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40702Re: Need suggestions for a motor control chip

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  • yellowlaser
    Oct 1, 2009
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      Update:

      I managed to get something working last night. Turns out I had three cascading problems that prevented the transistor/FET method from working.

      I controlled a 2n2222 transistor from the micro. The 2n2222 switched the raw system voltage (~9 volts) used to control the gate of the FET. This was enough voltage to turn on the FET. Works well at 20KHz.

      I still do not like the solution due to the extra parts and would still love a suggestion for a good part.

      -Skye Sweeney

      --- In SeattleRobotics@yahoogroups.com, FLL-Freak <fll-freak@...> wrote:
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      > I am interested in controlling a 5 volt 1 amp  DC brushed motor using 3.3V logic. I would like speed control via PWM but do not need to reverse direction. I am thinking a full h-bridge is an overkill. A simple FET/switch/ 'thing' must exist to do this!
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      > I have been playing with varius MOSFETS and found that they need more than the 3.3 volts I have from the micro to turn them on. I have a tube of IRLD024 logic level FETS, but they are 5 volt logic not 3.3. I can't seem to find a similar part for 3.3 volt logic.
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      > I tried using an NPN transister to switch a higher control voltage to the FET, but for whatever reason that does not seem to work. It also increases the part count considerably.
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      > I have tried some Avago solid state relays such as the ASSR-1511 but found the switching speed is very limited (about 2K Hz). I would at least like to modulate the motor outside of hearing range (> 18KHz).
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      > I have done a fair amount of poking around, but can't find the right key words to find a suitable part. Any suggestions would be most welcome.
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      > -Skye Sweeney
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