Blown Victors - WHY?

[wmurphy]

We built a prototype robot that worked fine using a base plate of press board to mount the electronics; however, when we changed the press board to a metal plate - TWO VICTORS BLEW! What is the problem? Continuity tests check out O.K. Victors did not blow until joysticks were moved.

[jgannon]

Were you cutting metal around them? If you happen to get metal shavings inside, they will burn out very easily. This is apparently a fairly common problem, though I can't imagine why people actually do this.

[DarkJedi613]

Did you drill holes in the metal plate near the electronics? If so you may have gotten scraps of metal into the Speed Controllers causing them to short. We had that problem last year.

[wmurphy]

Originally Posted by DarkJedi613

Did you drill holes in the metal plate near the electronics? If so you may have gotten scraps of metal into the Speed Controllers causing them to short. We had that problem last year.

We were fairly conscientious about making certain that at least the second victor was "metal scrap" free. At this point, I'm kinda "gun shy" about moving back to the press board even ...

[DarkJedi613]

You could take the screws off (and void the warranty) to see if there are metal scraps in it. Its much easier than it seems to get metal in them. Ideally you want to take the electronics off when doing things like that.

[Cody Carey]

Originally Posted by wmurphy

We were fairly conscientious about making certain that at least the second victor was "metal scrap" free. At this point, I'm kinda "gun shy" about moving back to the press board even ...

If its the aesthetics you are woried about, then why dont you mount the electronics on Plexiglass or Lexan?

[DarkJedi613]

If you do find out it is the Fets that are causing the problems, you can replace them much cheaper than replacing the entire speed controller. I believe it voids your warranty but Fets are quite cheap - maybe $.75 or so each.

We also developed a tester for speed controllers to see if they're working or not, I don't know the specifics on that however. I'll find out later and post more.

[roboticsjenkins]

Originally Posted by DarkJedi613

If you do find out it is the Fets that are causing the problems, you can replace them much cheaper than replacing the entire speed controller. I believe it voids your warranty but Fets are quite cheap - maybe $.75 or so each.

We also developed a tester for speed controllers to see if they're working or not, I don't know the specifics on that however. I'll find out later and post more.

They blew because you probably grounded the Victors out because I had that problem last year. It's better to mount them on a piece of material that is not a conductor of electricity......Thats my guess

[Al Skierkiewicz]

Originally Posted by roboticsjenkins

They blew because you probably grounded the Victors out because I had that problem last year. It's better to mount them on a piece of material that is not a conductor of electricity......Thats my guess

Andrew,
The case of the Victors is an insulator. We mount our electricals on a punched aluminum sheet and have never had a problem.

"From DigiKey: IRL3103-ND"
It is really interesting if you take a look at the data sheet on these little gems. http://www.irf.com/product-info/data...ta/irl3103.pdf Note under maximum ratings, that continuous current is 64 amps and pulsed current is 220 amps per device (limited by junction temperature). Remember that there are three devices in parallel for 64 x 3=192 amps as long as you can keep the little buggers cool. When teams blow these up, there is some extreme abuse occuring. High currents over long periods of time, heat and/or metal flakes in of near the devices spell destruction. Changing FETs is not a guaranteed fix, other devices may be destroyed when a FET(s) short.
Please note that the Drain and the tab of the package are connected together. That means that the tabs of half of the FETs in the victor are connected to battery positive and the tabs of the other half are connected to motor positive. Keep conductive material away from the FETs.

[DarkJedi613]

Originally Posted by Al Skierkiewicz

Changing FETs is not a guaranteed fix, other devices may be destroyed when a FET(s) short.

Yeah, I know - if you blow the board its just gone (though you can save the muffin fan!).

One of our mentors created a tester to see what was wrong with the Victor, I'll see if I can get a wire diagram and pictures of it.

[Der Sichelmann]

Of the victors our team has blown, the problem has always been FETs. We have been able to repair them.

[wmurphy]

Originally Posted by DarkJedi613

If you do find out it is the Fets that are causing the problems, you can replace them much cheaper than replacing the entire speed controller. I believe it voids your warranty but Fets are quite cheap - maybe $.75 or so each.

We also developed a tester for speed controllers to see if they're working or not, I don't know the specifics on that however. I'll find out later and post more.

Just curious - do you know the FET part #s and a good source for them? Thanks!

[DarkJedi613]

Originally Posted by wmurphy

Just curious - do you know the FET part #s and a good source for them? Thanks!

I do in fact - I just have to find it.

From DigiKey: IRL3103-ND
($1.64 ea., $1.16 per 10, $.96 per 100)

Mouser also has them (search for IRL3103)

Also we know for sure that we got metal shavings in when we blew them - we took them out when we took the Victor apart.

I'm going to attach a PDF spec sheets if you want to check it out yourself. (The Victor fet specs are too large to attach, but I'll email it to anyone who wants it.)

[Der Sichelmann]

Originally Posted by DarkJedi613

Did you drill holes in the metal plate near the electronics? If so you may have gotten scraps of metal into the Speed Controllers causing them to short. We had that problem last year.

After our experience, we are extra careful Our engineers built a tester to find bad controllers and we ordered the parts to fix them.

[Andy A.]

Top four reasons why Victors 'blow'.

1. Metal shavings shorting out the power FET's
2. Reverse polarity. The new housings this year don't mark which terminal is which, so this could happen easily enough. I believe that
3. Being dropped.
4. Angering the electronics god.

Not much you can do about any of those, except #4. If thats the case, sacrifice 12 Dews upon an alter of Bridgeport consecrated by WD40 on the eve of ship date.

-Andy A.