12Vdc Solenoid Driver Circuit requ'd.

[PT]

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried crudely
PWM but it is a bit stuttery.

Thanks for any help,
Pete.

 

[petrus bitbyter]

"PT" <PT@lisome.com> schreef in bericht
news:vkO8d.16094$5O5.5031@news-server.bigpond.net.au...

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried
crudely
PWM but it is a bit stuttery.

Thanks for any help,
Pete.

The solenoids I know are not meant to make controlled moves other then "on"
anf "off". For controlled moves, components like stepper motors, servos or
even voice coils are used.

petrus bitbyter


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.771 / Virus Database: 518 - Release Date: 28-9-2004

 

[Frithiof Andreas Jensen]

"PT" <PT@lisome.com> wrote in message
news:vkO8d.16094$5O5.5031@news-server.bigpond.net.au...

The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

That's really hard to do without all sorts of complexity - the
force/displacement characteristics is very nonlinear and position control
would be hard.
You would be better off using f.ex. a door actuator for the central locking
in cars which will do what you want out of the box. If the slow movement is
to maintain silence, "muscle-wires" are cool too. Maybe a pneumatic actuator
supplied with air compressed by the solenoid?

 

[Terry Pinnell]

"PT" <PT@lisome.com> wrote:

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried crudely
PWM but it is a bit stuttery.

I'm curious about your reasons for wanting to do it? For slow motion,
how about a geared motor, either mechanically attached via a lever or
cam, or winching via a pulled wire/cord, or turning a 'nut' on a
thread?

Actually I had same question a year or so ago. I had a pair of new
shoes that were pinching my toes. I improvised a contraption powered
by a very large 24V soloenoid, whose pull was converted into a
'scissor' action, stretching the appropriate part. With a full 30V it
was on the violent side. I proposed to leave it on overnight, so
played for a while with trying to calm it. Essentially in vain, for al
the reasons given by others here.

One other idea would be to use the full-speed solenoid to close a
bellows or pump of some sort, and connect an exit of that to a piston.

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Jamie]

ah.
that is a problem.
we did that once but its hard to
control the position/load.
PWM signal generating a DC pulse
works well.
it can be done because it has been done
but not with reliable pull speeds verses
load changes unless you have a movement
feed back pot of something like that.
i think a servo motor would do you much
better, one with an actuator on it.



PT wrote:

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried crudely
PWM but it is a bit stuttery.

Thanks for any help,
Pete.

 

[CBarn24050]

Subject: Re: 12Vdc Solenoid Driver Circuit requ'd.
From: Terry Pinnell terrypinDELETE@THESEdial.pipex.com
Date: 06/10/2004 16:33 GMT Standard Time
Message-id: <sa38m05e9blmduaqms5fdbbstgpmm9lchd@4ax.com

"PT" <PT@lisome.com> wrote:

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

No simple way I'm afraid. The problem is that the position of the core is load
dependent and the thrust is position dependent. You can measure the di/dt of
the pwm, which will give you the position of the core, you can use that to
control the current. Not easy but it will keep you off the streets for a while.

 

[Ken Smith]

In article <vkO8d.16094$5O5.5031@news-server.bigpond.net.au>,
PT <PT@lisome.com> wrote:

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

Just sort of thinking out loud here:

As the plunger of the solenoid moves in, the inductance increases greatly.
If a PWM chip applies a voltage to it for some short fixed amount of time,
the current will ramp up to a higher current with the plunger out than
with it in.

With only a little trickiness, a circuit can be made such that the voltage
on the solenoid reverses and puts its stored energy back onto the
input power line.

If the supply voltage is above twice the normal DC voltage for the
solenoid, the PWM chip will never need to run over 50% duty cycle and thus
we can be sure that the current stops between pulses.

For this idea to work, I think we need a PWM chip that has a fixed on time
and a variable frequency. One of the Linear "Burst mode" chips may do.

We need some sort of peak current detector. If the peak is too low, the
plunger is too far in and we need to delay the next pulse from the PWM by
some amount. Over time, we slowly lower the peak current we demand
allowing the PWM to move towards 50% duty.


I think this whole thing could be done with a PIC and a few power
components. It would be fun to try.


--
--
kensmith@rahul.net forging knowledge

 

[John Fields]

On Fri, 08 Oct 2004 07:44:44 GMT, "PT" <PT@lisome.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:57gam01homm7c6ejui0obser0nhs8670la@4ax.com...
On Thu, 07 Oct 2004 11:31:13 GMT, "PT" <PT@lisome.com> wrote:


All replies sofar have provided me with lateral thought and I thank each
and
everyone for that. My current thinking now is to continue with PWM
and/or
some form of damping such as springs and a cap. Spehro mentioned
"dashpot"
which sounds interesting.

What say?

As well, I have a maximum space consideration of 30mm in height, which is
why I have chosen this path. However I am still open to any suggestions.
The load is approx. 500g.

---
Could you say something about the physical orientation of the solenoid
and the load? That is, are they coaxial and vertical with gravity
supplying the restoring force for the load, or are they arranged in
some other way?

--
John Fields


It forms part of a product development. Solenoid orientation is
horizontal. Load is sprung which restores the plunger after a "on"
period of about 4 seconds. The need for slow motion is to add
sophistication.

---
Assuming no friction between the plunger and the bore of the solenoid,
the force the spring exerts on the solenoid plunger will be linear,
but the force the current will cause the magnetic field to exert on
the plunger will follow an inverse square law and will depend on the
location of the plunger within the solenoid and the force it must
overcome which is exerted by the spring. The game, then, will be to
determine how the current must change in order to get the plunger to
move from point a to point b in the time alloted, against the force
exerted by the spring.

--
John Fields

 

[Ken Smith]

In article <6c71b322.0410080708.208e1290@posting.google.com>,
Tom Seim <soar2morrow@yahoo.com> wrote:
[...]

I dont think your pwm method will work. Solenoids are highly
nonlinear; trying to measure this and store it in a rom is doomed to
failure because current doesnt control position of the plunger-it
controls acceleration.

Plunger position varies the inductance so there is some chance of a closed
loop solution. If you servo the inductance to follow a ramp, the punger
would have to move slowly. The tricky bit is measuring the inductance,
applying the power and closing the loop all at the same time.


--
--
kensmith@rahul.net forging knowledge

 

[Fred Bloggs]

Tom Seim wrote:

"PT" <PT@lisome.com> wrote in message news:<5O99d.17258$5O5.937@news-server.bigpond.net.au>...

"PT" <PT@lisome.com> wrote in message
news:vkO8d.16094$5O5.5031@news-server.bigpond.net.au...

Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried

crudely

PWM but it is a bit stuttery.

Thanks for any help,
Pete.




All replies sofar have provided me with lateral thought and I thank each and
everyone for that. My current thinking now is to continue with PWM and/or
some form of damping such as springs and a cap. Spehro mentioned "dashpot"
which sounds interesting.

What say?

As well, I have a maximum space consideration of 30mm in height, which is
why I have chosen this path. However I am still open to any suggestions.
The load is approx. 500g.

Cheers,
Pete.


I dont think your pwm method will work. Solenoids are highly
nonlinear; trying to measure this and store it in a rom is doomed to
failure because current doesnt control position of the plunger-it
controls acceleration. To have any hope you will need a solenoid with
a linear force/distance curve. I have seen designs in books, but not
as products you can buy.

Tom

Well- that post is just pseudo-OnT #10,000 indicating you don't know
your butt from a hole in the ground about anything electronic. Give it
up, non-technical maggot swivel chair operator senior scientist IV. Your
only skill set is making a power point presentation about your
half-assed organization that serves no purpose other than preserving itself.

 

[Rich Grise]

On Friday 08 October 2004 12:44 am, PT did deign to grace us with the
following:

"John Fields" <jfields@austininstruments.com> wrote in message
On Thu, 07 Oct 2004 11:31:13 GMT, "PT" <PT@lisome.com> wrote:
---
Could you say something about the physical orientation of the solenoid
and the load? That is, are they coaxial and vertical with gravity
supplying the restoring force for the load, or are they arranged in
some other way?


It forms part of a product development. Solenoid orientation is
horizontal. Load is sprung which restores the plunger after a "on"
period of about 4 seconds. The need for slow motion is to add
sophistication.

Then just mount a dashpot to slow down the plunger. No changes
to the electronics at all!

Good Luck!
Rich

 

[Ken Smith]

In article <qomfm01j0462706qdn3u3h9agg9883i2e3@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]

period of about 4 seconds. The need for slow motion is to add
sophistication.

Then just mount a dashpot to slow down the plunger. No changes
to the electronics at all!

I suggest a spring and dashpot. The solenoid can snap in and pull on the
spring. It is easier to get springs that repeat well.

I think 4 seconds is too long of a time.

Hardly "sophisticated"...

If you make the air leak on the hash pot just right, you might be able to
get the Startrek door opening "pshhhht" sound out of it.
--
--
kensmith@rahul.net forging knowledge

 

[John Fields]

On Sat, 9 Oct 2004 15:03:38 +0000 (UTC), kensmith@green.rahul.net (Ken
Smith) wrote:

In article <qomfm01j0462706qdn3u3h9agg9883i2e3@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]
period of about 4 seconds. The need for slow motion is to add
sophistication.

Then just mount a dashpot to slow down the plunger. No changes
to the electronics at all!

I suggest a spring and dashpot. The solenoid can snap in and pull on the
spring. It is easier to get springs that repeat well.

I think 4 seconds is too long of a time.

Hardly "sophisticated"...

If you make the air leak on the hash pot just right, you might be able to
get the Startrek door opening "pshhhht" sound out of it.

---
If you get the air leak on the hash pot just right, you may very well
hear a universe of detail in the "pshhhht" sound...

--
John Fields

 

[Rich Grise]

On Saturday 09 October 2004 08:03 am, Ken Smith did deign to grace us with
the following:

In article <qomfm01j0462706qdn3u3h9agg9883i2e3@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]
period of about 4 seconds. The need for slow motion is to add
sophistication.

Then just mount a dashpot to slow down the plunger. No changes
to the electronics at all!

I suggest a spring and dashpot. The solenoid can snap in and pull on the
spring. It is easier to get springs that repeat well.

I think 4 seconds is too long of a time.

Hardly "sophisticated"...

If you make the air leak on the hash pot just right, you might be able to
get the Startrek door opening "pshhhht" sound out of it.
--
Then you'd need something for that little "toink" at the end. ;-)

Cheers!
Rich

 

[Fred Bloggs]

Tom Seim wrote:

Fred Bloggs <nospam@nospam.com> wrote in message news:<4167740E.7020307@nospam.com>...

Tom Seim wrote:

"PT" <PT@lisome.com> wrote in message news:<5O99d.17258$5O5.937@news-server.bigpond.net.au>...


"PT" <PT@lisome.com> wrote in message
news:vkO8d.16094$5O5.5031@news-server.bigpond.net.au...


Could someone suggest/draw a simple driver circuit that would energise a
12Vdc, 500mA solenoid slowly, if that is possible. The solenoid ideally
would move about 10mm over a period of about 1 second. Initiation would be
by pressing a button.

My understanding would be some form of current control. I have tried

crudely


PWM but it is a bit stuttery.

Thanks for any help,
Pete.




All replies sofar have provided me with lateral thought and I thank each and
everyone for that. My current thinking now is to continue with PWM and/or
some form of damping such as springs and a cap. Spehro mentioned "dashpot"
which sounds interesting.

What say?

As well, I have a maximum space consideration of 30mm in height, which is
why I have chosen this path. However I am still open to any suggestions.
The load is approx. 500g.

Cheers,
Pete.


I dont think your pwm method will work. Solenoids are highly
nonlinear; trying to measure this and store it in a rom is doomed to
failure because current doesnt control position of the plunger-it
controls acceleration. To have any hope you will need a solenoid with
a linear force/distance curve. I have seen designs in books, but not
as products you can buy.

Tom

Well- that post is just pseudo-OnT #10,000 indicating you don't know
your butt from a hole in the ground about anything electronic. Give it
up, non-technical maggot swivel chair operator senior scientist IV. Your
only skill set is making a power point presentation about your
half-assed organization that serves no purpose other than preserving itself.


I guess that's why I'm employed and you're not.

You just don't 'sound' like someone who is employed. That's why you
became a 'body' for Battelle.

 

[Ken Smith]

In article <CGV9d.1385$Mh7.946@trnddc04>, Rich Grise <null@example.net> wrote:

On Saturday 09 October 2004 08:03 am, Ken Smith did deign to grace us with
the following:
[... me ..]
If you make the air leak on the hash pot just right, you might be able to
get the Startrek door opening "pshhhht" sound out of it.
--
Then you'd need something for that little "toink" at the end. ;-)

Something has to stop the travel.

or: Add a PIC and a little speaker and you can make it close "with a self
satisfied hum".


--
--
kensmith@rahul.net forging knowledge

 

[Ken Smith]

In article <6hdgm0hagnu67sjrifcopnel377ssuejem@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]

Arguably the easiest way would be to run it open-ended.

I disagree. Getting inductive elements that are accurate to 10% is hard.
Getting 1% resistors is easy. I strongly suspect that using feedback
would allow a wider range of mechanical parts.

To get the
ramping function, connect it to a power supply, crank up the voltage
until it (the plunger) moved to the starting position, then measure
the voltage

Yes but .... "crank up the current" while monitoring the voltage. The
inward motion of the plunger causes the voltage to rise abruptly. If you
digitized that curve, and applied that voltage profile, your idea may work
well enough. We are just talking about getting a "quality feel" out of
some "cheap junk" parts here. We are not launching a space probe.

--
--
kensmith@rahul.net forging knowledge

 

[Rich Grise]

On Saturday 09 October 2004 04:36 pm, Ken Smith did deign to grace us with
the following:

In article <CGV9d.1385$Mh7.946@trnddc04>, Rich Grise <null@example.net
wrote:
On Saturday 09 October 2004 08:03 am, Ken Smith did deign to grace us with
the following:
[... me ..]
If you make the air leak on the hash pot just right, you might be able
to get the Startrek door opening "pshhhht" sound out of it.
--
Then you'd need something for that little "toink" at the end. ;-)

Something has to stop the travel.

or: Add a PIC and a little speaker and you can make it close "with a self
satisfied hum".

Well, here's the files:
http://www.old-hippie.com/sound_files/pg/pgw/startrek.html

( I really like that domain name! ;-) )

Cheers!
Rich

 

[Rich Grise]

On Saturday 09 October 2004 02:39 pm, petrus bitbyter did deign to grace us
with the following:

Also the dashpot comes to my mind. Will a stroke of 10mm be enough to
build up enough pressure to reduce the speed adequately? What about cost
and maintenance? That mechanical things tend to wear out much more rapidly
then
electronics. At this point I've only questions. Leave the answers to
mechanics.

Just use one of these, and build a LIM:

http://rich_grise.tripod.com/images/Solenoid.gif

Cheers!
Rich

 

[Ken Smith]

In article <ejfim0d7uk2rg8lra8eug2msctvvatl655@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]

Unless you're using actual
physical position as as feedback, I don't think using 1% resistors
will make much difference if the characteristics of the magnetic
structure are as variable as you seem to think they are.

How about it? Have you got any data to supprt your claim?

For 1% resistors making a difference when you end up having to make the
thing self-calibrate no.

For inductors better than 10% being hard to get, consult any makers data
sheets.

For electromechanical things not repeating well I only have my hands on
experience with this.

---

To get the
ramping function, connect it to a power supply, crank up the voltage
until it (the plunger) moved to the starting position, then measure
the voltage

Yes but .... "crank up the current" while monitoring the voltage. The
inward motion of the plunger causes the voltage to rise abruptly.

---
So what? Whether you crank either the current or the voltage the
other will follow and the plunger will move. The voltage will settle
in a few milliseconds or so, and when it does and the solenoid plunger
is where you want it to be, _that's_ when you measure the voltage.

That won't work for 2 reasons.

(1) For a constant current, the force on a plunger increases as it move
into the coil. This means that when the plunger starts to move will
usually be when it snaps completely in.

(2) The moving plunger either (a) changes the current or (b) changes the
voltage, depending on which of the two you are controlling. The current
does not settle quickly at all.

--
--
kensmith@rahul.net forging knowledge