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Goatman

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  4. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    Ok i've installed this motor
    http://www1.jaycar.com.au/productView.asp?ID=YM2716&CATID=&keywords=motor&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=
    the problem is that this motor is about half as powerfull as th old one. Car goes as slow as it did before the high voltage mod.
    Where can i get a more powerfull motor. The the drivetrain is pretty low, when driving down the hill it is little faster than on flat land, so i need more RPM than i need power.

    I could get this 6V motor which does 9k rpm at 6v, so at 12V it would do 18k rpm roughly
    http://www1.jaycar.com.au/productView.asp?ID=YM2712&CATID=&keywords=motor&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

    Any suggestions?

  8. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    Here's some pics of the completed car. It's literally too fast for it's own good  ;D
    I used a rellay and a bd139. the pcb is glued with hot glue to the frame of the car.
    all the lifted pads are from the original 4 mosfets which controlled forward, and reverse. with 1 relay i can only have forward. I don't want reverse, because if i don't press reverse or forward i can't steer (remote controll problem). So i just use reverse for steering when i'm not trying to break the sound barrier  ;).

    to sum it up, this is a complete success. Thank you all for helping me out :)

    post-8810-14279142207903_thumb.jpg

    post-8810-14279142208129_thumb.jpg

  9. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    I'll just go with my best friend (bd139). never failed me. i'll connect the relay between the collector and the supply. no worries!

    At tafe (turtiary and further education) we had a few practicles on setting the offset null on 741s. 9.5/10 times out of ten they don't work. lecturers blame it on our connections. year right. all the bjt amps we build work lol.

    one time the +ve supply pin got shorted with the negative input internally inside the op-amp. (-ve and +ve inputs were grounded to set the offset null). with a 15V supply a hole got burned between the +ve supply and the -ve input. i left it on, it was so hot i could melt solder with it easily. took about 2 minuts to finally go open cct. it melted my breadboard, lol. lecturer still blamed it on my connections.  ::)

    when i was a kid my dad bought me an elecrical kit where u have all the components in a piece of cardboard with small springs as tyerminals and all u gotta do is connect up the wires like it says in the manual. It came with a dual op-amp 8 pin IC which i have taken out recenlty. the thing NEVER FAILS ME, everytime it does everything i want it to do. Sad it's only marked with 728 and that's it. i tried googling it. no-go. :(

  12. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    yea i could do that buffer idea. i could use a bd139, bd140 and a 3055. I think i'll just go with a relay tho. cheap and easy. I doubt silicone could conduct better than copper/steel connections inside the relay. Before the mosfet blew up it lost 3 or so volts across it anyways.

    Make sure you connect a reverse-bias diode across the relay's coil to arrest flyback voltage spikes.

    Is that because of the inductive nature of the motor?

    Are you an over-clocker? No wonder you use double the battery voltage for your RC car.
    My 2.93GHz Pentium 4 has its fan running very slow most of the time. When it is doing some heavy number-crunching I hear the fan speed-up a bit. If I ever hear it running faster I'll just clean-out the dust. Grin

    Hell yea, i have an athlon 3000+ (1.8GHz) at 2.6GHz which is about as fast as a 4000+. a 4000+ actually runs at 2.4Ghz but it has double the L2 cache (1024kb).

  13. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    With an NPN power transistor driving the base of a PNP output transistor, the input voltage will be much lower. Better yet is an NPN small transistor for its low input voltage and current requirement, driving a P-channel output Mosfet.

    like one of those darlington pair things minus the extra 0.7V drop? HFE=HFE1*HFE2 :D

    I was thinking thesame thing. if the HFE was say 400 i don't think i would have a problem.

    I've decided to get a relay. All i gotta do is hook up an opamp with say a gain of 20 and the output will hit supply rails no problems. I've just learned that when the 9V battery is a bit flat that 2V can drop down to just below 1V. with a gain of 20 i can't loose!. surely the 50 or so ohms outa an opamp will drive a relay. With a relay i get no losses as i would with BJTs or MOSFETs.

    AFAIK relays are quite tollerant.  The relay i'm using to turn the pumps on for my computer's water cooling is rated at 12V, it turns on at 5V  :o

  15. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    ok. turns out that unknown transisor had a terminal going to the reverse controlling mosfet which isn't there anymore (I don't intend to replace it).
    If i get rid of that transistor, the IC is outputing 2.2V (on, 0V off) when Vbatt is 8V, 2.0V (on, 0V off) when Vbatt is 16V The Ic's VCC runs off a sepparate 9V battery.
    I'm gonna measure the output resistance of that IC to see if it can run a BJT. if it can, i'll hook up a 3055 and see what happens.

  16. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    The motor is rated at 12V, I used 2x7.2V batteries. 14.4V won't hurt it.

    If i short the drain and source pins the motor will go. so no high speed switching found here.

    I need a mosfet that will turn on with 1 or so volts.

    I tried a unity gain op-amp cct + BJT. didn't work.

    I don't have a circuit to show u guys because i didn't design it.

    AFAIK, there is a 6-7V (off-on) output from an IC which goes to a transistor (totally unknown). That transistor outputs 0.3-1.2 (off-on) to where the gate of the original mosfet used to be.

  17. n-chanel enhancement mode power mosfet

    in Datasheet/Parts requests

    Posted

    I attached 2 batteries in series to my RC car, blew the power mosfet after a few days of totally insane speeds.

    I've tried to use a bjt transistor as the input voltage is about 1 volt. Didn't work. The output impendance of the car's circuit is so damn high it's not funny!

    I'm looking for an n-chanel enhancement mode power mosfet with a really high input impendance and low turn on voltage.

    or a nice little non-power mosfet that can turn a rellay on for me.

    I have tried a motorolla IRF520 nch emode mosfet but that has both a too-low input impendance and a too high imput voltage.

    any suggestions?

    I am pretty sure the mosfet i blew up is related to the NEC C4305. I can't read the number off the one i blew up because it no longer looks like a transiostor at all  :o

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