Re: Force Feedback
 

Aha! You figured out the solution. All you need is a simple circuit with a microcontroller, an rs323->ttl level shifter, two motor drivers ( something like an L293D would work), and a simple power supply, and two motors.

Re: Force Feedback
 

that only works if you dont have a computer conected to that port. But if you change the LED color as said before i think the ports will as well receive that signal.

for example:
On Joystick # 1 and 3:

Pin:
15= Pwm1_green
08= Pwm1_red
09= Pwm2_green
05= Pwm2_red

Just add a 3.0V radioshack hooby motor with its power connected to each of these and then add the bands or whatever to give you the power resisting your push.

Remember we are not trying to actually move the joystick here with alot of torque the intenstion is merely to provide a little user feedback, a 3V motor running at 5V is safe and it will be kinda noisy and will heat up like any motor if it stalls so i would try to avoid making the feedback run alot to avoid burning out a motor.

Re: Force Feedback
 

Rather than connect a 3v motor and run it at 5v it might be a little wiser to connect something like a 12v motor and run it at 5v. This way you wouldn't have to worry about thermal issues as much. The off the shelf force feedback joystick i have uses motors that are HUGELY oversized. They are approximately the size of the motors on the FP gearboxes that come in the kit. In any case, you are going to need some gearing in there somewhere. I would still recommend some sort of power storage circuit if you want to try this. I can help out with the design of such a thing if somebody wants to try it.

Re: Force Feedback
 

Could you wire the LED outputs to a on/off switch sort of like a victor but running on voltage, not a PWM signal, then to force feedback motor(s). Then the motors would be powered by a random battery, since the circuit isn't in a tether or joystick ports, it doesn't really matter. The victor(ish) thing acts as an amp to power the motor and it doesn't break any rules as far as I see, and could have tons of power if you needed it.

Re: Force Feedback
 

It doesn't say electrically connected, it says connected.

Re: Force Feedback
 

Re: Force Feedback
 

I think that I will try and do this with either 3V or 12V motors and see what happends but when i do i will certainly post a how-to for anyone interested.

And for power storage would a few dozen 2500(mu)F capacitors be enough?
(I took them off of a motherboard hoping theyd be more useful than an old dead mobo.

Re: Force Feedback
 

Nope,
A 3v motor running at 5 volts is still in stall when you start it. The little Radio Shack motor will draw amps when starting and the LED ports can only source 10 ma. That's not 10 ma before cutout or 10 before OI shutdown, it's 10 ma period. Damage to the OI could result. These outputs are specifically designed to feed LEDs and nothing else. Capacitors, like motors, look like a short when you apply power. To have enough to store the current required for a motor would take a week to charge up at 10ma and "NO" you can't charge them up before a match. There is no way around the rules for the OI at the present time.

Re: Force Feedback
 

So if I understand you correctly it will not work because the 10ma is not enough to power the motors and the power required to power them would damage the OI?

Re: Force Feedback
 

Not exactly, just hooking the motor up and turning on the output could damge the OI. The motor appears as a short when power is applied. All DC motors exhibit this charachteristic.

Re: Force Feedback
 

Ok I think i get what you're saying now, is there anyway that I could prevent a short from appearing then when I turn on the motor initialy?

Re: Force Feedback
 

No,
All motors are in stall when they start and will draw stall current for a short time before turning and up to speed. Just look up stall current and it will give you an idea how far away you are from using the output for motor drive.

Re: Force Feedback
 

I still belive that with a suffeciently advanced power supply, intermittent force feedback is possible.

Somewhere in this thread it was mentioned that 100ma is available of the +5v aux. Lets play it safe and not draw more than 75. That gives us .375w to play with (5x.075). Now lets say out power supply is 80% effecient(pretty conservative) at storing and converting power:
.375x.8=.3w

Lets say we want to use a motor with a 300ma stall current running @ 5v. Thats 1.5w (.300x5).

Ok so we have .3Joules/Sec(watts) available to us. We need 1.5Joules to run our device for 1 second. What percentage of the time can we run our device?
.
.3/1.5=.2 We can run our force feedback thingly 20% of the time!!!. If you are running into things 20% of the time you are in trouble! I should mention that this is an absolute worst case. Most of the time you will not be operating your feedback motor at the full 5v.

How about the amount of energy that we store up during autonomous?
5 x .075 x 15 x .8 = 4.5J Thats enough to run our 1.5 watt device for 3 seconds.

We would probably need an energy storage/current limiting curcuit and a DC-DC boost converter but thats not as scary as it sounds. TI provides a large line of power supply building blocks that require few external components. The current limiting curcuit can be accomplished with only a small handful of discreet components. The energy storage can be as simple as a large capacitor.

How about if we just want to install a tiny vibrating motor in the joystick handle to notify the driver of something. heres one that will do nicely. It runs off 62ma at 3v. thats .186 watts. If we again assume an 80% conversion effeciency we can run this thing constantly and have power to spare.

In none of these examples did i even begin to draw off the LED power. There are 8 LED outputs. The spec sheet claims they provide 10 ma each. Thats a whole 80ma more that could potentially be tapped!!

---------- edit -----------
Now that i think about it we have two axis so we will probably have 2 feedback motors. which means twice the power needed.

Re: Force Feedback
 

Unless we do as you suggested before and use only a single motor in vibrate for high current alert or maybe speed.

Is there a way to prevent capacitors from looking like shorts? Heres what I'm thinking: As rickertsen posted above, we can run a single vibrate motor off of the current supplied by the OI. I havn't looked at the stall for the motor he suggested, but if we can use a capacitor to supply the stall current for the motor just long enough to get it spinning, it might buffer the input long enough so that the stall position of the motor won't be seen by the OI. It shouldn't take much to do this, so our capacitor could charge almost instantly. I think thats right...

Re: Force Feedback
 

OK,
Let me go into the long explanation on this so everyone will understand. First and foremost, the input power to the OI is 1.5 amps, period. That accounts for all the internal power, all interface electronics and all I/O including the LED ports. Each LED output is current limited to 10ma by an internal resistor. If you were to measure the output voltage with nothing connected (No current flowing) you would measure 5 volts. Add a load of any type and the output will fall to the load resistance times 10ma( thanks to Ohm's Law! V=I*R). In the case of an LED this will be about 2 volts. Next, the so called "Aux" supply is intended for feeding pots in either joysticks or external INPUT devices only. To fool with this supply risks the OI interpreting any/all joystick input as something other than 127 and sending the robot off to damage itself, the field and the other robots and people around it. Finally, a dead short is still a dead short and there is no black magic that can fix that. A similar motor that was supplied to teams a number of years ago had a stall current of over 12 amps. Although Radio Shack does not rate this motor, expect it to have a stall current of at least 3-5 amps. Attempting to interface a motor with any combination of electronic tricks will pull the OI power down, possibly causing damage, blowing the Aux fuse in the OI and likely preventing you from playing the match if this were to occur on the field.

There is no way to fool a capacitor into being anything other than a short when it is discharged. You may not precharge an OI device under current electrical rules.