The EDS unit has a power jack for use with
an external power source. The EDS-EPS
(External Power Supply) unit (purchased
separately) was specifically designed to
provide the necessary voltage regulation,
filtering and protection from aircraft power,
see figures below. If the EDS unit will be
operating in very cold temperatures where
battery failure may be likely, a battery
connector can be wired up to use an external
9 volt battery placed somewhere warmer. It
can also be used as an emergency backup,
electronically replacing the internal battery
with the external battery that is plugged in
the external jack.
Female Jack (EDS unit)
Outer (nut) = neg (-)
Inner (pin) = pos (+)
Male plug
Outer ring = neg (-)
Inner tip = pos (+)
CAUTION
Diode shunt for reverse polarity
protection is provided internally
IN
OUT
Top view of EDS unit
The EDS-EPS (External Power Supply) input jack and plug.
EDS-EPS
EDS
unit
10 - 26 VDC
input strip
The EDS-EPS with internal noise and glitch filter unit can
operate up to six EDS units.
External
Battery
EDS
unit
If you wish to provide a voltage source other than a 9 volt battery it
must be a clean and steady voltage between 7.0 and 10.0 volts DC
with no more that 50 mv. P. P. of ripple or noise from 0.025 Hz to
2.5 KHz. The schematic and parts list below is that of the EDS-
EPS unit and can be used as a design example. The LM317
precision programmable voltage regulator must be electrically
insulated yet firmly mounted to a metal surface for an adequate heat-
sink to dissipate heat from about 750 mw. of the electrical
equivalence of heat.
Part ref
Part description
C1, C6
10.0 ufd/15 VDC Tant.
C2, C4, C5
0.1 ufd/50 mono.
R1
1.275 K Ohm 1%
R2
220 Ohm 1%
D1
1N4001
T1, T2
MH-T250 (supplied by Mtn. High E&S Co.)
VR1
LM317 precision programmable voltage regulator.
Providing External Power to the EDS unit
