Hy guys,

Hope all of you are doing ok....

I'm a newbie in mciro-electronics, alrhough I have an electronics course,
i've never worked with PICs before...

I'm trying to design an "actuator" alike circuit, wich would run a dc motor
foward or backward, depending on it's position....Kinda like the CD-Rom draw
does, or a garage door opener....

I'm guessing that to figure the current position out I would have to use
some micro-switch or optic barrier along with one or two relays to invert
the direction....

Anyone ever deone or came across something similar?....

Thanks From Portugal

Paulo Gomes

Here we go again...you must define what it is you hope to accomplish and
then determine what resources are available...first! Then you
consider what your options are in choosing the best solution.
Don't feel bad because it's human nature to pick a solution first and
understand what's really needed later. "There's never time to do it right
the first time..." You touch on THE number one pitfall that so many
engineers fall into....and one of the main reasons why projects always
seem to run over budget and can't meet the schedule.

Picking the solution to a problem before the problem is defined or
understood is a BIG mistake. "If were easy, then everybody would do it"

When you figure it all out, stepper motors or a combination of DC motor
with gear reduction mechanism & switch actuators (of which there are many
types). Simple relay logic can be used to reverse the travel.
Good luck!
Westexjoe

On Wed, 20 Jun 2007 23:31:36 +0100, Cableguy wrote:

Hy guys,

Hope all of you are doing ok....

I'm a newbie in mciro-electronics, alrhough I have an electronics course,
i've never worked with PICs before...

I'm trying to design an "actuator" alike circuit, wich would run a dc motor
foward or backward, depending on it's position....Kinda like the CD-Rom draw
does, or a garage door opener....

I'm guessing that to figure the current position out I would have to use
some micro-switch or optic barrier along with one or two relays to invert
the direction....

Anyone ever deone or came across something similar?....

Thanks From Portugal

Paulo Gomes

On Wed, 20 Jun 2007 23:31:36 +0100, "Cableguy" wrote:

Hy guys,

Hope all of you are doing ok....

I'm a newbie in mciro-electronics, alrhough I have an electronics course,
i've never worked with PICs before...

I'm trying to design an "actuator" alike circuit, wich would run a dc motor
foward or backward, depending on it's position....Kinda like the CD-Rom draw
does, or a garage door opener....

I'm guessing that to figure the current position out I would have to use
some micro-switch or optic barrier along with one or two relays to invert
the direction....

Anyone ever deone or came across something similar?....

Thanks From Portugal

Paulo Gomes


Like westexjoe puts it you need to be more specific with your needs

Do you need relative position, absolute position, variable speed,
proportional speed control, how much over/undershoot is tolerable,
what size horsepower, etc. etc.

Describing the application goes a long way to helping make good
decisions on how best to implement what you want to do.

This is a common problem and been solved lots of times, so yes,
someone has done it.
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Thanks for all of your inputs...

My project is to motorize a compartiment door activated by a single button
like "open/close".
Since DC motors are alot more inexpensive and I have afew of them around
from slot-cars, Speed is not an issue, of course the more smooth the
moviment the better,
I've tryed to buil a "relay logic" circuit but got stuck in the midle and
eventually dropped that concept...and turned to uP....I was planing to use
PicBasic since I do some Basic related programing in Windows and WIndows
Mobile enviroments....

The movements should be like this:

If on point A go to point B and stop
If on point B go to point A and stop
If in between go to point A

Position would be determine by either micro-switch or integrated IR
barriers....I dont know waht sp+pecs to search in order to choose a uP so I
was counting on Your input and experience...I figure I only need 5 I/O pins,
and the code should be that big either....

Thanks for your time...
"default" wrote in message
...
On Wed, 20 Jun 2007 23:31:36 +0100, "Cableguy" wrote:

Hy guys,

Hope all of you are doing ok....

I'm a newbie in mciro-electronics, alrhough I have an electronics course,
i've never worked with PICs before...

I'm trying to design an "actuator" alike circuit, wich would run a dc
motor
foward or backward, depending on it's position....Kinda like the CD-Rom
draw
does, or a garage door opener....

I'm guessing that to figure the current position out I would have to use
some micro-switch or optic barrier along with one or two relays to invert
the direction....

Anyone ever deone or came across something similar?....

Thanks From Portugal

Paulo Gomes


Like westexjoe puts it you need to be more specific with your needs

Do you need relative position, absolute position, variable speed,
proportional speed control, how much over/undershoot is tolerable,
what size horsepower, etc. etc.

Describing the application goes a long way to helping make good
decisions on how best to implement what you want to do.

This is a common problem and been solved lots of times, so yes,
someone has done it.
--

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On Fri, 22 Jun 2007 19:58:35 +0100, "Cableguy" wrote:

Thanks for all of your inputs...

My project is to motorize a compartiment door activated by a single button
like "open/close".
Since DC motors are alot more inexpensive and I have afew of them around
from slot-cars, Speed is not an issue, of course the more smooth the
moviment the better,
I've tryed to buil a "relay logic" circuit but got stuck in the midle and
eventually dropped that concept...and turned to uP....I was planing to use
PicBasic since I do some Basic related programing in Windows and WIndows
Mobile enviroments....

The movements should be like this:

If on point A go to point B and stop
If on point B go to point A and stop
If in between go to point A

Position would be determine by either micro-switch or integrated IR
barriers....I dont know waht sp+pecs to search in order to choose a uP so I
was counting on Your input and experience...I figure I only need 5 I/O pins,
and the code should be that big either...

Well that would be a perfect relay logic application so that's what I
would use.

What you want is simple (keep it simple). In the old days they called
it "zero seeking."

For instance you turn on a motor and it revolves a platter (opens a
valve, moves a chain, moves something) and it rotates until it reaches
a switch that turns off the motor.

That is "zero seeking." in its basic form. Windshield wiper motors
use it today so they stop at the bottom of the stroke when power is
removed.

You have two positions you want to access and a default position to
goto when it starts up in between stations. (presumably it would be
at A or B most of the time unless something outside intervened).

You are probably familiar with those single pole double throw
switches? (from electronics suppliers or hardware stores to control a
light from two locations?)

Well, in its simplest iteration you would transfer power to one or the
other limit switch and have it move the motor until that switch was
"satisfied" (actuated - normally closed then opened by the motor or
gearing) whereupon it would switch off power.

move switch to A motor goes to A then stops. Ditto B.

NO microprocessors works with AC or DC and no electronics.

Now you also want it to goto A when in between - the in between a
power failure or something physically moved it despite the motors
wanting to return it to the desired location???


The power failure senario can be done with two relays. One comes on
with applied power (assuming that's how it got between stations) and
runs to A until it energizes a second relay that stays energized
dropping the first relay out of the circuit and latching in that
state.

If, for some reason you want it to do all that and you have
over-riding clutches or can physically overpower the drive mechanism
resulting in an in-between state you could use a PICAXE
microcontroller to do that for about $3 plus $10 in cabling to program
it - then you could add delays, and have it make decisions based on
time or other inputs.

So I come back to my earlier statement; you should just tell us what
you want to do and that will determine the best way.

Don't jump into a programmable device as the first solution you try -
they offer a lot of versatility and lots of options for later change -
but if you only want to do one thing - the simplest way is often the
most reliable way and that could be the lowly relay. (no special
power supplies, no power up reset hassles, less/no interfacing
circuitry, better noise immunity, etc.)

A Programmable Controller can always be added later.


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Two thumbs up on the relay approach, quick, cheap & robust! And
actually, no electronics are really needed (darn!)...voltage spikes on
12+ automobiles can be very nasty. Any circuit using active parts (PIC
controllers included) that is used on a car's electrical system will
have to have some kind of power conditioning to insure those little PN
junctions can survive the voltage swings...day in and day out. The only
"electronic" component needed here is a 2N4004 diode, reverse biased
across that relay's coil, without it you stand a good chance of damaging
the contacts on microswitchs. As the relay coil is de-energized the
resulting back-EMF voltage spike is more than enough to either weld the
contacts together or at least cause pitting of the contacts...that fail
later. The reversed biased diode will absorb enough of the back-EMF
energy to protect the microswitchs...one less thing to worry about.

And don't forget to include a fuse, physically located as near to the V+
supply bus (or battery) as possible! Current rating on the fuse should
be slightly over the combined current draws of motor(s) and relay coils
that pass through it. Keep it as small as possible. Chemical fuses
(Poly-fuse type) work well on things like this.

Now the hard part: the mechanical design! (ha ha)
The steering mechanism off of a remote control car should have
everything you need for the movement. Remote control cars are getting
cheap enough to justify buying one for the parts. It might also have
the microswitchs as well. A lot of those car motors are already rated
for 12VDC

For the actual lid assembly, a rotating "visor" approach should be
fairly easy to do. With a movement similiar to a motorcycle helmet's
visor. Small pins can be installed in the assembly to operate the
microswitchs.
Good Luck!
WestexJoe

ehsjr wrote:
Cableguy wrote:
Default, Thank You very much for you input, with it I learned the
"Zero Seeking" term...

What I want to acomplish is a movable faceplate for a car audio system
that would Act when the power was feed to the circuit and then return
when powered off.

Like this.

car key in On position go from A to B and Stop
car key in OFF position go from B to A and stop

I havent yet startred the face plate movement design because I havent
yet decided how far the movement should go, althought taht is not
important to the circuit design...

Once again Thank you for your input...


Paulo Gomes


A single DPDT relay should do it for you.

+12 Accessory ----[Ry1]----------+-- Gnd
|
Ry1-1 / |
+12 ---+---o-o---o o---o o---+
Batt | O_Lim | | C_Lim |
| | |-' |
| | |
| o |
| | |
| [Motor] |
| | |
| o |
| | |
| ,-| | |
| | | |
+---------+ +---------+
Ry1-2

Shown in the closed position with the C_Lim (close limit) switch
open. When the car key is turned on, the accessory line goes to
+12 and the relay is energized. +12 from the battery gets to the
top of the motor through the Ry1-1 open contact and the O-Lim
(open limit) switch. (-) gets to the bottom of the motor through
the Ry1-2 open contact. The motor spins until the O-Lim switch
opens when the limit is reached. The C-Lim switch closes as soon
as the face plate moves away from the closed position.

When the key is turned off, Ry-1 de-energizes. This time, Ry1-1
_closed_ contact brings (-) to the top of the motor through the
closed C_Lim switch, and the Ry1-2 closed contact brings (+) to
the bottom of the motor. The motor spins in the opposite direction
from the previous operation, and continues spinning until the close
limit is reached, which opens the C_Lim switch. The O_Lim switch
closes as soon as the face plate moves away from the open position.

Ed

Default, Thank You very much for you input, with it I learned the "Zero
Seeking" term...

What I want to acomplish is a movable faceplate for a car audio system that
would Act when the power was feed to the circuit and then return when
powered off.

Like this.

car key in On position go from A to B and Stop
car key in OFF position go from B to A and stop

I havent yet startred the face plate movement design because I havent yet
decided how far the movement should go, althought taht is not important to
the circuit design...

Once again Thank you for your input...


Paulo Gomes

On Mon, 25 Jun 2007 20:04:32 +0100, "Cableguy" wrote:

Default, Thank You very much for you input, with it I learned the "Zero
Seeking" term...

What I want to acomplish is a movable faceplate for a car audio system that
would Act when the power was feed to the circuit and then return when
powered off.

Like this.

car key in On position go from A to B and Stop
car key in OFF position go from B to A and stop

I havent yet startred the face plate movement design because I havent yet
decided how far the movement should go, althought taht is not important to
the circuit design...

Once again Thank you for your input...


Paulo Gomes

Some car radios had a system like that back in the 70's - 80's. Turn
on the radio and the telescopic antenna would extend, turn it off and
it would retract into the fender. Used a reversing motor driving a
push pull cable. Limit switches were the only logic.

I used a similar idea to make a bank of 12 air valves for a wood pipe
organ. The idea was to simultaneously open or close 12 valves but I
didn't want to build 12 separate air valves. I used wood slide
running in a channel that had holes spaced in it to open or close the
12 air paths from the keyed air to the pipes to change the "voice." A
felt lining made it reasonably air tight - but it was hard to move.

A 120 VAC gear motor turned a disk with an offset pin/bearing to
change the rotary motion to reciprocating motion - like a crank shaft.

Limit switches on each end of the slide stopped the valve in the open
or closed position. One synergistic effect was that the slide had
high torque and slow speed at the stop positions, so it easily
overcame the start up friction when moving from a stop.

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Cableguy wrote:
Default, Thank You very much for you input, with it I learned the "Zero
Seeking" term...

What I want to acomplish is a movable faceplate for a car audio system that
would Act when the power was feed to the circuit and then return when
powered off.

Like this.

car key in On position go from A to B and Stop
car key in OFF position go from B to A and stop

I havent yet startred the face plate movement design because I havent yet
decided how far the movement should go, althought taht is not important to
the circuit design...

Once again Thank you for your input...


Paulo Gomes



A single DPDT relay should do it for you.

+12 Accessory ----[Ry1]----------+-- Gnd
|
Ry1-1 / |
+12 ---+---o-o---o o---o o---+
Batt | O_Lim | | C_Lim |
| | |-' |
| | |
| o |
| | |
| [Motor] |
| | |
| o |
| | |
| ,-| | |
| | | |
+---------+ +---------+
Ry1-2

Shown in the closed position with the C_Lim (close limit) switch
open. When the car key is turned on, the accessory line goes to
+12 and the relay is energized. +12 from the battery gets to the
top of the motor through the Ry1-1 open contact and the O-Lim
(open limit) switch. (-) gets to the bottom of the motor through
the Ry1-2 open contact. The motor spins until the O-Lim switch
opens when the limit is reached. The C-Lim switch closes as soon
as the face plate moves away from the closed position.

When the key is turned off, Ry-1 de-energizes. This time, Ry1-1
_closed_ contact brings (-) to the top of the motor through the
closed C_Lim switch, and the Ry1-2 closed contact brings (+) to
the bottom of the motor. The motor spins in the opposite direction
from the previous operation, and continues spinning until the close
limit is reached, which opens the C_Lim switch. The O_Lim switch
closes as soon as the face plate moves away from the open position.

Ed

Thank You Guys....!!!

I never expected this kind of foward help from a news group...
You guys rock!!!

I think that I willgo with the relay option, as it is cheaper for me, since
I don't even have a uP programer, and also attending to the caution notes
posted....

As far as the "mechanical design, I'm thinking on using a "blind" like
faceplate that rolls up and down...My only doubt is ...
Waht will happen if the motion is stoped by exterior interaction, like a
slider getting stuck'
What will burn first? The motor, the relay, or the fuse?

Anyway all that rest me to do is experimenting and give you guys a big THANK
YOU for all your input..
"Cableguy" wrote in message
...
Hy guys,

Hope all of you are doing ok....

I'm a newbie in mciro-electronics, alrhough I have an electronics course,
i've never worked with PICs before...

I'm trying to design an "actuator" alike circuit, wich would run a dc
motor
foward or backward, depending on it's position....Kinda like the CD-Rom
draw
does, or a garage door opener....

I'm guessing that to figure the current position out I would have to use
some micro-switch or optic barrier along with one or two relays to invert
the direction....

Anyone ever deone or came across something similar?....

Thanks From Portugal

Paulo Gomes

Cableguy wrote:
Thank You Guys....!!!

I never expected this kind of foward help from a news group...
You guys rock!!!

I think that I willgo with the relay option, as it is cheaper for me, since
I don't even have a uP programer, and also attending to the caution notes
posted....

As far as the "mechanical design, I'm thinking on using a "blind" like
faceplate that rolls up and down...My only doubt is ...
Waht will happen if the motion is stoped by exterior interaction, like a
slider getting stuck'
What will burn first? The motor, the relay, or the fuse?

Anyway all that rest me to do is experimenting and give you guys a big THANK
YOU for all your input..

Nothing is going to burn if you do it right. Read on.

You may be able to use catalog # DCM-273 from Allelectronics.
It is used to adjust the side mirror in automobiles. Another
one might be DCM-276. Since this is a small mecnaism that will
require very little force to move, and the motor you use will
need to be physically small, it won't take a lot of current,
which brings us to the protection issue you asked about.

The wiring to the circuit must be protected by a fuse, of course.
Beyond that, you may be able to protect against a jam in the
mechanism with nothing more than a resistor in series with the
motor you use. For example, DCM-276 draws only 15 mA at 13.5 volts.
A 470 ohm, 1 watt resistance would cut the voltage to the motor to
about 7 volts, and the current to a little less than 10 mA. If the
mechanism jammed, the resistor drop the voltage even more, and
would limit the current to less than 30 mA, and the motor and
circuit should be fine. What will be required to provide protection
depends upon the motor you use.

Allelectronics has a nice range of micro switches in their
"snap-action switch" category. See, for example, catalog# SMS-223.
They also have a 12V DPDT relay you could use - catalog# RLY-622.
With a low current motor no spike protection will be needed.
If you want, you can add a snubber network (.1uf in series
with 100 ohme) across the motor terminals. You do not need a
protection diode across the relay coil. If you have the physical
space, you could add both the diode and the snubber network.

Ed

On Tue, 26 Jun 2007 18:54:59 +0100, "Cableguy" wrote:

As far as the "mechanical design, I'm thinking on using a "blind" like
faceplate that rolls up and down...My only doubt is ...
Waht will happen if the motion is stoped by exterior interaction, like a
slider getting stuck'
What will burn first? The motor, the relay, or the fuse?

Use one of the "poly fuses" from Ray Chem. No moving parts and will
automatically reset when power is removed and cheap.

Picaxe microcontrollers don't require a programmer and the software is
free - you just need a serial port to program them. Total development
system is less than $10 - and they are really easy to use. PWM, A/D,
infrared demodulator, 3-5 volt operation and micropower, etc..

http://www.hippy.freeserve.co.uk/picaxenw.htm for propaganda

http://www.rev-ed.co.uk/picaxe/ home page
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