User manual

56
Receiver power supply
Auxiliary function
Y-lead,
Order No. 3936.11
PRX stabilised
receiver power supply,
Order No. 4136
For reasons of safety, do not use battery boxes or dry
cell batteries.
The voltage of the on-board power supply will be dis-
played at the bottom right of the transmitter’s screen
while the model is in operation:
#01
2:22h
Stp
Flt
0:00
0:00
5.5V
3.9V
M
HoTT
If the voltage falls below the warning thresh-
old – 3.80 V as standard – set in the “RX SERVO
TEST” display of the “SETUP, DISPLAYS” sub-menu
of the »Telemetry« menu, page 248, then the sys-
tem generates a visual and audible low voltage warn-
ing.
Despite this feature, be sure to check the condi-
tion of the battery at regular intervals. Do not wait
for the warning to be issued before recharging
the battery.
Note:
An overview of available batteries, chargers and
current source test instruments can be found in
the Graupner RC main catalog or in Internet at
www.graupner.de. A selection of suitable Computer
chargers are listed in the table on page 16.
500 mAh for every digital servo.
For example, from this point of view a battery with
1400 mAh would be the absolute minimum to power
a receiver system with a total of 4 analog servos. But
be sure to also consider the receiver itself into the
calculation because its bidirectional functionality will
draw about 70 mA of current too.
Connect the power supply preferably by way of the
socket/s which are close to connectors of attached
servos. Where only high-power servos are connected,
it may be necessary to use all receiver battery con-
nections. Even where only two batteries are used via
1 PRX it is preferable to use the receiver connections
closest to the servos which draw the most current.
The figure below shows an example of a stabilized
receiver power supply (PRX-5A, order no. 4136) for
the connection of two batteries. As an alternative
solution, a switch could be inserted with power sup-
ply cables to two receiver connectors. Such a double
connection not only reduces the risks associated with
a cable break but also ensures a more uniform supply
of power to attached servos.
If a separate battery is connected to each receiver
battery connection, be absolutely sure the batteries
have the same voltage and power rating. Never con-
nect different battery types or batteries charged to
significantly different levels to the receiver. This can
lead to effects similar to short circuit conditions. In
such cases, insert voltage stabilizers, such as the
PRX-5A receiver power supply, between the batteries
and the receiver.
Auxiliary function
Y-lead,
Order No. 3936.11
PRX stabilised
receiver power supply,
Order No. 4136
Among other aspects, the safe operation of a model
depends on a reliable power supply. In the event that,
despite smooth operating rods, fully charged battery,
battery leads with adequate cross-section, minimum
contact resistances at connectors, etc., the transmit-
ter indicates repeated receiver voltage collapses or
is receiver voltage is generally too low; please give
attention to the following notices:
Give primary attention to fully charged batteries when
model operation is to be started. Be sure that the
contact surfaces of connectors and switches really
are low resistance. If necessary, measure the voltage
drop across installed switch cables when they are
under load because even new heavy-duty switches
can cause a voltage drop of up to 0.2 V. This value
can increase in contacts by factors as a consequence
of aging and oxidation. The constant vibrations and
jarring also takes its toll on contacts to produce a
creeping increase of contact resistance.
Servos present another possible problem source.
Even rather small servos like a Graupner/JR DS-281
can draw up to 0.75 A of current when it is blocks un-
der load. Just four of these servos in a “foam” model
can therefore load down the on-board power supply
by as much as 3 A …
A further factor is that 2.4 GHz receivers generally
pass control signals to servos at a higher rate than
with comparable receivers used in earlier frequency
ranges. This equates to shorter “off” periods, which
also has an effect on the power consumption of the
receiving system. The current drain of many of today’s
digital servos is also higher, reflected by their greatly
improved ability to hold the prescribed position be-
tween control signals.
Therefore you should choose a power supply which
will not break down under greater loads but rather
always deliver sufficient voltage. To “calculate” nec-
essary battery capacity you should always figure on
at least 350 mAh for every analog servo and at least
Receiver power supply