After reading on FSforce forum that one of the best force feedback sticks for Flightsimulator is the Microsoft Sidewinder Forcefeedback-2 stick, I decided to see if it was possible to hack this stick's hardware in similar way as I had done with Logitech Wingman Force Feedback 3D joystick
It turned out that it is quite doable, and it is actually easier to boost
the stick's motor current compared to the Logitech Wingman stick.
Below is a description how to hack the Microsoft Sidewinder Forcefeedback-2
stick and modify for higher current.
Warning: This stick internals contains high
voltages when connected to mains voltage.
Bought on eBay for €50,-
Bottom side, and with bottom removed.
(The special screws need to be slowly turned to remove)
Remove AC/DC board. then disconnect all connectors from main PCB and unscrew
main PCB
In order to trace the other electronics, I also removed the boards in the
handle.
The middle picture shows the sensor that checks for presence of your hand on
the stick. It is an IR LED and receiver. When IR signal is seen by receiver,
the FF power section is switched off. The IR light is blocked when your hand
is on the stick, and then power section is activated.
After removing all boards, I hooked everything up separately on my desk to
do some testing.
The AC/DC supply delivers 24Vdc to the main PCB. The CPU receives the USB
signals, checks the position of the X, Y, rudder and Throttle potmeters,
12-switches, and controls the motor current.
The motor current control and power stages are all discrete. Motor current
is around +/-0.7A max, with 8.5 ohm motors.
This stick's hardware is actually quite well done: The circuits really
control the current through the motors instead of just adjusting the PWM
duty-cycle. Therefore, the motor current is precisely controlled, and not
dependent on the motor internal resistance. This architecture also makes it
easier to boost the current with exact ratio.
Below some hi-res pictures of the main PCB electronics. Looks a bit
daunting, but for the hack we only need to modify a small part.
Below is the schematic of one channel. It is an H-bridge with P-MOSFETs
and N-MOSFETs.
(each HAT3004R contains a P/N MOSFET pair)
The drive has push-pull stages for each MOSFET and one transistor that can
switch-on both P- and N-MOSFETs together. (Note the crossed H-bridge
connection, so no short will occur)
In this type of drive with all MOSFETs switching, shoot-through (conduction
from 24V - GND via 2 MOSFETs) can easily occur if there is a small delay in
one of the MOSFET drives. The designer has therefore chosen to have only one
side of the bridge active at the time for one motor current direction, the
other side will be fully switched off, and the inductive current will flow
through the other side MOSFET's body diodes. Drawback of this method is that
the power dissipation in the non-active MOSFET's is actually quite high, due
to the higher voltage drop across the body diodes.
You can also see that there are current sense resistors in each side of
the bridge. The voltages across the current sense resistors are processed
with OPAMPs and serve as the feedback of the force current loop.
By reducing the current sense resistors R7 ~ R9, the system will increase
the voltage across the motors to keep the same feedback voltage, thus the
current through the motors will increase.
So 2x higher motor current, decrease the current sense resistors to half
their original value.
But the higher current will increase the power dissipation in the MOSFETs.
Above 1.4A, MOSFETs get really hot. I wanted to increase current 4x, which
required using better MOSFETs and adding external Schottky diodes. I also
improved the supply filtering, to avoid noise coupling into sensitive
circuits.
Motor considerations: When current increases, the voltage drop across the
motors will also increase.
The original motors in this FF stick have 8.5 ohm resistance. you could
probably increase the current up to 1.4A and still keep the same motors. But
at higher currents, the voltage drop across the motors will be too high, and
switching duty-cycle goes to 100%, for which this system was not designed.
Also the original motors become quite hot) . In this design, the supply
voltage must be kept at around 24V for all circuits to operate normally. So
when choosing motors, best to choose a type that has ~ 12V drop at max
current.
Note on DC supply: The original AC/DC 24V supply is quite weak, it cannot deliver much more than the power for original drive. So for higher motor currents, you have to use a 24V supply that can deliver more current.
Description of the Hack:
Below is the modified circuit diagram.
* I soldered 3 more 1R resistors on each 1R current sense resistor.
* I changed the MOSFETs from HAT3004R to Vishay Si4532CD MOSFETs which have
similar gate drive characteristics, but lower Rdson
* I added an NXP PMEG3050EP 30V/5A Schottky diode across each MOSFET to
reduce the power dissipation in the MOSFETs
* I added 1 ceramic filter capacitor next to main supply electrolytic
capacitor, and added two ceramic decoupling capacitors at reserved
positions on the board.
Adding the Schottky diodes is a bit tricky, only 4 can be added on the
top side, the other 4 have to be mounted on bottom side, and this requires
some cutting in the bottom ground plane.
Below pictures show he details of the modifications.
Note: C10 and C56 don't seem to have have a connection to ground. It is
recommended to add this connection by adding a wire to ground as shown in
yellow. (thanks to Steve Payne for noticing this)
The final result after modification looks like below:
Other circuits of the Microsoft Sidewinder Forcefeedback-2 stick :
As I wanted to use the hacked board in my Force Feedback Yoke II , I had
re-wired the above circuits on a separate board, see below pictures.
I kept the IR sensor link intact, as it can be used during testing to
switch-on/off the motor drive.
For the 24V supply, I used a 24V / 3.5A power supply "brick".
Update 2022/01/23:
Big thanks to Steve Payne who had traced the MS Sidewinder FFB2 PCB
electronics, please see the drawings below.
This new hacked FF electronics has been build into my
Force feedback yoke
II construction.
For the force feedback software link to FS2004, I have used FSForce, which is a great improvement over the standard force feedback from FS2004. No more delays, more realistic elevator trimming, and extremely tweak-able settings for many different effects.
For more info on the mechanical build, see Force Feedback Yoke II page.