Re: Advantages of the Jaguars?
 

Scott and Bill
I guess the question then arises, is this an "or" function? The fan turns off after 10 seconds or the temp is below 38 degrees? Is the temperature sensor part of the circuit board or is it attached (thermally) to a FET? I am asking since we have not yet opened one and it will be a while before we get back into the shop.

Re: Advantages of the Jaguars?
 

Ditto here.
You mean aside from integrated end-limit switch inputs, a far more linear response curve and range, thermal and overcurrent protection, smart fans, clearer markings (can't miss that red screw) and better cost, all of which the Jaguars have and Victors do not?


.

Re: Advantages of the Jaguars?
 

If you can't make them fit on the robot, then those features don't really add much value.

Re: Advantages of the Jaguars?
 

Actually, I'm going to have to vote against the screws.

If the screws were captured, that's one thing. However, they're not. And they're very easy to completely unscrew. They're also not error-proofed and can be put back in the wrong holes.

The result is that someone could accidently wire them backwards. I'd much rather they get rid of the colored screws and color something that can't be reversed or removed.

I understand that a bit of caution prevent this issue most of the time. But I don't think that anyone can argue that if it CAN happen, it WILL happen.

Re: Advantages of the Jaguars?
 

We've released the magic white smoke on a number of Victors in the past few years, and to our knowledge, we hadn't done anything wrong, (aside from not being careful enough with metal shavings falling in). I am, however, more inclined to believe you. What could we have done wrong to burn them out? What happened to you guys?

Hopefully with this knowledge and some care, we won't burn out any more victors, or jaguars if they are prone to the same weak points.

Re: Advantages of the Jaguars?
 

As far as I know, we've only had one Victor fail, and it seems to have been bad in the box, because it did not work when we first put the robot together, and we always treat the Victors carefully. That's still a pretty good success rate.

The room issue...hmmm....looks like our new chassis design

http://www.chiefdelphi.com/forums/sh...threadid=70758

has plenty of room for Jaguars.

Re: Advantages of the Jaguars?
 

If you're constantly burning up any electronics, I'd reassess your work practices.

Are you drilling over the robot? If so, are you covering your electronics with a towel or something else to prevent chips from falling in them?

Have you dropped screws, nuts, etc into the robot?

Have you used a compressed air line near the robot and potentially blown metal chips into it?

Victors don't just smoke themselves of their own accord, so there must be something that's user specific that is causing them to die.

As to what we've done, chips in the robot have caused problems before. A chip shorted out our RC and fried it in Hawaii last year. The program connector and power connectors have been sheared off the RC due to mishandling.

If you're careful with all of the electronic items we get in the kit, they should last you a long time, regardless of who made them.

Re: Advantages of the Jaguars?
 

I completely agree. In 2006, our RC stopped working during competition, and we eventually figured out it was because a metal chip had landed in the pins. Ever since then, we've been careful to cover the electronics whenever we worked on the robot, especially when drilling holes. We haven't had any problems since.

Re: Advantages of the Jaguars?
 

Last year we burnt out 2 or 3 victors between build season and four competitions. The compressed air and the holes were probably our weak points. We usually cover the electronics and hold a vacuum to the drill, but at a few points we may have gotten lazy. Sometimes the mentality spreads that all chips can simply be cleaned up later before we turn the robot on, but that clearly must be avoided.

Re: Advantages of the Jaguars?
 

The fan is controlled by a separate, smaller, MOSFET; the fan is not controlled by the H-bridge.

The fan turns on whenever there is a non-zero voltage produced at the output. The fan turns off after the following three conditions are met: a) the output goes to 0 V, b) 10 seconds have passed, and c) the internal temperature is below 38C. If the temperature is not below this threshold, the fans stay on after the 10 s period.

Re: Advantages of the Jaguars?
 

AND function.

The temperature sensor monitors the ambient temperature; it isn't attached to a specific MOSFET.

Re: Advantages of the Jaguars?
 

Scott,
Can you disclose the type and number of Power FETs used in the Jaguar? I don't have access to one for a while during the holidays.

Re: Advantages of the Jaguars?
 

Sure can. Jaguar is a design example, so the information for it is pretty available.

3 Fairchild FDP8874 MOSFETs for each quadrant of the H-Bridge; 12 in total.

Re: Advantages of the Jaguars?
 

You can get a lot more information from Luminary Micro's Non-FIRST specific site. http://www.luminarymicro.com/products/mdl_bdc.html

Re: Advantages of the Jaguars?
 

I'll bite, as no one is on some of these things. These are all for 2009, as 2009 is the season people are debating right now. I don't care what will be enabled later or what they can do later on right now (I'll be stoked when they are though), I just care about what they do right now.

End-limit Switch Inputs; In the past few years, I've used limit switches only on one mechanism, and we wanted the state of that switch for other operations in the code. So, we can wire it directly to the controller and just toggle the motor on and off, OR we can build a little circuit (another possible failure point) that has to be plugged into the jaguar and the controller? I'm completely not fine with having the limit switch only connected to the jaguar and the controller not knowing the state, that's just potential for disaster.

Far More linear response; I have yet to see them tested on one of my team's bases, but I think this may be the jaguars one true advantage. Smoother control, sounds good to me.

Thermal and overcurrent protection; I'm always the guy on the team trying to push components to their limits, trying to get that last competitive drop of performance out of them. Since my 2005 season (only because I can't recall back further), I've never seen a motor burn out on a competition robot, and only have ever seen on victor fail (due to faulty wiring) which wasn't due to overhearting. This is really a non issue with me. Sure, it's great, it's a feature... but it's not addressing something that was a problem with the Victors.

Clearer markings; Oooooh... my team has heard a lot of this one from me. The markings (as other people have said) are actually WORSE than before... you mark the screws? Well, I've seen kids take off both screw per side to wire up, not good practice, but it happens. If they get put back backwards once, human nature will probably keep it from being noticed for a while. I imagine inexperienced teams having an epidemic of problems with this.

Better Cost; This one really changes on a team per team basis. For my team, when we compare the categories for selecting speed controller, we won't simply say, "Oh, the Jaguar is $75. That's way cheaper than a victor. Lets use that". We're going to look at the total cost. Right now, we have 13-15 Victors ready to go for next year, and 4 Jaguars. If we decide on all Jaguars, and possibly up to 20 speed controllers, that's a lot of money, substantially more than just trading for a few victors.

So, right now, for this season, the one advantage (for non rookie/2nd year teams with minimal victors on hand) is the smoother performance. For right now, that's not enough to outweigh what our team see's as the cons. For the 2010 season, I expect the debate will be entirely different, but the fact is, I'm not worried about the 2010 season at this time.

I really hope people will weigh all the pros and cons rather than just citing how "improved" the jaguar is.

This isn't coming from a bias towards IFI either. I love IFI, think they're great people. I also love AndyMark, think they're great people. But if someone else comes out and markets a better speed controller and a better 2 speed COTS gearbox (assuming both legal to use), we're sure as heck going with the better stuff.

But hey, if any of you guys want to get rid of those terrible victors, my team would be willing to trade and take that burden off your hands.