Searching \ for 'car window project' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=car+window+project
Search entire site for: 'car window project'.

Truncated match.
PICList Thread
'car window project'
1999\07\15@051729 by Peter Marinsek

flavicon
face
Hello,

I'm currently working in a car project where I want to drive opening and
closing car windows (car alarm).
And the question is:
a simple circuit to detect when a DC motor is overloaded (when the
window full close or full open the motor current increase)

Thanks, Peter

1999\07\15@054300 by Michael Rigby-Jones

flavicon
face
               R
>From 12v _____/\/\/\____________ To windows
          |__              |
             \>|           |
               |--/\/\/\---+
              /|    4k7
             |
             |

           To PIC (needs dropping to 5v for PIC)

This is a classic overcurrent detection scheme.  If you can't recogize the
hideous ascii art, the transistor is a PNP device.  Resistor R is chosen so
that at the current you want to detect, the voltage drop across it is enough
to switch on the transistor, say about 0.6 volts.  The other resistor is to
limit the current through the base/emitter junction.

So for 10 Amps this would give 0.6/10 =0.06 ohms.  Not a very easilly
obtainable value!  But to achieve this kind of resistance you can experiment
with a small coil of copper wire, you won't need much.  Some commercial
designs use a PCB track as the curent sense resistor.

Note that is circuit is not a precision design, the current at which it
activates will vary a bit with temperature etc, but it should be OK just for
detecting a stalling motor.

Regards

Mike Rigby-Jones

> {Original Message removed}

1999\07\15@104257 by Chris Eddy

flavicon
face
Peter;
Be wary of closing the window automatically.  The reason that the electric
windows have a 'auto down' feature but not an 'auto up' feature relates to
children's arms and heads.

Chris

Peter Marinsek wrote:

> Hello,
>
> I'm currently working in a car project where I want to drive opening and
> closing car windows (car alarm).
> And the question is:
> a simple circuit to detect when a DC motor is overloaded (when the
> window full close or full open the motor current increase)
>
> Thanks, Peter

1999\07\15@111417 by Michael Rigby-Jones

flavicon
face
Lot's of cars have auto up, at least here in the UK, and many car alarm
systems (such as Clifford) have a "total closure" option so that arming the
vehicle will close all windows/sunroof and lock all doors etc.

But you are correct, the window motors are very powerfull, and capable of
inflicting quite nasty injuries.  I suspect proper systems don't just have a
specific switch off current, but also look for a fixed increase in current
which would make the system far more sensitive.

However, hopefully you wouldn't be leaving children in the car when you are
leaving it long enough to justify arming the alarm.

Cheers

Mike Rigby-Jones

> {Original Message removed}

1999\07\15@111800 by Dave VanHorn

flavicon
face
> However, hopefully you wouldn't be leaving children in the car when you
are
> leaving it long enough to justify arming the alarm.

Never underestimate children.
I once saw a kid "riding" the window up and down while another pushed the
buttons.

1999\07\15@162415 by Richard Martin

picon face
>From my (mostly 1990 and earlier car power window experince)
the window motors are on their own fuse. I would hang a reasonably
sensitive voltmeter across the fuse and see what I read when the motor
stalled. Note: Several months back there was some discussion
(no data) about why this wouldn't work.

Car fuses tend to run .010 to .050 ohms. If this works you could
clone the fuse to be a current sensor and save mucking with existing
wiring harnesses. IF the fuse works for this, the test voltage
is an offset from 12V (or the battery voltage) which causes some
processing problems, but the ground connection on many
on board motors is though the motor mounts or a 'local' in door
connection and has it's own interconnect problems. The trick
I would try is a 'current mirror' across the fuse using DIP transistors
(for Vbe matching) to reflect the signal to being near ground for
the PIC or whatever.  An opamp isn't much more expensive but
may have problems in single rail ~12v operations. Some assembly.....

Leaving children unattended in cars is highly unsafe and therefore
ILLEGAL most places I know.

R.Martin


Peter Marinsek wrote:

> Hello,
>
> I'm currently working in a car project where I want to drive opening and
> closing car windows (car alarm).
> And the question is:
> a simple circuit to detect when a DC motor is overloaded (when the
> window full close or full open the motor current increase)
>
> Thanks, Peter

1999\07\15@165653 by l.allen

picon face
> Car fuses tend to run .010 to .050 ohms. If this works you could
> clone the fuse to be a current sensor and save mucking with existing
> wiring harnesses. IF the fuse works for this, the test voltage
> is an offset from 12V (or the battery voltage) which causes some
> processing problems, but the ground connection on many
> on board motors is though the motor mounts or a 'local' in door
> connection and has it's own interconnect problems. The trick
> I would try is a 'current mirror' across the fuse using DIP transistors
> (for Vbe matching) to reflect the signal to being near ground for
> the PIC or whatever.  An opamp isn't much more expensive but
> may have problems in single rail ~12v operations. Some assembly.....
>
This application is ideal for the MAX472 "Precision, High Side
Current Sense Amplifier.
Typical sense resistor at 10 Amps is 0.005 ohms
It is single supply (even though current can flow in either direction
through the sense resistor... a charge/discharge logic level pin
changes state, that's all.)
Check it out at http://www.maxim-ic.com

I use this I.C. in our smart battery development.
Lance Allen
Uni of Auckland
New Zealand

1999\07\15@170522 by Anne Ogborn

flavicon
face
Peter Marinsek wrote:
>
> Hello,
>
> I'm currently working in a car project where I want to drive opening and
> closing car windows (car alarm).
> And the question is:
> a simple circuit to detect when a DC motor is overloaded (when the
> window full close or full open the motor current increase)
>
> Thanks, Peter

When the motor stops rotating it'll stop making back EMF and
the voltage across it will drop. You can use an op amp as a comparator.

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\15@172638 by Wagner Lipnharski

picon face
Measuring current or voltage drop over the motors can works, but it
changes so much from different brands, contacts resistances and so one,
even some extra drags on the windows can sometimes reach the same
current of the end-of-curse.

Actually when the motor reaches the end-of-curse position, it (most of
the times) enter in a steady condition of non movement, with a (almost)
constant current or voltage drop, so monitoring this situation could be
a solution.

If you could install something close to the motor, a field effect sensor
would be (probably) a solution, since the magnetic field around the
motor is changing when the motor is rotating, and somehow steady when it
is overload and blocked.

If you really can install things, do what all the manufacturers should
do long ago, install limit switches...!

--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\07\15@213532 by Sean H. Breheny

face picon face
In my car (a 98 Nissan Sentra GXE), there doesn't seem to be any detection
(electronic or mechanical) of the window being fully up or down. If you
push the switch with the engine at idle, the engine revs up ever so
slightly (I assume to provide the needed power without draining the
battery) and this happens even when you push the switch with the window
fully up.

Sean


At 05:26 PM 7/15/99 -0400, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
spam_OUTshb7TakeThisOuTspamcornell.edu ICQ #: 3329174
________________________________________________________
NetZero - We believe in a FREE Internet.  Shouldn't you?
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html

1999\07\15@215026 by Tracey DeChambeau
picon face
In a message dated 7/15/99 10:43:22 AM Eastern Daylight Time, .....ceddyKILLspamspam@spam@NB.NET
writes:

<< Peter;
Be wary of closing the window automatically.  The reason that the electric
windows have a 'auto down' feature but not an 'auto up' feature relates to
children's arms and heads.

Chris
 >>
see the new "99 Maxima, it has auto up, with current sensing capabilities,
and when you stick you head, hand, leg, etc. in it stops and goes back down a
few inches

1999\07\15@220734 by Mike Keitz

picon face
On Thu, 15 Jul 1999 11:16:03 +0100 Peter Marinsek
<petermspamKILLspamFLUX.FE.UNI-LJ.SI> writes:

>And the question is:
>a simple circuit to detect when a DC motor is overloaded (when the
>window full close or full open the motor current increase)

Use one of the wires in the circuit as a sense resistor.  Connect small
sensing leads near each end of the wire and lead them to your amplifier.
Don't inculde any of the factory connectors in the sensing wire, since
their resistance may vary.

Most cars use a self-resetting circuit breaker in the window circuit.  If
a motor is held on after it stalls, the breaker will eventually trip.
This will remove power from the window circuit for a few seconds until
the breaker resets.  Using this as a basis for automatic operation seems
like it might be hard on the motors, but if such operation is not
frequent it would be real simple to implement.  You could probably do the
whole thing in relay logic.

___________________________________________________________________
Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: dl.http://www.juno.com/dynoget/tagj.

1999\07\15@223522 by Dennis Plunkett

flavicon
face
At 21:46 15/07/99 EDT, you wrote:
>In a message dated 7/15/99 10:43:22 AM Eastern Daylight Time, .....ceddyKILLspamspam.....NB.NET
>writes:
>
><< Peter;
> Be wary of closing the window automatically.  The reason that the electric
> windows have a 'auto down' feature but not an 'auto up' feature relates to
> children's arms and heads.
>
> Chris
>  >>
>see the new "99 Maxima, it has auto up, with current sensing capabilities,
>and when you stick you head, hand, leg, etc. in it stops and goes back down a
>few inches
>
>

Yeh, get a bit of frost on the window and it spends it's time going down
each time you want it to go up!

Dennis

1999\07\15@224520 by Tracey DeChambeau

picon face
In a message dated 7/15/99 9:36:36 PM Eastern Daylight Time, EraseMEshb7spam_OUTspamTakeThisOuTCORNELL.EDU
writes:

<<  my car (a 98 Nissan Sentra GXE), there doesn't seem to be any detection
(electronic or mechanical) of the window being fully up or down. If you
push the switch with the engine at idle, the engine revs up ever so
slightly (I assume to provide the needed power without draining the
battery) and this happens even when you push the switch with the window
fully up.

Sean >>
There is a load sensing circuit in the ECM that attempts to maintain the idle
when loaded, which is the only sensing, in you model.
Tracey

1999\07\15@225353 by Wagner Lipnharski

picon face
The IBM tape drive 3420, has a glass window that opens down to the
operator insert the tape reel into the motor and then when pressing
"load" the window closes up and then the machine starts.  When closing,
the glass enters in a half inch valley on the top of the frame, the same
happens in a car window.  Right half inch below that valley, outside of
the window, there is a rubber with a tensioned steel wire inside of it,
the wire goes to a switch that actuates whenever the rubber is pressed,
even a 1/8 of inch.  The glass doesn't touch the rubber when closing, it
passes very close.  If you keep your fingers, or any other object in the
window when it is closing, the glass will compress your finger against
the rubber and the switch will reverse the window to the bottom.

This kind of hardware is impossible to do in a car since the top of the
frame is not a straight line. However a pressure sensor could feel a
small plastic tube being pressed at the interior top of the window
frame... head or arm being pressed against the tube by the glass going
up.  This plastic tube could be inside the regular window rubber
sealant.

Much more dangerous that a crazy window is when you just close the car's
door violently with your 3 years old kid's fingers at the hinge...
ouchhhh!

Who never saw or experienced this terrible situation?

Develop some door protection system and make millions.

Wagner

1999\07\15@225954 by Tracey DeChambeau

picon face
In a message dated 7/15/99 10:36:30 PM Eastern Daylight Time,
dennisspamspam_OUTRDD.NECA.NEC.COM.AU writes:

<<
>see the new "99 Maxima, it has auto up, with current sensing capabilities,
>and when you stick you head, hand, leg, etc. in it stops and goes back down
a
>few inches
>
>

Yeh, get a bit of frost on the window and it spends it's time going down
each time you want it to go up!

Dennis

 >>
Nope, it is a learning circuit, the current control circuit is based on
individual use, not a set parameter.
Tracey

1999\07\18@093441 by paulb

flavicon
face
Michael Rigby-Jones wrote:

>                 R
> >From 12v _____/\/\/\____________ To windows
>            |__              |
>               \>|           |
>                 |--/\/\/\---+
>                /|    4k7
>               |
>               |
>
>             To PIC (needs dropping to 5v for PIC)

 The problem here is that 0.6V is a fair bit to be dropping from your
motor voltage and at say, 5 Amps, dissipates 3 Watts (albeit in this
application, with a long duty cycle).

 How about:

+5V o--+-------+---+
       |       |   |
       <       <   <
   22k <   22k <   < 4k7
       <       <   <
       |       |   |
Pic o--+       |   |
       |       |   |
        \|     |   |
    NPN  |-----+   |
        v|     |   |
       /       |   |
      |        |   |
      +--------(---+
      |        |
      <         \
  47R <          v|
      <      PNP  |--+
      |          /|  |
      +---------+    |
Gnd o-+---/\/\/\-----+---o motor return
          Rsense

 Of course, by using a ground-referenced design, direct interface to 5V
is possible.  The trip voltage is set to about 50 mV, and is adjustable
by using a 100 ohm pot instead of a fixed 47 ohm.  Rsense value, and
therefore power dissipation, is one tenth of the other.

 The transistors should "track" well if chosen from complementary
series, even better thermally if mounted together or SMD (better still
if integrated!).  Their VBEs cancel and the threshold is defined as a
proportion of the 5V supply instead.

 Untried (by myself, but a standard circuit, likely to be found in
tAoE).
--
 Cheers,
       Paul B.

1999\07\19@214837 by Dmitry Kiryashov

flavicon
face
Hi Paul.

I don't understand why you using PNP transistor ?
Up to me it isn't necessary. (motor return directly
to base of NPN or trough some diode or resistor)

WBR Dmitry.

{Quote hidden}

1999\07\20@004331 by paulb

flavicon
face
Dmitry Kiryashov wrote:

> I don't understand why you using PNP transistor ?
> Up to me it isn't necessary. (motor return directly
> to base of NPN or trough some diode or resistor)

 It's based on the premise that the base-emitter junction of a
transistor carrying a certain collector current is the best analog
(match) of teh base-emitter junction of another transistor carrying the
same current (even if one is PNP and the other NPN).  That is why two
22k resistors are used.

 The same effect may in all probability be obtained by returning the
collector of the PNP to its base, and this being the case, a matching
NPN transistor could be used with its base and collector joined.  That
would turn the circuit into a typical current mirror.

+5V o--+-------+---+
       |       |   |
       <       <   <
   22k <   22k <   < 4k7
       <       <   <
       |       |   |
Pic o--+       |   |
       |       |   |
        \|     |   |
    NPN  |-----+   |
        v|     |   |
       /       |   |
      |        |   |
      +--------(---+
      |        +--+----+
      <           |    |
  47R <            \|  |
      <       NPN   |--+
      |            v|
      |           /
Gnd o-+---/\/\/\-+----o motor return
          Rsense

--
 Cheers,
       Paul B.

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...