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#16
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Re: FisherPrice Problems
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Bruce |
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#17
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Re: FisherPrice Problems
Bruce,
The 336, as with most clamp on ammeters and VOMs are only good to 400 HZ. The output of the speed controller is a 2 kHz rep rate so the pulses are even shorter than that. That allows for a lot of error to build up at less than full throttle. I am guessing that you might be reading 50-60% of what is actually taking place. It is a good tool to check between motors and will give accurate results when the controller is producing full throttle. It is a tool many teams don't have in their tool box but should. |
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#18
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Re: FisherPrice Problems
Heat sinks most likely will not solve your problem. Take a look at the gear box motor mounting. Did you block any vent holes? If so see if there is a way to reestablish the motor venting. The small can motors rely on the integral fan to move air and provide cooling. If the motors are venting then the load must be reduced.
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#19
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Re: FisherPrice Problems
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#20
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Re: FisherPrice Problems
Check the IFI specs. The 883 was about 2k output feq. The output feq of the 884 is low about 120. This was done to give control below 10%. Using a UEI digital clamp on amp meter VS an old Amprobe analog clamp on I'm getting less than 10% variation in current readings.
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#21
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Re: FisherPrice Problems
Quote:
Bruce |
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#22
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Re: FisherPrice Problems
I looked on the IFI website for both the 883 and 884. Last fall there was a post in the IFI forum looking at the differences between the 2. IFI detail the differences in the switching feq. Seams they have cleaned the posts up for the 2006 season and it's not there. Would have to be re asked or give IFI a call to confirm. There where some threads where this topic was discussed on Chief Delphi. Again check the motor mounting blocking the vent slots. There was another post concerning this.
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#23
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Re: FisherPrice Problems
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Has anyone ever thought of making aluminum blocks to mount to the motor, and storing them in a cooler of dry ice between matches? Actually... you may loose most of the cooling by the time the match gets started... just a thought... |
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#24
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Re: FisherPrice Problems
Quote:
Matt |
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#25
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Re: FisherPrice Problems
Try reading the current after the breaker, going into the victor.
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#26
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Re: FisherPrice Problems
Quote:
The problem is that the Cp of metal is just not that high -- meaning you can't store that much heat energy in them unless a phase change is involved (i.e. melting the metal). In my opinion, even heat sinks on the outside of the motor can are of only marginal usefulness. Yes, heat sinks will make your motors able to runs somewhat higher current in steady state, but FIRST is not really steady state. Our uses come in bursts. Heat transfer takes time (especially conducting heat out of the windings of the armature, through the air or the shaft to the outer can to the thermal grease to the cooling fins). By that time, your windings are toast. Air blowing across the armature -- now THAT is cooling. Keep your current down and your armature speed up (1/4 of stall torque) and you'll be fine. ...you mileage may vary... Joe J. |
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#27
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Re: FisherPrice Problems
Quote:
The difference between the probes is pretty good. Still if you want to have accurate current data you must use another method. i.e. if you want to correlate current and breaker heating. After a diligent search of the archives, I did find this... http://web.archive.org/web/200410222...3datasheet.pdf It lists the 883 at 2kHz. However this sheet compares the 883 and 884 as having different deadband characteristics and the 884 being programmable as to the deadband. http://web.archive.org/web/200208052...Victor_884.htm Last edited by Al Skierkiewicz : 15-02-2006 at 08:24. |
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#28
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Re: FisherPrice Problems
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We found this:http://www.ifirobotics.com/forum/vie...61922d031d945b But I'm still not sure what that means. Is it talking about a code loop rate, victor input sample rate, or victor output pulse rep rate? I think somebody's gonna have to hook up a 'scope. |
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#29
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Re: FisherPrice Problems
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#30
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Re: FisherPrice Problems
Victor 883 - 2000 Hz
Victor 884 - 120 Hz Direct from the designers. -JV |
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