motor & PWM
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Posts: 46,084
Hello,
Can anyone tell me how I can control the speed of an 8A motor
(forward and reverse) with a BS2? I was thinking of using PWM and a
FET switch, but I couldnt find a high current FET switch anywhere,
and I couldn't think of a way for it to run in reverse. Thanks.
Can anyone tell me how I can control the speed of an 8A motor
(forward and reverse) with a BS2? I was thinking of using PWM and a
FET switch, but I couldnt find a high current FET switch anywhere,
and I couldn't think of a way for it to run in reverse. Thanks.
Comments
8 amps is a bit much for normal components, but there are some FETs
available that would do the job.
Original Message
> Can anyone tell me how I can control the speed of an 8A motor
> (forward and reverse) with a BS2? I was thinking of using PWM and a
> FET switch, but I couldnt find a high current FET switch anywhere,
> and I couldn't think of a way for it to run in reverse.
> Do you need speed control, or just forward and reverse?
>
> 8 amps is a bit much for normal components, but there are some FETs
> available that would do the job.
>
It would be nice to have both: from -100%(full reverse) to +100%(full
forward) and anywhere in between. Do you know where I could get those
kind of FETs? Thank you very much.
>--- In basicstamps@y..., Rodent <daweasel@s...> wrote:
> > Do you need speed control, or just forward and reverse?
> >
> > 8 amps is a bit much for normal components, but there are some FETs
> > available that would do the job.
> >
>
>It would be nice to have both: from -100%(full reverse) to +100%(full
>forward) and anywhere in between. Do you know where I could get those
>kind of FETs? Thank you very much.
It's not the FET that determines FWD and REV, it's how you hook them
up. To switch polarity/direction you need a single H-Bridge or a Relay
configured to switch polarity with the supply power controlled by a FET.
My FET of choice for my RC-car hobby is an NTE2395 (approx. $5.00 US)
Spec:
Continuous Drain Current = 50Amps @ 25 deg C
= 36Amps @ 100 deg C
RDSon = 0.028 Ohms
Gate Threshold Voltage = 2V Min 4V Max
http://www.nteinc.com/specs/2300to2399/pdf/nte2395.pdf
Here is an example circuit for a typical single direction
speed controller using a standard (1mS to 2mS) RC pulse.
http://www.capable.on.ca/esc.htm
Typically I configure four NTE2395's in parallel providing
an RDSon of .007 Ohms and to reverse, I simply used a relay.
The LOWER RDSon you have the "cooler" your MOSFETS will run,
and the more efficient your power transfer will be in delivering
your power directly to your motor(s).
Beau Schwabe IC Mask Designer
National Semiconductor Wired Communications Division
500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
They have a wide range of FETs, including the high amperage ones.
Although you should note (I've mentioned this recently in another
post) that when working with mosfets rated for higher amperages, and
with lower RDSon values, there is a higher gate capacitance, meaning
that it takes longer for the mosFET to turn on, thus letting it pass
through linear mode for a longer amount of time (linear mode is where
the resistance is high, and it heats up) You can use a MOSFET driver,
which will provide high enough current to turn the mosfet on quickly,
so it won't heat up as much.. I use the tc4427 (also available at
digikey).. All I do is place it between the PWM or I/O signal, and
the mosfet's gate.. It works really good.
~Roger~
TenFour
--- In basicstamps@y..., "Beau Schwabe" <bschwabe@a...> wrote:
> At 05:47 PM 8/21/01 +0000, you wrote:
> >--- In basicstamps@y..., Rodent <daweasel@s...> wrote:
> > > Do you need speed control, or just forward and reverse?
> > >
> > > 8 amps is a bit much for normal components, but there are some
FETs
> > > available that would do the job.
> > >
> >
> >It would be nice to have both: from -100%(full reverse) to +100%
(full
> >forward) and anywhere in between. Do you know where I could get
those
> >kind of FETs? Thank you very much.
>
> It's not the FET that determines FWD and REV, it's how you hook them
> up. To switch polarity/direction you need a single H-Bridge or a
Relay
> configured to switch polarity with the supply power controlled by a
FET.
>
> My FET of choice for my RC-car hobby is an NTE2395 (approx. $5.00
US)
>
> Spec:
> Continuous Drain Current = 50Amps @ 25 deg C
> = 36Amps @ 100 deg C
>
> RDSon = 0.028 Ohms
> Gate Threshold Voltage = 2V Min 4V Max
> http://www.nteinc.com/specs/2300to2399/pdf/nte2395.pdf
>
>
> Here is an example circuit for a typical single direction
> speed controller using a standard (1mS to 2mS) RC pulse.
> http://www.capable.on.ca/esc.htm
>
>
> Typically I configure four NTE2395's in parallel providing
> an RDSon of .007 Ohms and to reverse, I simply used a relay.
>
> The LOWER RDSon you have the "cooler" your MOSFETS will run,
> and the more efficient your power transfer will be in delivering
> your power directly to your motor(s).
>
>
>
>
>
>
>
> Beau Schwabe IC Mask Designer
> National Semiconductor Wired Communications Division
> 500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
>
Original Message
From: Beau Schwabe <bschwabe@a...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, August 21, 2001 6:30 PM
Subject: Re: [noparse][[/noparse]basicstamps] Re: motor & PWM
> At 05:47 PM 8/21/01 +0000, you wrote:
> >--- In basicstamps@y..., Rodent <daweasel@s...> wrote:
> > > Do you need speed control, or just forward and reverse?
> > >
> > > 8 amps is a bit much for normal components, but there are some FETs
> > > available that would do the job.
> > >
> >
> >It would be nice to have both: from -100%(full reverse) to +100%(full
> >forward) and anywhere in between. Do you know where I could get those
> >kind of FETs? Thank you very much.
>
> It's not the FET that determines FWD and REV, it's how you hook them
> up. To switch polarity/direction you need a single H-Bridge or a Relay
> configured to switch polarity with the supply power controlled by a FET.
>
> My FET of choice for my RC-car hobby is an NTE2395 (approx. $5.00 US)
>
> Spec:
> Continuous Drain Current = 50Amps @ 25 deg C
> = 36Amps @ 100 deg C
>
> RDSon = 0.028 Ohms
> Gate Threshold Voltage = 2V Min 4V Max
> http://www.nteinc.com/specs/2300to2399/pdf/nte2395.pdf
>
>
> Here is an example circuit for a typical single direction
> speed controller using a standard (1mS to 2mS) RC pulse.
> http://www.capable.on.ca/esc.htm
>
>
> Typically I configure four NTE2395's in parallel providing
> an RDSon of .007 Ohms and to reverse, I simply used a relay.
>
> The LOWER RDSon you have the "cooler" your MOSFETS will run,
> and the more efficient your power transfer will be in delivering
> your power directly to your motor(s).
>
>
>
>
>
>
>
> Beau Schwabe IC Mask Designer
> National Semiconductor Wired Communications Division
> 500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
>
>
>
>
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