View Full Version : @ Roland (if you're from simprojects.nl) or anybody else who can help me with FFB :)

08-19-2007, 07:26 PM
Hi, I found this "Adding Force Feedback (http://www.simprojects.nl/adding_force_feedback.htm)" page on a Google search and I'd like to give it a shot myself. I have a few questions I was hoping you guys could clear up though. Here goes:
First, what sort of motors do I want? Judging from the text right in the middle of the circuit schematic (http://simprojects.nl/images/current_buffers.gif) it seems I want a 6 amp, 60 volt motor? Or does that text correspond to the ratings the diodes need? In regards to the motor, what sort of specifications am I looking for? How many horsepowers/amps/volts am I looking for?
How exactly do I tweak those resistors to fine tune? Is there some formula I'll need
What diodes and transistors do I need?Sorry for so many questions. I've never done anything along these lines before. I've done some small signal audio and audio amplifier work, but this field is new to me. Thanks in advance to anybody who can help me. :)

08-25-2007, 04:28 AM
Sorry for the delay, I already answered via email, but I paste the reply here as well in case others need this info:

Motor type depends one the amount of force you want. For my light GA flightstick, the pitch motor needs to be biggest:
I used permanent magnet DC servo motor, the lable says:
rated Torque: 50 INCH-OZ (= 0.353Nm)
Current: 20A (but I seldom use it over 5A)
Resistance: 2.8 Ohm
Induction: 5mH
Back EMF 14.8V/1000rpm
Max RPM: 4400 (that would be at 64V or so)

The Roll motor needs to be smaller as it is mounted on the pitch structure.
I used a copymachine motor, rewound with thicker wire
Probably rated about 3A / 18V

The 6A/60V in the circuit concerns the transistors. You could use complementary types that are used in audio amplifiers.
The diodes have similar rating, not critical

The * resistors form an attenuation with the 4k7 resistor. If you use two 10k resistors, the total attenuation would be about 50%.(4k7 versus 10k//10k). Lower resistors give more attenuation, so less voltage drive to the motors, so less force.
This is handy if you want less voltage for the roll than for the pitch. In my case, pitch has no resitors, (full voltage swing) and roll has two 15k resistors with the 4k7.
Take care that the motors don't overheat, as they mostly work in stalled condition. Some cooling fans may be needed to keep them OK.


08-25-2007, 05:17 AM
Hey, thanks hugely for the reply. :)
Funny, I never got your email. Didn't go in the junk mail folder either. Weird.

All that sounds pretty manageable. Any suggested transistor model numbers? It just seems like 6 amp 60 volt is pretty open in terms of eligable transistors. A quick search on mouser.com brought up this: http://www.fairchildsemi.com/ds/MJ/MJE3055T.pdf
Look suitable?

Again, thank you!

08-25-2007, 03:47 PM
Yes, the MJE3055T should be OK, with the MJE2955 as the complementary PNP type. http://www.onsemi.com/pub/Collateral/2N3055-D.PDF . Hfe looks OK too, so the driver stage should be able to handle them.
Be sure to heatsink them!


08-25-2007, 03:52 PM
Great, thanks again. I think that's it for now. I'll order some parts and give it a shot. This should be a fun project. 8-)