tha FET killa!

This topic has 37 replies, 7 voices, and was last updated 20 years ago by Charlie Brown.

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- March 19, 2004 at 8:38 pm #12060
  ph2t
  Participant
  Posts: 2088
  that s right! I ve wound my first motor, and what happended? bsst, ffft, pop crackle! I killed the 2×2 fet stack on my madforce 🙁 .
  
  It all started a couple of days ago. I scored some 130 size motors from the bettster, they are from the Tamiya tank kit thingy, betty knows more….
  
  Here s one of em:
  
  I pulled the bugger apart and unwound the stock coils. 70 turns in total! I then wound my own, 25 turns of .2mm (I think) wire.
  
  (the one on the right is the 25 turn)
  
  I had bought a custom bb (ball bearing) end cap from http://www.minizworkshop.com along with some other parts… I know, I know it doesn t have carbon brushes but for the moment who cares….
  
  (the one on the left is the new end cap, the right is stock)
  
  And here she is, yum! 🙂
  
  I connected this motor to a battery pack and the !@#$ screemed! The torque is bugger all but I hope to fix that with some neo magnets, anyone know where I can score good neo magnets from? I was thinking of that draconius dude at mzr.com
  
  Basically after running it around I noticed that I need like 2km s of space to reach top speed, lol…. After running it for about 2 minutes the car farted and smoke came out it s rear. Game over for the fets…..I guess I expected this, I mean, hey what can you do about a motor that has a resistance of less than 0.06 Ohms….
  
  So I ve started making a turbo….
  
  Stuff stacking when one set of these babies is (theoretically) equal to about a 9×2 stack and rated at 110Amps (datasheet)!!! Yeah baby….
  
  more to come…….
  
  ph2t.
  
  Edited by – ph2t on 19 March 2004 15:43:05
- March 19, 2004 at 8:58 pm #50165
  PandaBear
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  Posts: 1866
  Hope ya didn’t kill anything more than the FETs… blackeye:
- March 19, 2004 at 9:01 pm #50166
  ph2t
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  Posts: 2088
  I don’t *think* so…… Crap, now you’ve got me worried…….
- March 19, 2004 at 11:13 pm #50167
  micro_Amps
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  Posts: 1290
  You probably havent, hopefully when they blew they didnt short internally to the gates.
  There are a few other TO-220 fets around the 50-80amp range that should handle the current.
  Try some of the Mini4WD motors too, but at that resistance you will need to use a heatsink on the fets.
  :)uA
- March 21, 2004 at 2:34 am #50181
  jamiekulhanek
  Participant
  Posts: 2563
  Microamps, i have been looking around for some TO-220 FETs, not sure what to go for yet.
  
  My 9×2 Stack is just not good enough, my 19t motor (0.5mm) overheats the FETs, infact, the FET stack seems to only pass about 10A!!
  
  In theory, my 19t, Neo magnet, 10 degree armature, with ball bearings *should* produce the power of a Johnson 540.
- March 21, 2004 at 2:55 am #50184
  ph2t
  Participant
  Posts: 2088
  the damage……..
  
  and it @#$%^ stinks too! forgot what fried ceramic smells like, yuk!
  
  ph2t.
  
  Edited by – ph2t on 20 March 2004 21:56:32
- March 21, 2004 at 4:38 am #50185
  jamiekulhanek
  Participant
  Posts: 2563
  Be careful with those signal solder pads, they lift VERY easily.
  
  OUCH man that’s gotta hurt!
- March 21, 2004 at 4:50 am #50186
  jamiekulhanek
  Participant
  Posts: 2563
  BTW i wouldn’t FRIGG around with those cheap armatures, they are pure crap.
  
  Tamiya plasma dash….5mm high temperature diamond trued commutator…pure quality. NEVER lets you down.
- March 21, 2004 at 5:14 am #50187
  ph2t
  Participant
  Posts: 2088
  I’ve got a 7389 fet back on and it still works!!!!:) I’m happy. But now when trying to stack I need to remove that black box thing, the ceramic resonater….. There’s just not enough room to solder the stacked pads….arghhhh…………….
  
  ph2t.
- March 21, 2004 at 5:43 am #50188
  jamiekulhanek
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  Posts: 2563
  When removing the “black box” make sure all the legs “wobble” when you desolder them, just to make sure you don’t pull a plate out.
- March 21, 2004 at 5:44 am #50189
  jamiekulhanek
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  Posts: 2563
  My New Toy!!!
  
  Waddaya rekon?
  
  only $212 AUD
- March 21, 2004 at 5:46 am #50191
  jamiekulhanek
  Participant
  Posts: 2563
  Oh and if you break off a solder pad, its no issue, just trace the tracks that go under the “black box” back to the thru-circuit board hole and solder a wire in.
- March 21, 2004 at 5:47 am #50192
  ph2t
  Participant
  Posts: 2088
  nice bro but don’t hijack my thread biatch! :smiley2:
  
  doing a 4*2 stack now so I can handle that beastly motor of mine……
- March 21, 2004 at 5:49 am #50193
  ph2t
  Participant
  Posts: 2088
  Quote:
  
  Oh and if you break off a solder pad, its no issue, just trace the tracks that go under the “black box” back to the thru-circuit board hole and solder a wire in.
  
  yeah I took some photo’s whilst the resonator was removed so I can trace those lines….. I’m trying to re-construct the H-bridge circuit so I can understand how they get the brake function. All this info will eventually help me build my own turbo.
  
  ph2t.
- March 21, 2004 at 5:57 am #50194
  jamiekulhanek
  Participant
  Posts: 2563
  If i want to hijack this thread, i shall, and will. :smiley2::D
  
  I really dunno if a 4×2 stack will hold up against a 25t motor.
- March 21, 2004 at 6:06 am #50195
  ph2t
  Participant
  Posts: 2088
  we’ll the double did, I had a single and a double stack in the pcb and the single blew, the double was ok. go figure….
  
  ph2t.
- March 21, 2004 at 6:19 am #50196
  jamiekulhanek
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  Posts: 2563
  Try some thicker wire, .4mm is IDEAL for 25t.
- March 21, 2004 at 6:23 am #50197
  ph2t
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  Posts: 2088
  thicker wire reduces resistance? therefore increases current? and increases torque yeah?
- March 21, 2004 at 6:35 am #50198
  jamiekulhanek
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  Posts: 2563
  ah YEP. i think that the more wire on the armature, the stronger the magnetic field.
- March 21, 2004 at 6:52 am #50199
  ph2t
  Participant
  Posts: 2088
  Quad stack is now done:
  
  hopefully it will fit…..
  
  time for bead.
  
  ph2t.
- March 22, 2004 at 3:49 pm #50225
  jamiekulhanek
  Participant
  Posts: 2563
  Try making the solder on pins 1 and 3 a bit thicker, put a thin piece of wire along the pins to aid in making the solder stick and make a big fat solder joint.
- March 22, 2004 at 5:11 pm #50226
  ph2t
  Participant
  Posts: 2088
  that’s makes sense, given that is where the main power links are to +VE and -VE.
  
  cheers
- March 22, 2004 at 5:23 pm #50227
  jamiekulhanek
  Participant
  Posts: 2563
  Yup, makes it easier and makes a lower resistance stack!
- March 22, 2004 at 6:27 pm #50234
  PandaBear
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  Posts: 1866
  Quote:
  
  Try making the solder on pins 1 and 3 a bit thicker, put a thin piece of wire along the pins to aid in making the solder stick and make a big fat solder joint.
  
  Use offcut legs from resistors & diodes, easier to handle than wire. 🙂
- March 22, 2004 at 6:41 pm #50237
  jamiekulhanek
  Participant
  Posts: 2563
  Quote:
  
  Quote:
  
  Try making the solder on pins 1 and 3 a bit thicker, put a thin piece of wire along the pins to aid in making the solder stick and make a big fat solder joint.
  
  Use offcut legs from resistors & diodes, easier to handle than wire. 🙂
  
  Ah tried that, but the easiest way is to use copper wire and wrap it around the FETS, do this before the fets are installed.
- March 22, 2004 at 7:29 pm #50241
  ph2t
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  Posts: 2088
  that’s a bit much though isn’t it?
- March 22, 2004 at 8:56 pm #50242
  micro_Amps
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  Posts: 1290
  Could always try using a 6 inch nail.
  :)uA
- March 22, 2004 at 9:14 pm #50244
  Aaron
  Keymaster
  Posts: 2146
  I’ve heard PCB board pins are pretty good for it.
  
  BTW I’m about to order another batch of FETs…
  
  They will be ‘cheap’ as the supplier has passed on some currency savings. Like 20% price drop….
  
  A.
  
  --
  Site Owner Guy.
- March 22, 2004 at 9:14 pm #50445
  Aaron
  Keymaster
  Posts: 2146
  I’ve heard PCB board pins are pretty good for it.
  
  BTW I’m about to order another batch of FETs…
  
  They will be ‘cheap’ as the supplier has passed on some currency savings. Like 20% price drop….
  
  A.
  
  --
  Site Owner Guy.
- March 22, 2004 at 9:33 pm #50245
  merc-blue
  Participant
  Posts: 1547
  hmm the poor guys who designed these things thinking that people will have nece freindly even races must be furious with guys like u chucking that many fets in… :D…
- March 22, 2004 at 9:33 pm #50446
  merc-blue
  Participant
  Posts: 1547
  hmm the poor guys who designed these things thinking that people will have nece freindly even races must be furious with guys like u chucking that many fets in… :D…
- March 23, 2004 at 5:09 pm #50259
  Aaron
  Keymaster
  Posts: 2146
  I can’t wait to see a Mini-Z runnign a bunch of 2000mAh NiMh AA’s with a pair of T03 MOSFETs hanging off the roof 😉
  
  --
  Site Owner Guy.
- March 23, 2004 at 5:09 pm #50460
  Aaron
  Keymaster
  Posts: 2146
  I can’t wait to see a Mini-Z runnign a bunch of 2000mAh NiMh AA’s with a pair of T03 MOSFETs hanging off the roof 😉
  
  --
  Site Owner Guy.
- March 24, 2004 at 1:46 am #50270
  ph2t
  Participant
  Posts: 2088
  Quote:
  
  My 9×2 Stack is just not good enough, my 19t motor (0.5mm) overheats the FETs, infact, the FET stack seems to only pass about 10A!!
  
  You should put a heatsink on the fets. If you look at the graphs in the datasheets for any fet you will find that the resistance of the fets increase as temperature increases. If you keep your fets cool you will ensure a low Rds(on) value for your fets…
  
  Quote:
  
  In theory, my 19t, Neo magnet, 10 degree armature, with ball bearings *should* produce the power of a Johnson 540.
  
  and how do you figure that?
  
  ph2t.
- March 24, 2004 at 1:46 am #50471
  ph2t
  Participant
  Posts: 2088
  Quote:
  
  My 9×2 Stack is just not good enough, my 19t motor (0.5mm) overheats the FETs, infact, the FET stack seems to only pass about 10A!!
  
  You should put a heatsink on the fets. If you look at the graphs in the datasheets for any fet you will find that the resistance of the fets increase as temperature increases. If you keep your fets cool you will ensure a low Rds(on) value for your fets…
  
  Quote:
  
  In theory, my 19t, Neo magnet, 10 degree armature, with ball bearings *should* produce the power of a Johnson 540.
  
  and how do you figure that?
  
  ph2t.
- March 24, 2004 at 4:28 pm #50275
  jamiekulhanek
  Participant
  Posts: 2563
  Power usage (in W) divided by 2, because brushed motors are around 50% eficient.
  
  No ROOM for a heatsink, and besides, i am very happy with the motor it has, beats most 1/10 cars even below 20t!
- March 24, 2004 at 4:28 pm #50476
  jamiekulhanek
  Participant
  Posts: 2563
  Power usage (in W) divided by 2, because brushed motors are around 50% eficient.
  
  No ROOM for a heatsink, and besides, i am very happy with the motor it has, beats most 1/10 cars even below 20t!
- May 23, 2004 at 10:40 am #51672
  Charlie Brown
  Participant
  Posts: 105
  Sorry to revive an old topic, but I just have a few questions.
  
  I fried the FETs on my Iwaver Mini-Z, and decided to remove them off the board. So, I desoldered the front, but I’m worried about the front solder pads being shorted. Also, I yanked the FETs off, which in turn, caused the drain legs to rip a nice section of traces off the board. :angry:
  
  however, the solder pads for the source and gate connections are still OK, so I’m thinking of getting a solder sucker from RadioShack, and then soldering in wires and connecting it to an external turbo setup just like neurokinetik’s at tinyrc.com
  
  So, any soldering advice?
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