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'[EE] Mosfet Drivers'
2005\01\06@045801 by Lee McLaren

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Hi,

I am making a controller for the gate to my property, I am looking at
using some IRF540's to drive the motor in maybe a H bridge of half
bridge with relay, I am looking for suggestions as to what types of
devices can be used to drive the gates of the Mosfets, I will be using a
PIC  18F4550 to create the signals and it already has the appropriate
PWM and deadband correction etc so I am looking for a 'dumb' solution
that provides the appropriate drive to the gate of the mosfet. I think I
may also require some way of creating additional voltage for the high
side mosfet, this is a bit new to me so I am looking for suggestions!


regards


Lee McLaren

2005\01\06@060038 by Wouter van Ooijen

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> I am making a controller for the gate to my property, I am looking at
> using some IRF540's to drive the motor in maybe a H bridge of half
> bridge with relay, I am looking for suggestions as to what types of
> devices can be used to drive the gates of the Mosfets, I will
> be using a
> PIC  18F4550 to create the signals and it already has the appropriate
> PWM and deadband correction etc so I am looking for a 'dumb' solution
> that provides the appropriate drive to the gate of the
> mosfet. I think I
> may also require some way of creating additional voltage for the high
> side mosfet, this is a bit new to me so I am looking for suggestions!

I sell the IR2110 (http://www.voti.nl/shop/p/IC-IR2110-DIP.html) which
is a MOSFET bridge driver. Start reading the datasheet of this chip!

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\01\06@062222 by Lee Jones

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> I am making a controller for the gate to my property, I am looking at
> using some IRF540's to drive the motor in maybe a H bridge of half
> bridge with relay, I am looking for suggestions as to what types of
> devices can be used to drive the gates of the Mosfets, I will be using a
> PIC  18F4550 to create the signals and it already has the appropriate
> PWM and deadband correction etc so I am looking for a 'dumb' solution
> that provides the appropriate drive to the gate of the mosfet.

PWM strikes me as odd in this application.  Usually, it is used
to control speed of a motor.

How big a gate?  Human or vehicle?  In either cae, I would assume
that the motor and gearing would be chosen to drive the gate open
or closed at the desired rate.  Control element should drive the
motor at continuous, full voltage in one direction or the other.
All of the gate mechanisms I can recall seeing control speed via
appropriate gear reduction (or lever arm ratios) in the actuator.

If you're considering PWM to soft-start the gate's motion, there
may be considerable break-away friction that has to be overcome
before it will start moving.  That would be a poor time to have
less than full motor power acting on the gate.  Inclement weather
may significantly increase the friction or weight (i.e. a water
soaked wooden gate).  Of course, a lot depends on the mass/size
of the gate you are motivating.

PWM may be appropriate to soft-stop the gate, again depending on
the weight, support method (hinging or rolling), etc.

                                               Lee Jones

2005\01\06@074219 by Bob Ammerman

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If this is going to REVERSE-OFF-FORWARD control, rather than requiring some
sort of PWM I would recommend the very simple solution of two relays:

1: A DPDT relay wired as a reversing switch.
2: A SPST relay as a power switch.

Very simple, and with the right choice of relays, very robust.

Bob Ammerman
RAm Systems

{Original Message removed}

2005\01\06@164920 by Robert Rolf

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And if you use SPDT with the off postition shorting the motor,
you prevent coasting, and make it harder for someone to hotwire
the gate by just clip leading to the terminals.
R


Bob Ammerman wrote:

{Quote hidden}

> {Original Message removed}

2005\01\06@222616 by David P Harris

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You'll have gotten some good advice re using relays etc.

However, here's a neat solution for driving an H-bridge at 10 kHz using
a CD40106 and some transistors at 12V.  It is for model train use, but
might be of use to others.
<http://www.merg.org.uk/resources/BC1asch_e.pdf>

David


Lee McLaren wrote:

{Quote hidden}

2005\01\07@024417 by Lee McLaren

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Thanks for the advise everyone,

I like the look of the IR2110 as I need to drive a high side fet for
braking and the example from David with the CD40106 looks interesting too.

The gate is for vehicles and weighs more that a 100Kg and is over 6m in
length but only 4m goes over the driveway and the rest is used to
support the gate. It slides open but has no support across the road
(dirt road so changes a lot) so is made very rigid.
I want to open and close the gate in about 5sec and as you can imagine I
don't want it hitting the stops (or anyone!) at either end at full speed
as I will damage or break something. The motor I am driving it with is
24v 250W geared to 400 rpm and I may be looking at currents around 30A
if it stalls so I am interested in the high tech approach as well as the
learning and fun aspects as well. It also gets wet and cold here in
winter and thats when I need it to work the most as well as the changing
loads with ice and snow on the gate. I intend to use PWM to control
speed and some of the Microchip code examples for the 18 series as a
starting point.

regards

Lee McLaren


David P Harris wrote:

{Quote hidden}

2005\01\07@071010 by Mike Hawkshaw

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Talking of shorting things out, it is common practice to use mechanically
and electrically interlocked relays to avoid accidents on the mains
side.....

Mike.

{Original Message removed}

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