The GST-1 normally derives its power from the computer serial port. Some
devices do not have the control signals available from which the GST-1
derives its power while other devices, switch the control signal power off
and on at various rates or simply do not supply sufficient power for the
This FAQ discusses the problems involved and their solutions.
In the case of devices which switch the RS-232 control lines off and on,
normal operation of the Earthmate is interrupted every time the line
switches. This forces the Earthmate to restart every time. The result is
that the Earthmate will never acquire enough satellites for a position
Devices which do not supply the RS-232 control signals can not power the
GST-1 and thus the Earthmate will never turn on.
There a couple of different solutions to the above problems:
The GST-1 may be powered with a 9V battery connected between pin 5
(Negative) and Pin 6 (Positive) on
the GST-1 female computer connector.
Do not ever apply 9 volts to pin 9 of the GST-1 or directly to any pin
on your Earthmate. To do so
will probably destroy your Earthmate.
DeLorme offers an external power adapter for the Earthmate. All
GST-1's currently being shipped are
capable of receiving power from the DeLorme power adapter, as well as
from a serial port.
The following information is provided without warranty of any kind. To the
best of our knowledge it is correct but it is your responsibility To
verify the information. We can not accept any liability for the
consequences of the use of this information.
For those of you interested in building your own Earthmate external power
adapter, you can do so quite reasonably.
Simply put, the Earthmate Power adapter supplies +6 Volts to pin 9 on the
Earthmate connector with pin 5 being ground.
A simple male to female DB-9 connector with pins 2, 3, 4, and 5 wired
across Between the male and female sides provides the signal paths for all
required Earthmate signals. Providing +6V to pin 9 of the (male DB-9)
The negative side of the supply connects to pin 5.
The required 6V can be derived from 12V by using a 6 Volt 3 terminal
regulator such as the LM7806 or similar
device. DO NOT USE a LM78L06 as it can not handle the power.
Return to the main GST-1 page.
* Earthmate is a trademark of DeLorme.