I recently installed a SR10 Pro in a new 45cc warbird. All servos are digital. I have a total of 8 servos plus 2 electric retracts, using all 10 available PWM pins. Redundancy is provided
by a M+ connected to the S.Bus In of the receiver. The M+ and the SR10 Pro are registered to the radio with different UIDs (0 and 1).
Two LiFe batteries, with their own heavy duty switch, plugged into the XT30 battery ports. Firmware is latest (2.1.6).
First of all, let me say that the SR10 Pro is the reason I updated my X10S to ACCESS. 10 PWM pins, stabilization and dual independent battery inputs make this receiver
IMMO the best receiver for large warbirds, AT LEAST ON PAPER.
However, I have discovered two issues.
1) I have a number of sensors attached to the SR10 Pro via S.Port: Airspeed sensor, Cells sensors (plugged into the balancing plug), RPM sensor.
To have all the sensors show up in the telemetry feed on the radio, I need to cycle the power on the Rx several time. It is a hit or miss: The internal sensors (RxBt, RSSI, VFR) show
up consistently. The other sensors, not always. Sometime I have to turn the switches on and off 3 to 4 times before all sensors show up.
This issue does not seem to be related to the number of external sensors hooked up. I get the same behavior even with only the airspeed sensor attached.
2) When I switch stabilization on in flight, RxBt (blue in the plot attached, scale on the left) shows a significant voltage drop,
from 6.6V typical of charged LiFes, down to 6.2 to 6.3V. Interestingly, the Cells sensors only report a rather smaller drop (about 50 mV, green and red) at the battery.
In the attached telemetry plot, the time when the stab is on is circled in red. Note that with the stab off, Cells and RxBt show basically identical readings.
Also (not shown) the drop is worse at higher speed. It is possible the plane develops oscillations, though not large enough to be noticed when flying without stabilization.
It makes sense for the stabilizer to work the servos harder, with higher currents flowing out of the battery. However, the rather small drop at the battery suggests
that the currents involved is probably a few amps at the most. So why is the RxBt dropping so much? I am inclined to think that the drop does not occur between the battery and the Rx (the lines are short, and the switches are heavy duty type, bought from a reputable vendor), but
rather is due to the circuit that separates the batteries. This separation can be achieved in two ways: a conventional diode or an ideal diode. A conventional diode will introduce a voltage drop when
forward biased. The drop seems to be consistent with a Schottky diode. An ideal diode, on the other hand, does not introduce a significant drop, but requires more circuitry.
For example, on the RB-20, the board shows to nice MOSFETs indicating that ideal diodes are used to achieve separation.
At this moment, I have not measured to actual current out of the batteries, so these are just hunches.
I really do not need the stabilizer on this warbird, but I think that the second issue should be discussed. It is a significant voltage drop. I use LiFes, but there are still lots of people out there who use NiCad, and
in this case, the drop would affect at least how servos respond. Also, the drop means that power is dissipated in the Rx. That could cause issues too.
The first issue is, however, annoying. Maybe I just got a bad Rx (bought it from Aloft).
Would be interested to know if other people out there had similar experiences.
by a M+ connected to the S.Bus In of the receiver. The M+ and the SR10 Pro are registered to the radio with different UIDs (0 and 1).
Two LiFe batteries, with their own heavy duty switch, plugged into the XT30 battery ports. Firmware is latest (2.1.6).
First of all, let me say that the SR10 Pro is the reason I updated my X10S to ACCESS. 10 PWM pins, stabilization and dual independent battery inputs make this receiver
IMMO the best receiver for large warbirds, AT LEAST ON PAPER.
However, I have discovered two issues.
1) I have a number of sensors attached to the SR10 Pro via S.Port: Airspeed sensor, Cells sensors (plugged into the balancing plug), RPM sensor.
To have all the sensors show up in the telemetry feed on the radio, I need to cycle the power on the Rx several time. It is a hit or miss: The internal sensors (RxBt, RSSI, VFR) show
up consistently. The other sensors, not always. Sometime I have to turn the switches on and off 3 to 4 times before all sensors show up.
This issue does not seem to be related to the number of external sensors hooked up. I get the same behavior even with only the airspeed sensor attached.
2) When I switch stabilization on in flight, RxBt (blue in the plot attached, scale on the left) shows a significant voltage drop,
from 6.6V typical of charged LiFes, down to 6.2 to 6.3V. Interestingly, the Cells sensors only report a rather smaller drop (about 50 mV, green and red) at the battery.
In the attached telemetry plot, the time when the stab is on is circled in red. Note that with the stab off, Cells and RxBt show basically identical readings.
Also (not shown) the drop is worse at higher speed. It is possible the plane develops oscillations, though not large enough to be noticed when flying without stabilization.
It makes sense for the stabilizer to work the servos harder, with higher currents flowing out of the battery. However, the rather small drop at the battery suggests
that the currents involved is probably a few amps at the most. So why is the RxBt dropping so much? I am inclined to think that the drop does not occur between the battery and the Rx (the lines are short, and the switches are heavy duty type, bought from a reputable vendor), but
rather is due to the circuit that separates the batteries. This separation can be achieved in two ways: a conventional diode or an ideal diode. A conventional diode will introduce a voltage drop when
forward biased. The drop seems to be consistent with a Schottky diode. An ideal diode, on the other hand, does not introduce a significant drop, but requires more circuitry.
For example, on the RB-20, the board shows to nice MOSFETs indicating that ideal diodes are used to achieve separation.
At this moment, I have not measured to actual current out of the batteries, so these are just hunches.
I really do not need the stabilizer on this warbird, but I think that the second issue should be discussed. It is a significant voltage drop. I use LiFes, but there are still lots of people out there who use NiCad, and
in this case, the drop would affect at least how servos respond. Also, the drop means that power is dissipated in the Rx. That could cause issues too.
The first issue is, however, annoying. Maybe I just got a bad Rx (bought it from Aloft).
Would be interested to know if other people out there had similar experiences.
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