, I have found that the Tripmate is perfectly happy with 5 volts. You could build a 6 volt supply from an adjustable regulator, but as the 5V is so easily available and a single part, why deal with PC board and more parts?
Acquire a 7805 voltage regulator, some very small gauge (28 or 24) hookup wire, and some Heat Shrink Tube to insulate your wire connections. (All available at Radio Shack).
There is PLENTY of room inside the Tripmate to mount the regulator. You could mount it on a small piece of PC board or metal and lay it inside the case, or drill a hole and mount it to the metal case separation shield after removing the 3 mounting screws.
If you mount it on the separation shield, as I did, drill 2 holes, one for a mounting screw to hold the regulator in place, and another larger hole to pass through 3 small wires to make connections to the GPS. Be careful of the placement of the regulator on the shield, look at the picture, look at the main GPS board, imagine the wires coming through and where they need to go. Mine did fit just fine, "In the right place".
Please look at the blister pack that your regulator came in (or a data book) to confirm your exact regulator's pin outs. Be sure before proceeding.
The large metal mounting tab and the center leg on the regulator are common, and ground. Solder a wire to the center pin of the regulator, and solder this wire to an edge of the metal case of the main GPS unit. The shield case cover does not screw down directly to the main GPS shield case and therefore does not provide a good electrical connection. The cover will provide a good heat sink for the regulator, but add this wire from the regulator to ensure a good ground to the main GPS case.
We will now route the power coming into the GPS through the regulator. The YELLOW wire in the feeder cable (from PIN 9 of the DB9 computer connector ) is POWER INTO the GPS. Disconnect this yellow wire from the GPS Board, and connect it to the INPUT leg of the regulator (you will need to add a bit of wire to extend it, shrink tube the splice joint and the regulator leg).
Connect a wire to the OUTPUT leg of the regulator (shrink tube here). This wire will feed the GPS 5 volts. We will also feed this 5 volts to the DTR input of the GPS so it will turn on when power is applied. The DTR line is a way of remotely turning the Tripmate ON and OFF (5 volts on the line ON, 0 volts OFF).
If you look at the battery pack power connection socket on the GPS main board, you will see three pins. The pin closest to the edge of the board is ground. The pin toward the main body of the GPS board is Positive. The pin in the center connects to the solder pad on the GPS board where we removed the Yellow power input wire. Power fed into the GPS via the DB9 connector really goes nowhere but to this center pin. You can not connect the output of the regulator to where the yellow wire was on the GPS board. Follow the circuit trace on the GPS board from the POSITIVE pin in the socket, about a quarter of an inch away on the trace you will see a small round pin sticking up through the GPS board. You can confirm this if you wish by doing a continuity check with an ohm meter. From the POSITIVE pin of the power socket to your new found round pin should be 0 ohms. This pin makes a convenient place to make our power connections.
We will connect the output of the regulator here, and supply power from here to the DTR.
The DTR input connection comes from the DB9 computer connector pin 4 via the RED wire to the GPS main board. Cut the RED wire, but leave enough to jumper over to the round power pin. Insulate the free end of the wire with some shrink wrap. As we will be feeding the DTR 5 volts from the regulator, there is no need for a resistor as mentioned in some other modification descriptions you may have seen.
Connect (solder) the red jumper wire from the DTR input and the wire from the OUTPUT of the regulator to the round pin.
Check it over twice... Make sure you have insulated all splices, the free end of the red wire, and both outer legs of the regulator.
Button it up.... your done.
As for the Connector wiring:
I also purchased a DB9 MALE connector and a Shielded hood for it. Plus a 6' car power cord with a cigarette lighter plug on one end and bare wires on the other (Radio Shack again...)
Power (12 volts) to Pin 9, Ground to Pin 5.
Jumper Pins 2 and 3 together (so the ASTRAL command loops back into the GPS to self-initialize it). These jumpered pins are also where you pick off the GPS data to go to your TNC. "Out of the Box" the Tripmate expects to be connected to a laptop with the Street Atlas Program running. One of the first things the Tripmate does when it is powered up, is send a "ASTRAL" string out it's serial line (who knows what that stands for) to the laptop. The Street Atlas software simply sends an "ASTRAL" back to the Tripmate. They are sort of saying "I'm here, and I'm here Too.... Lets GO". Shorting the RX and TX lines on the connector together (Pins 2 and 3), routes the Tripmate startup "ASTRAL" right back to itself so it thinks that the laptop and software is running.... and away it goes.
I also picked off the 12 volts and ran it to the TNC and HT, one power source for the whole Tracker system.
Tripmate DB9 connector pin outs:
73 and good luck, N9UUR
(11-29-98)
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