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Simple reversible motor control circuit for curtains (drapes) - re: Simple 555 PWM

G

Gerhard v d Berg

Simple reversible motor control circuit for curtains (drapes)
(AGvdBerg 2005-05-26)

I searched for simple circuits but could not find any so I decided to
post these, as there seem to be lots of interest.

These are very simple circuits that do not require extra electronic
components such as gates, timers, transistors and smoothing capacitors
or regulators. However nothing prevents one from enhancing the circuits
by adding remote control and PWM (Pulse Width Modulation) to the
basic circuits below.

Circuit 1: Curtain (Drape) motor direction control with automatic stop

Stop1 Stop2
Open & Close can be substituted Left |<------------->| Right
for Left & Right
/ \
/<|LS1 LS2|>\
Transformer / | | \
|--------+------------| |--+-o |-+---------+-| \-+--|
|--| | | DPDT | | | | | | |
--- | | | | SW1a | | +--|>|--+ +--|<|--+ |
) | | /\+ |-(-----o /o-| | D1 (3A) D2 (3A) |
)( | / \ | | |===/ | -------+
AC )( |_/ DB \_~ | | H | o--------| | __|__
)( ~ \ 3A / | | | H=| L<-->R | / DC
\
)( \ / | | | H | o--------| C1 ===
|Motor|
) | \/- | | | |===\ | |
\_____/
--- | __ | | | +-----o \o-| | | |
|-__---(----| | SW1b | | -------+
Fuse 3A| | | | |
|-------+--------------| |-------------------------------|

(cut & paste to Notepad for fixed pitch font viewing)
All diodes should be selected to survive the motor's stall current!
The fuse should preferably be the slow blow type and rated a bit
less than the diodes.

Operation:
The Open/Close switch (SW1) (DPDT Double Pole Double Through)
selects the voltage polarity applied to the motor and thus motor
direction to open or close curtains (drapes).
If the mechanism is not at either of the limits, the Limit Switches
(LS1 & LS2) will be closed. Depending on the position of SW1 and
motor connections, the motor will turn clockwise or anti-clockwise
to open or close the curtains (drapes).

When the curtains (drapes) approach either the final open or closed
positions, an adjustable limit switch catch should open the contacts
of the appropriate limit switch (LS1 or LS2) and stop the current
flow and thus the motor and movement of the curtains (drapes).
At this point the diode across the open limit switch contacts should
be reverse biased and thus not conduct.

If the Open/Close switch (SW1) is switched in the opposite direction
the voltage polarity across the motor would be reversed and the
diode
should now conduct until curtain mechanism moves and the now open
limit switch closes again. The current will continue to flow until
the opposite limit switch is reached opens to interrupt the current
flow and stop the motor. A special switch with a Centre-OFF position
could be used for (SW1) or a separate Power ON/OFF switched (not in
the drawing) will allow the curtains (drapes) to be partly drawn.

The transformer, diodes, fuse and switches should be selected
according to the requirements of the specific motor and curtain
(drape)
mechanism. Capacitor C1 suppresses the electrical noise generated by
the motor.

For every installation the power required to move the mechanics
can be different (due to the type of curtains and friction and often
the power supplied to the motor might require some tuning.

During installation and setup the use of a Variac or light dimmer to
slowly increase the power to the circuit is highly recommended.
This allows one to verify the correct setting of the limit switches
and fine-tune the circuit (transformer) voltage. It also assists
with
the selection of the appropriate resistors for the speed-reduction
switches as the mechanism approaches the limit switches
(see circuit 2).
A transformer with extra taps just below and above the normally
required output voltage, can be quite handy, else an appropriate
dropper resistor can be employed to reduce the power to the motor
as required.

The rectified but un-smoothed AC voltage supplies a pulsating DC
voltage and current to the motor that helps to overcome friction
in the curtain drape mechanism (and assists starting) but reduces
the average voltage applied to the motor. The rectified AC voltage
pulses should also be less strenuous to switch contacts than pure
DC.


Circuit 2: Curtain (Drape) motor control with automatic stop.
The circuit also includes extra switches to reduce motor speed
just before the end-of-rail limit switch is reached.

This circuit only supplies half-wave power to the motor but
employs a simple SPDT (Single Pole Double Through) switch
for direction control. A higher voltage supply transformer is
however required to compensate.
The full-wave power supply with DPDT switch depicted in circuit 1
could however be used with the rest of the circuit.



Stop1 Slow1 FAST Slow2 Stop2
Left |<_________---------------__________>| Right
Right
--> / / \ \
D3 /<|LS1 /<|LS2 LS3|>\ LS4|>\
SW /o--|>|-| / | / | | \ | \
|--o/ +--+/ |+--+-/ |-+----------+-| \-+--+| \+---|
| o--|<|-| | | | | | | | | |
| D4 +-|>|-+ +-/\/\/-+ +-/\/\/-+ +-|<|-+ |
--- | <-- D1 R1 R2 D2 |
) | Left -------+
)( | __|__
AC )( Transformer Open & Close can be substituted | / DC \
)( for Left & Right C1 === |Motor|
) | | \_____/
) | | |
--- | -------+
| _______ Fuse 3A (see description) |
|------------|_______|-------------------------------------------|

All diodes should be selected to survive the motor's stall current.
R1 & R2 values are determined by experimentation - should be high
wattage.

These basic circuits could be used for more than curtains (drapes)
and the pulsed AC lends itself to SCR and Triac control.

Have Fun!!!!

Gerhard van den Berg

-=OOO=-
 
Gerhard said:
Simple reversible motor control circuit for curtains (drapes)

Use tf tap changing or V regging, not series r, to adjust motor speed.
Series R will greatly reduce peak torque.

This circuit will either fry the motor or pop the fuse the first time
the motor stalls. Foldback current limit would solve that.

I'd add a 3rd central position to the switch so they can be stopped in
places other than the endstops.

What about the mechanics? Any smart ideas?


NT
 
T

Terry Pinnell

Use tf tap changing or V regging, not series r, to adjust motor speed.
Series R will greatly reduce peak torque.

This circuit will either fry the motor or pop the fuse the first time
the motor stalls. Foldback current limit would solve that.

I'd add a 3rd central position to the switch so they can be stopped in
places other than the endstops.

What about the mechanics? Any smart ideas?

My curtain controller has been working fine for nearly a year now. I'd
probably change quite a few things if I built another, but FWIW here
is a photo of its mechanics:
http://www.terrypin.dial.pipex.com/Images/CurtainControlMechanics.jpg

The motor on the left is a geared type from a screwdriver, originally
powered by 2 C-type NiCads. To its right is an improvised capstan I
made from a plastic drum (I think an ex pill case), capped by soft
wood end pieces. Into the left end piece I epoxy glued the screwdriver
bit, for attachment to the motor spindle. To the right of the capstan
is a crude bearing to maintain the capstan's horizontal axis, and to
prevent the bit slipping out of the motor.

The two vertical nylon cords visible are the curtain 'pull cords'. I
thought it would help to insert the elastic you can see here, but now
I don't think this is true. I've recently removed one of the two
sections of elastic, and would remove the other if I'd left enough
cord!

The cord is secured to the capstan symmetrically, (by passing it
through a hole in the drum, and 'pinning' it inside). It's similar in
principle to the cord and drum used to tune old radios (an idea
suggested to me here, about a year ago).

The two microswitches ensure the motor stops at its two extremes. You
can just see the markings 'OS' and 'CS', meaning Open Stop and Close
Stop respectively. So, for example, when the curtain reaches its fully
open position, normally open switch 'OS' is closed, and the circuitry
removes power from the motor.

Circuit diagrams are here:
http://www.terrypin.dial.pipex.com/Images/CurtainControllerBistables.gif
http://www.terrypin.dial.pipex.com/Images/CurtainControllerRelays.gif
http://www.terrypin.dial.pipex.com/Images/CurtainControllerCharger.gif

There's a related discussion at present (about slowing down this sort
of motor while maintaining adequate torque) in the thread
Subject: Simple 555 PWM - disappointing performance
Date: Tue, 24 May 2005 23:44:06 +0100
Message-ID: <[email protected]>
 
Terry said:
[email protected] wrote:

My curtain controller has been working fine for nearly a year now. I'd
probably change quite a few things if I built another, but FWIW here
is a photo of its mechanics:
http://www.terrypin.dial.pipex.com/Images/CurtainControlMechanics.jpg

The motor on the left is a geared type from a screwdriver, originally
powered by 2 C-type NiCads. To its right is an improvised capstan I
made from a plastic drum (I think an ex pill case), capped by soft
wood end pieces. Into the left end piece I epoxy glued the screwdriver
bit, for attachment to the motor spindle. To the right of the capstan
is a crude bearing to maintain the capstan's horizontal axis, and to
prevent the bit slipping out of the motor.

The two vertical nylon cords visible are the curtain 'pull cords'. I
thought it would help to insert the elastic you can see here, but now
I don't think this is true. I've recently removed one of the two
sections of elastic, and would remove the other if I'd left enough
cord!

The cord is secured to the capstan symmetrically, (by passing it
through a hole in the drum, and 'pinning' it inside). It's similar in
principle to the cord and drum used to tune old radios (an idea
suggested to me here, about a year ago).

The two microswitches ensure the motor stops at its two extremes. You
can just see the markings 'OS' and 'CS', meaning Open Stop and Close
Stop respectively. So, for example, when the curtain reaches its fully
open position, normally open switch 'OS' is closed, and the circuitry
removes power from the motor.

Circuit diagrams are here:
http://www.terrypin.dial.pipex.com/Images/CurtainControllerBistables.gif
http://www.terrypin.dial.pipex.com/Images/CurtainControllerRelays.gif
http://www.terrypin.dial.pipex.com/Images/CurtainControllerCharger.gif

There's a related discussion at present (about slowing down this sort
of motor while maintaining adequate torque) in the thread
Subject: Simple 555 PWM - disappointing performance


nice one. I dont know where you got the time though!


NT
 
S

Si Ballenger

Simple reversible motor control circuit for curtains (drapes)
(AGvdBerg 2005-05-26)

I searched for simple circuits but could not find any so I decided to
post these, as there seem to be lots of interest.

These are very simple circuits that do not require extra electronic
components such as gates, timers, transistors and smoothing capacitors
or regulators. However nothing prevents one from enhancing the circuits
by adding remote control and PWM (Pulse Width Modulation) to the
basic circuits below.

I've got a simple reversing switch diagram at the bottom of the
below link. The other two links show some simple setups using
servos to operate the blind tilt mechanism on a cheap blind, and
a servo controlling a home thermostat. The servos are controlled
using a servo control chip operated via a web page or a scheduler
application on a computer.

http://www.geocities.com/zoomkat/switch.htm
http://www.geocities.com/zoomkat/blindtilt.htm
http://www.geocities.com/zoomkat/t-stat.htm
 
T

Terry Pinnell

Ken Moffett said:
Terry,
Where did you get the end caps for the bungy cord?

Made them! I'm a hoarder, and amongst a thousand other things saved
the disposable razors I once used, before switching to Gillette Sensor
Excel. Sawn into various lengths they come in useful for various
things:
- PCB/stripboard spacers
- Drill bit 'shorteners' (to prevent drilling too far)
- Misc connectors
etc

In this case, I drilled holes at one end to take the curtain cord, and
then secured the bungee cord at the other end with combination of
self-tappping screw and epoxy (Araldite).

But as I mentioned, I'm not sure the bungee provides a net gain. OK,
it takes up the slack so that the knots are a bit easier to get right.
But the springiness seems to reduce accuracy. I've removed one
section; may remove the other. Will report back if I see any change.
 
K

Ken Moffett

Made them! I'm a hoarder, and amongst a thousand other things saved
the disposable razors I once used, before switching to Gillette Sensor
Excel. Sawn into various lengths they come in useful for various
things:
- PCB/stripboard spacers
- Drill bit 'shorteners' (to prevent drilling too far)
- Misc connectors
etc

In this case, I drilled holes at one end to take the curtain cord, and
then secured the bungee cord at the other end with combination of
self-tappping screw and epoxy (Araldite).

But as I mentioned, I'm not sure the bungee provides a net gain. OK,
it takes up the slack so that the knots are a bit easier to get right.
But the springiness seems to reduce accuracy. I've removed one
section; may remove the other. Will report back if I see any change.

Thank!

I love it when you can find an alternate use for otherwise throw away
trash. I figured out one time that I could get perfect flanged couplings,
for attaching 1-1/4" ShopVac hose to things, from spray-paint can lids. Cut
off the outer cylinder, and cut a hole in the bottom of the inner cylinder.
Punch several holes around the flange (formerly the top of the lid). I've
used these where I needed to attach a small dust collection hose to some
jig or fixture. I wish I could find something like that for the 2-1/2"
size hoses.
 
T

Terry Pinnell

Ken Moffett said:
Thank!

I love it when you can find an alternate use for otherwise throw away
trash. I figured out one time that I could get perfect flanged couplings,
for attaching 1-1/4" ShopVac hose to things, from spray-paint can lids. Cut
off the outer cylinder, and cut a hole in the bottom of the inner cylinder.
Punch several holes around the flange (formerly the top of the lid). I've
used these where I needed to attach a small dust collection hose to some
jig or fixture. I wish I could find something like that for the 2-1/2"
size hoses.

Yes, that's a good example of the sort of improvisation I like. It's
always satisfying to find bits from different surplus items that
serendipitously fit together. In similar vein, it's good to find novel
uses for familiar materials. Electronics cases are, well, a case in
point. Tobacco tins and plastic guttering used to be some favourites
of mine a couple of decades ago, as seen here:
http://www.terrypin.dial.pipex.com/Images/Cases.jpg
 
R

Rich Grise

Made them! I'm a hoarder, and amongst a thousand other things saved
the disposable razors I once used, before switching to Gillette Sensor
Excel. Sawn into various lengths they come in useful for various
things:
- PCB/stripboard spacers
- Drill bit 'shorteners' (to prevent drilling too far)
- Misc connectors
etc

In this case, I drilled holes at one end to take the curtain cord, and
then secured the bungee cord at the other end with combination of
self-tappping screw and epoxy (Araldite).

But as I mentioned, I'm not sure the bungee provides a net gain. OK,
it takes up the slack so that the knots are a bit easier to get right.
But the springiness seems to reduce accuracy. I've removed one
section; may remove the other. Will report back if I see any change.

Take the bungee out of the cord, and mount the motor/capstan on a
plate that's on rails, or even hinged, and spring-load the plate. :)

Cheers!
Rich
 
T

Terry Pinnell

Rich Grise said:
Take the bungee out of the cord, and mount the motor/capstan on a
plate that's on rails, or even hinged, and spring-load the plate. :)

Cheers!
Rich

I was thinking of spring-mounting the entire bedroom <g>.
 
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