Force Feedback

[Rickertsen2]

Originally Posted by Andrew Blair

Okay, so use a capacitor to store the charge while you wait in autonomous, then use it during drive.Maybe only have it kick in in big collisions/current drops/whatever.

Exactly! A capacitor and a diode to prevent backflow could be used. You would probably need to limit the inrush to the capacitor when it is first plugged in as well.

[Andrew Blair]

Alright then! One or two capacitor setups, wired into a motor controller, to the motors. This is looking pretty complicated. Maybe thats why nobody seems to have done it..........

[Cuog]

There are 4 5VDC out pins I'm pretty sure that through programming you can control these. (correct me if im wrong but with some hard thinking it can be done)

For the feedback you would hack apart one of the old black joysticks FIRST used to give us. and add one of the 3 volt radioshack hobby motors connected with a thickish ruberband to some orst of pulley that will pull or push your joystick where the feedback is telling it to, and BOOM you have a forced feedback controller that you can still overpower.

[Andrew Blair]

Originally Posted by Cuog

There are 4 5VDC out pins I'm pretty sure that through programming you can control these. (correct me if im wrong but with some hard thinking it can be done)

For the feedback you would hack apart one of the old black joysticks FIRST used to give us. and add one of the 3 volt radioshack hobby motors connected with a thickish ruberband to some orst of pulley that will pull or push your joystick where the feedback is telling it to, and BOOM you have a forced feedback controller that you can still overpower.

Exactly what I was thinking. Where'd you get that sheet? I can't read it easily from the post. Lego stuff would actually work great for this.

[Rickertsen2]

Originally Posted by Andrew Blair

Exactly what I was thinking. Where'd you get that sheet? I can't read it easily from the post. Lego stuff would actually work great for this.

I was thinking of hacking an off the shelf force feedback joystick.

That pinout posted above is for a generic gameport. The joystick ports on the OI are slightly different. On ports 1&3 pins 5,8,9,15 are outputs designed for driving small LEDs. on ports 2&4 they are inputs for buttons. The diagram posted above shows these as being +5v which is incorrect for the OI. It is possible to configure these pins to output a voltage on ports 1&3, but they are current limited to 10ma each. That only gets you 80ma in addition to whatever small amount of power is available on pin 1 (5v). A standard lego motor draws a stall current of 300ma @ 5v according to http://www.philohome.com/motors/motorcomp.htm.

[Cuog]

i found it just by googleing "gameport pinout" and it was like in the first 5,

Rickertsen2, thanks for pointing out the slight differences in the RC and computer joysticks i think that could have really messed something up

[Cuog]

The joystick ports on the OI are slightly different. On ports 1&3 pins 5,8,9,15 are outputs designed for driving small LEDs. on ports 2&4 they are inputs for buttons. The diagram posted above shows these as being +5v which is incorrect for the OI. It is possible to configure these pins to output a voltage on ports 1&3, but they are current limited to 10ma each. That only gets you 80ma in addition to whatever small amount of power is available on pin 1 (5v). A standard lego motor draws a stall current of 300ma @ 5v according to http://www.philohome.com/motors/motorcomp.htm.

How do you control the pins via programming?


Yes, I've been intriuged now I must build it,
Cuog

[Rickertsen2]

Originally Posted by Cuog

How do you control the pins via programming?


Yes, I've been intriuged now I must build it,
Cuog

you use the variables :
Pwm1_green
Pwm1_red
Pwm2_green
Pwm2_red
Relay1_red
Relay1_green
Relay2_red
Relay2_green

Which pins these correspond to are listed in the IO reference guide. They are defined in ifi_aliases.h. To use them for something you must override their default behavior which is set up in user_routines.c. Unfortunately these variables are also control the lights on the OI itself, so if you use them for something else, you will no longer have the use of those lights for debug purposes.

[Andrew Blair]

Rickertsen, the hack would be much easier, I must agree. And if the current isn't there, it'll just be sub par. But thats alright, it'll still be give feed back probably.

[Cuog]

Thanks, I have been learning the FIRST specific code and i just didnt know what commands controlled the pins

[DonRotolo]

Originally Posted by Andrew Blair

I'm wondering if you can get power from the joystick outputs/inputs. It would seem to me that you could run a small, albeit small motor off 9 volts, 1.5 amps. Actually, thats quite a bit of power, if we could get to it. If I remember correctly you can run LEDs from them. Correct me if I'm wrong please!

According to IFI "The current limit of the +5V Aux from all 4 ports is about 100mA. The Aux Fault Led will start illumination when the current draw from the +5V Aux Outputs total about 120 mA and the +5V Aux voltage will have dropped to about 4.5 volts. Worse case, short condition: after about 30 seconds, the voltage will be at about 300 mV with a current of about 250 mA."

Now, I don't know if that means 100 mA from each port, or 100 mA from all four combined.

Don

[Andrew Blair]

How does storing current on a capacitor work? I know that the voltage out will not exceed the voltage in (ex: 5 volt cap. with 2.5 volts applied will charge to 2.5 volts), but how does current charge?

[Al Skierkiewicz]

Originally Posted by Andrew Blair

How does storing current on a capacitor work? I know that the voltage out will not exceed the voltage in (ex: 5 volt cap. with 2.5 volts applied will charge to 2.5 volts), but how does current charge?

Capacitors store energy by building up a charge between two plates. The larger the value of the cap the more charge is stored. However, it is not an infinite amount nor anything approaching the charge stored in a battery or that delivered by the OI power supply. The LED outputs on the OI are current limited internally to prevent the OI from handling large amounts of current. In addition the OI +5 volt rail that feeds these outputs is derived from a three terminal regulator that is also current limited and temperature sensitive. IFI had to make some choices in the design and size was one of those. To give us high current, +5 volt outputs, would have required significant design changes and would have resulted in a much larger package. Until electrical rules will allow an external power supply and interface for the OI we will be limited in what we can do at the operator station. Remember, the OI & RC are about as bullet proof as they can be. They take a beating and keep on ticking when they are used as designed.

[Alan Anderson]

Originally Posted by Al Skierkiewicz

Until electrical rules will allow an external power supply and interface for the OI we will be limited in what we can do at the operator station.

So you're still safely within the box too, Al?

Come on, people, take off your blinders! The rules do let us connect externally-powered portable computing devices to the OI. The method is officially documented, and tools for doing it are officially available from IFI. I think it's a perfect way to implement force feedback, or just about any other kind of feedback you want.

[Dave Flowerday]

Originally Posted by Alan Anderson

The rules do let us connect externally-powered portable computing devices to the OI. The method is officially documented, and tools for doing it are officially available from IFI. I think it's a perfect way to implement force feedback, or just about any other kind of feedback you want.

Not quite:

Originally Posted by R66

Teams are permitted to connect a portable computing device (Laptop computer, PDAs, etc.) to the RS232 Output of the Dashboard Port of the Operator Interface for the purpose of displaying feedback from the robot while competing in Competition matches. Please note that AC power will not be available at the playing field so these devices will have to run on internal batteries.

Originally Posted by R69

All equipment connected to the Joystick Ports of the Operator Interface must be powered solely through the power available through the port. External power sources of any type are not permitted on any equipment connected to the Joystick Ports. Portable computing devices may not be connected to Joystick input ports on the Operator Interface.

You may only connect externally-powered devices to the dashboard port. Any device which is connected to the joystick ports may not use external power.

Now I suppose you could try to pull something off where you took a normal joystick and wired in some feedback motors that were controlled by signals coming from the dashboard, such that the feedback circuits were totally isolated from the joystick port circuits, but in my opinion this would really be bending the rules. I would consider such a contraption to be a single "device" and therefore it would not be allowed to be connected to the joystick port(s).