victor 885 parts

[Cirrussport]

I know they arent used in first but does anyone have a victor 885 that they could pull a part number off for me if its possibly visible?
I need the part number for the fets used.(these are the parts under the fan)
Thanks so much

[Mark McLeod]

Victor 885's use International Rectifier IRF3703 FETs.

[Cirrussport]

awesome, thank you so much.
Do you know if they use the same Pic micro controller?
Ive tried to find the microcontroller with some success. Just trying to replace blown parts on one. The microcontroller isnt blown but i wouldnt mind getting a backup to copy the program too.(you never know what could happen)

[Mark McLeod]

I don't know which microprocessor is used in the Victors. I remember locating it on an 883 or 884, but I don't think I went so far as to figure out which model it was. The program is not in the microprocessor, but on a nearby firmware chip. If any of that blows you've got bigger problems than replacing the microprocessor.

[Al Skierkiewicz]

It seems that I remember reading a statement somewhere that the 885 is a different beast than the 884. Besides the fact that it uses the higher voltage FET.

[Cirrussport]

i didnt notice any firmware chip. The microprocessor has all the built in memory and space to store the program.I see a few voltage regulators, 12 mosfets. A Capacitor. A few small other chips(i dont have one on me right now but i didnt think i saw a firmware chip. Theres also a few little pieces like the frequency chip which i believe runs the mosfets. Altho there are tons of little resistors.

I just have like 6 victors sitting around that are blown and want to fix them. There mostly 883's but thought i may be able to replace the mosfets with higher voltage mosfets to stop them from igniting and burning out. I dont know how well it will work but i think its worth a try. Unless someone else has tried it

Thanks

Craig

[Mark McLeod]

Forget what I said about the firmware chip. I was thinking of another system and confused myself.

There is more to blowing up FETs than their individual ratings. Put too powerful a FET in as a replacement and the rest of the Victor won't be able to handle it.
I agree with Al's comment that the 885's are a different beast. They handle higher power because they are designed for it with features other than "bigger" FETs.

Usually, the FETs short when metal shavings or particles fall into them. Bigger FETs might just release more magic smoke.

[Richard Wallace]

Originally Posted by Mark McLeod

... There is more to blowing up FETs than their individual ratings. Put too powerful a FET in as a replacement and the rest of the Victor won't be able to handle it. ...

FET's that are rated for higher breakdown voltage and/or for lower on-state resistance will also have higher gate capacitance. A driver circuit that is correctly sized for a lower-rated FET may not provide sufficient gate current to fully saturate a larger FET within the same switching interval; this would result in higher switching losses, so the larger FET might actually run hotter, depending on the chopping frequency. As Mark says, you should not try to soup-up a Victor by simply changing out FETs -- you have to consider the whole circuit.

[edit]666 posts![/edit]

[Al Skierkiewicz]

Not to pile on here,
As Mark has pointed out, FET death is frequently metal shavings related but all too often, teams are running inefficient designs that have extreme current demands (i.e. constant or near constant stall on a Chalupa will draw 129 amps). It is these extreme currents that raise the internal temperature that explodes the case of the FET. (Note that the FETs are not mounted to heatsinks.) Going to a higher breakdown voltage FET will do nothing for that type of failure. In general, a single FET failure is shavings related and will usually be accompanied by smoke damage near the base of the FET. A failure of six at a time is temperature related and will usually result in damage to the circuit board.

[Joe Johnson]

Originally Posted by Al Skierkiewicz

Not to pile on here,
... ... A failure of six at a time is temperature related and will usually result in damage to the circuit board.

Many competing products to Victors protect themselves from thermal destruction by having the micro onboard the Electronic Speed Controller (ESC) monitor current and/or temp flowing through the ESC.

Back when I was a rabid robot warrior, I thought that I wanted every ounce of performance from the ESC. I reasoned that I would rather replace any dead ESC between matches than loose a pushing match because the ESC was protecting itself.

I have since moderated my views. If everyone has the same constraints, it doesn't really hurt the competition to have everyone with a little less current capability in the ESC -- it's just one more constraint everyone has to live with. The main result of an ESC that protects itself would really just be lower sales of ESCs because fewer die and teams don't have to buy replacement/extra ESCs.

Bottom line, I think it is a good idea for ESC's used in FIRST to have internal thermal protection.

Joe J.

[Cirrussport]

i fully agree with the thermal protection idea. i have so many dead victors sitting around just because of over current. I wouldve much rather had the victor limit the current or cut out because of heat then had to replace them. Thermal protection should definately be considered.

I like the overall victor design. but thermal protection would be great.
I know it wouldnt work in first competitions. but i think it would be nice to have a full 2 victor system with mixing capabilitys available for r/c equipment. I like the victors much more than the double esc mixing systems out there

[Al Skierkiewicz]

Originally Posted by Cirrussport

i fully agree with the thermal protection idea. i have so many dead victors sitting around just because of over current. I wouldve much rather had the victor limit the current or cut out because of heat then had to replace them. Thermal protection should definately be considered.

The thermal rise is so fast that there is no effective way to compensate for that electronically. ( it is likely that the temperature rise is fast enough that even heatsinks would not fix the problem.) At the time that the overcurrent is taking place, the branch circuit breaker was already tripping, several times. A non resetting circuit breaker would cure the damage problem but make it impossible for you to continue to compete. It is essential for teams to measure current in motor circuits while practicing in order to insure no damage to motors or to Victors. Remember that for all intents and purposes, a stalled drive motor (Chalupa, FP, or drill) looks like a dead short to the Victor. A device that is rated at 40 amps cannot sustain a 2.5x overcurrent for very long without damage. You have proved that. P=I^2 * R, with an ON resistance of .002 ohms and assuming that each FET is sharing 1/3 of the load, you have a potential for a junction dissipation of 10 watts. That little piece of silicon can't get rid of the heat fast enough.

[Joe Johnson]

Originally Posted by Al Skierkiewicz

The thermal rise is so fast that there is no effective way to compensate for that electronically. ( it is likely that the temperature rise is fast enough that even heatsinks would not fix the problem.)...

I disagree. Here is a FET* that has internal thermal protection plus current feedback that could be used to implement protection running on the ESC's micro.

Joe J.

*This is just the first FET I found on the IR website as an example. It is not the right FET, but there are many like it that would be suitable for a FIRST ESC.

[Al Skierkiewicz]

Joe,
The 3113 is a very interesting device and has the possibility of some serious applications using current sense, but it is a little beyond what the Victor needs. In comparison with the IRL 3103 FET currently supplied with the 884 it can deliver 64 amps vs. 7 for the 3113. If they were able to handle the current the cost per unit is almost $2 higher than 3103 (single unit quantity) for an added cost per 884 of $24. Even though the 3113 has a pulsed peak current of 100 amps, that is under specific conditions. The internal temperature shutdown is sensed inside the package and shutsdown the circuit while it waits for the temp to cycle down. Since this is not an external control the individual units would be cycling on and off at different times dependent on internal temperature, leaving the remaining online units to share the higher load.

[Cirrussport]

Now im just going over the design of the victor. Ive got one blown one that im just playing around with trying to figure out exactly how it works. as far as i can tell its basically a microprocessor controlled h-bridge with 3 mosfets per section of the h-bridge circuit. I see a few voltage regulators that im guessing are to run the micro controller and the the gate on each mosfet.