5. Once the bind process is complete and before power is cycled on the receiver, remove the
bind plug and store it in a convenient place. Failure to remove the bind plug will result in
the receiver going back into bind mode.
Note:
The only time it is necessary to do a rebind is if different failsafe positions are desired
e.g., servo travel has been reversed after the initial bind, or if the receiver is to be
bound to a different model memory.
Failsafe
Failsafe positions are also set during binding. In the unlikely event that the radio link is lost
during use, the receiver will drive the servos to their preprogrammed failsafe positions (normally
full brakes and straight steering). If the receiver is turned on prior to turning on the transmitter,
the receiver will enter failsafe mode, driving the servos to their preset failsafe positions. When
the transmitter is turned on, normal control is resumed.
Tips on Using Spektrum 2.4GHz
Your DSM equipped 2.4GHz system is intuitive to operate, functioning nearly identically to FM
systems. Following are a few common questions from customers.
1. Q: Which do I turn on first, the transmitter or the receiver?
A: It doesn’t matter, although it is suggested to turn the transmitter on first. If the receiver is
turned on first, all channels will be driven to the failsafe position set during binding. When the
transmitter is then turned on, the transmitter scans the 2.4GHz band and acquires an open
channel. Then the receiver that was previously bound to the transmitter scans the band and
finds the GUID (Globally Unique Identifier code) stored during binding. The system then connects
and operates normally. If the transmitter is turned on first, the transmitter scans the 2.4GHz
band and acquires an open channel. When the receiver is turned on, the receiver scans the
2.4GHz band looking for the previously stored GUID. When it locates the specific GUID code and
confirms uncorrupted repeatable packet information, the system connects and normal operation
takes place. Typically this takes 2 to 6 seconds.
2. Q: Sometimes the system takes longer to connect and sometimes it doesn’t connect
at all?
A: In order for the system to connect (after the receiver is bound) the receiver must receive
a large number of consecutive uninterrupted perfect packets from the transmitter in order to
connect. This process is purposely critical of the environment ensuring that it’s safe to drive or
fly when the system does connect. If the transmitter is too close to the receiver (less that 4 ft.)
or if the transmitter is located near metal objects (metal TX case, the bed of a truck, the top of
a metal work bench, etc.) connection will take longer and in some cases connection will not
occur as the system is receiving reflected 2.4GHz energy from itself and is interpreting this as
unfriendly noise. Moving the system away from metal objects or moving the transmitter away
from the receiver and powering the system again will cause a connection to occur. This only
happens during the initial connection. Once connected the system is locked in and should a loss
of signal occur (failsafe) the system connects immediately (4ms) when signal is regained.
3. Q: I’ve heard that the DSM system is less tolerant of low voltage. Is that correct?
A: All DSM receivers have an operational voltage range of 3.5 to 9.6 volts. With most systems
this is not a problem as in fact most servos cease to operate at around 3.8 volts. When using
multiple high-current draw servos with a single or inadequate battery/power source, heavy
momentary loads can cause the voltage to dip below this 3.5-volt threshold thus causing the
entire system (servos and receiver) to brown out. When the voltage drops below the low voltage
threshold (3.5 volts), the DSM receiver must reboot (go through the startup process of scanning
the band and finding the transmitter) and this can take several seconds. Please read the receiver
power requirement section as this explains how to test for and prevent this occurrence.
SR3520 Instruction Manual
Spektrum’s SR3520 3-channel DSM2
™
Micro Race receiver is compatible with Spektrum DSM2
surface transmitters and operates in DSM2 mode.
Specifications:
Type: DSM2
Channels: 3
Band: 2.4GHz
Dimensions (LxWxH): 1.0 x 0.8 x 0.5 in (26 x 21 x 12mm)
Weight: .1 oz (4 g)
Voltage Range: 3.5–9.6V
Note:
If using a DX3R and 5.5ms frame rate is selected, only two channels (steering and
throttle) are operational.
Binding Receiver to Transmitter
In order to operate, the receiver must be bound to the transmitter. Binding is the process of
teaching the receiver the specific transmitter’s code called GUID (Globally Unique Identifier).
When a receiver is bound to a transmitter/model memory, the receiver will only respond to that
specific transmitter/model memory.
Binding
Note:
The SR3520 receiver utilizes the DSM2 protocol and is only compatible with DSM2
surface transmitters such as the DX3R.
1. With the receiver off, insert the bind plug into the BIND port in the receiver.
2. Power the receiver through any port. If an ESC is being used, power on the ESC with the
ESC lead plugged in the throttle channel port. The orange LED will flash continuously
indicating that the receiver is in bind mode.
3. With the steering wheel, throttle trigger and Aux channel (if applicable) in the desired preset
failsafe positions, initiate the bind process with your Spektrum transmitter which will also
store the failsafe positions. Please see the next section for more information about Failsafe.
4. The LED on the receiver should now be solid, indicating a successful bind has taken place.
4. Q: Sometimes my receiver loses its bind and won’t connect, requiring rebinding. What
happens if the bind is lost during use?
A: The receiver will never lose its bind unless it’s instructed to. It’s important to understand that
during the binding process the receiver not only learns the GUID (code) of the transmitter but the
transmitter learns and stores the type of receiver that it’s bound to.
If the system fails to connect, more than likely the transmitter is near conductive material
(transmitter case, truck bed, etc.) and the reflected 2.4GHz energy is preventing the system from
connecting. (See #2 above)
Powering the receiver with a separate
receiver pack
Powering the receiver with an ESC
Bind Plug
LED
