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Originally posted by Justin Stiltner Just to give everyone an idea if you really really want to use your joysticks with the r/c gear open up the transmitter.. it uses pots to read the sticks, simply take those out transplant them into your joystick.. or measure the resistance on em and get some extras and extend the wires and your all set. You can buy extra transmitters only for around $45-50 or so. Personally I have been wanting to drive the robot with my r/c transmitter for a long time.
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An EXCELLENT idea Justin, but it depends on the circuitry in the transmitter.
First off, PC Joysticks are set up as roughly 100K
RHEOSTATS (actually, I've measured 90K +/-5% on the Flightstick). IOW, you don't get all three wires to the pot out to the connector, only one end, and the wiper. In addition, the WIPERS are common, and there's no extra wires in the cable to bring out the other end of the pots.
In a PC application (as in the robot controller), this variable resistance is used with a capacitor in the interface, to create a R-C timing circuit. (That's "Resistor-Capacitor", not "Robot Controller" or "Radio Control"... Too many RC acronyms around here!!!
)
Now if your transmitter is
also using an R-C timing circuit (older R/C transmitters used 555 timers too, just like the early PC interfaces), then all you have to worry about is matching the RC constant. If your pot in the transmitter is a different value, simply change its associated capacitor value so that the value R*C is the same as before with the Flightstick's pot, and you should be all set.
However, if your transmitter is a newer, microprocessor controlled one that uses the pots as a Voltage Divider like the robot controller Analog Inputs (one end to +xx volts, one end to ground, and the middle wiper is some fraction of that voltage depending on position), then the pot's value is NOT critical, but you'd need to REWIRE your Flightstick. Not a problem if you have the cash to buy another set of Flightsticks, but remember we will no longer be getting new Flightsticks each year. Veteran teams have to
reuse their old Flightsticks from now on, so don't trash them up without replacements!
My recommendation in that case is to either:
A) Buy a cheap set of joysticks for the r/c, or
B) Leave the cords on as-is and add a NEW set of connectors to the sides of the joystick cases and bring out
all of the pot wires to them. However, since the joysticks have common wipers, you may also need a switch to separate them.
Unfortunately, current robot build rules FORBID OI joystick modifications of ANY kind, so if you can't use them as is, your best bet is to buy extra Flightsticks or a cheap set of PC joysticks for the transmitter that you CAN rewire.
FYI, I have made a schematic of the Flightstick, and have included the
full PC Joystick Standard Connector Wiring as a legend (all
four buttons and pots), so when we get that far, I can provide it to everyone to help with their modifications.
A quick question for someone to check that has a working robot and a Dashboard Monitor rig all set up: Which way is it? Is the variable's value in the robot program equal to zero, or 255 when the Flightstick is held at the upper left hand corner and the thumbwheel rolled forward? (That's the minimum resistance value positions.) I'm guessing zero, but I don't remember...
EDIT:
BTW, I
also wish to know the directional relationship between program variable's 0-255 value and the 1ms-2ms PWM signal... THAT will help us here, too. Thanks!
/EDIT
Please check all three channels (X,Y,Thumbwheel), so I can also verify my directions. I wish to finish up the legends in my Flightstick schematic before I release it to the public, and still need that data.
Thanks!
- Keith