According to the manual, the jumper to set brake/coast on the Victor can be replaced with a limit switch - not particularly useful. According to the custom ciruits rules, we can’t make something to replace the jumper. I’m also assuming that a relay or transistor would fall under the category of custom circuit. I just wanted to make sure that I’m interpreting the rules correctly. It just doesn’t seem like that great of an idea to actuate a limit switch with a servo or soleniod or something to dynamically change the setting.
Last year there was a thread about this. The way to do it completely within the rules, is to use a servo to act on the “limit switch.” This year there is no rule limit on how many servos you use on your bot, there will be a point where you run out of places to plug them in.
I’m not certain of any of the rules and I don’t make any claims on the legality of this but look at it this way, what is a jumper? What is it’s purpose? It bridges the gap between two pins. A physical electrical conection. What if instead of that little bar of metal, you had a wire connecting those two pins? What if this wire became an inch long? Then why not a foot long? And what if cut this wire right in the middle and install a switch. Opening and closing this switch would have the same effect as placing and removing the jumper.
Well, my goal was to use a relay or something so that it can be controlled in software. Useing a servo to actuate a switch doesn’t seem very efficient - or fast - to me.
You might surprise yourself. Use a switch that is easy to “open” and “close” like a limit switch with one of those long metal strips.
We have done this with an array of relays for the last two years and had no problems with inspection. I havn’t read the rules carefully enough to see if it is legal this year though.
------------------- Edit --------------------------
It Looks to me like Rule R51 prohibits this sort of thing. There may be a loophole however. I believe that all the jumper does is pull a pin either high or low. there is no rule that i can see that prevents you from directly connecting this pin to a digital output. I wouldn’t consider this a “custom circuit”. This may be a loophole but i feel it does not go against the spirit of any rules. You are not providing a PWM outpur, not directly controlling movement and not posing a safety rist. BTW I believe the signal pin is the middle one.
This method (direct connection to the controller) was addressed last year in Q and A on the first site, and as I recall was not allowed, The relay method would seem logical even if you have to drive it with a spike. I would suggest spell out exactly how, including a wiring example and submit it to the Q and A process.
Thanks in advance -Biff
Please keep in mind that many rules are made to prevent damage to IFI hardware or to prevent bodily harm. (It’s expensive to replace.) Using a limit switch prevents any team from connecting power supply to one of the pins. It is also to prevent a team from using underrated electrical components from supplying power to the motors. A fire on the field could rain on everyone’s parade.
If anyone posts a Q&A on this, please post it here. It doesn’t seem like there should be anything wrong with driving it with a digital output.
The digital outputs are powered from the controller. The brake/coast jumper is powered from the Victor. Directly connecting two power sources is what they are trying to avoid here. A dry contact switch is what is required to replace the brake/coast jumper.
Don’t make these kind of assumptions. A closing (dry, no voltage) contact is what is required.
Q&A says that the relay is fine as long as it’s allowed by the part use flow chart. Pretty much, if you can get a relay from the approved vendors, it’ll be fine.
I know that the vics can go into break mode when the jumper is in one position, anyone know which that is (left or right). The help file doesn’t show it. Thanks!
If I remember right, when the jumper is in position A-B, the Victor is in brake (not break) mode. When it is position B-C, the Victor is in coast mode. I also searched and found it in an old thread. I’m assuming things haven’t changed since then…
It should be pretty obvious if you have it in the wrong position when you test it out.
from the ifi manual
Brake / Coast Configuration
The Brake / Coast jumper is used to set the speed
controller’s action during a neutral condition. The Brake
provides significant resistance to motor rotation and is
recommended for motors driving linkages and arms that
can be back-driven by gravity or other external forces.
The speed controller checks the status of the jumper
approximately 60 times per second. This allows the user
to change from brake to coast during operation. A limit
switch may be connected to the jumper connector instead
of the jumper. The limit switch can be triggered by
various means including the use of a servo.
Brake / Coast Guidelines:
- The jumper should always be installed in either the
Coast or Brake position. If you lose the jumper, a
standard computer jumper will work.
- If no jumper is installed, the speed controller will
default to a Brake condition.
- The Coast condition sets the output to an open
circuit during neutral.
- The Brake condition sets the output to a short across
the motor leads during neutral.
if the pin is set to the left it is set to break
if the pin is set to the right it is set to coast
You can also directly access the Victor 884 User Manual to find other answers.
(I suspect you didn’t mean that he could find different answers. :p)
Interesting. The diagram in the manual only shows “B” and “C” (no “A”.) This is the way the Victors were the first year or two we received them.
Here’s your mnemonic*: Ignore the “A”, and remember that “B” stands for “Brake”, and “C” stands for “Coast”. Set the jumper nearest the “B” for “Brake” mode, and toward the “C” side for “Coast”.
*Mnemonic: n. A device, such as a formula or rhyme, used as an aid in remembering.
I’m curious to see which setting teams use for the Victors on their drive train. We used Coast last year, but while I was testing my new drive code, I set them all to Brake, and I felt like I had much more control. I’ll probably leave them on Brake when we build the real robot.
We’re just going to have to try it once we have something to drive. I have one question though. Are there any downsides/problems with braking only one motor in a dual motor gearbox?