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Author Topic: How to convert a servo into a dc operated point motor  (Read 4915 times)

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Offline André-NL

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How to convert a servo into a dc operated point motor
« on: March 26, 2016, 01:43:52 PM »
Hi,

This is my version of a servo driven point motor.
Had this lying on a shelf for quit a while, thought i'd finish it this time.

The servos and toggle switches are very cheap these days and i think one can build a point motor like this for  £2 :thumbsup:.

The idea was to operate the servo by using only a switch and a 5v power supply.
But to do this the servo must be "hacked".
If you search for "servo hack" on Google there are more than plenty how to's.
Only the little circuit board has to be removed from the servo, the potentiometer and end stops can stay in place.
Now you have to solder two wires on the tiny motor and close the servo.

And this little diagram shows all :D the wiring.
So when the servo turns a little the limit switch stops the action and the servo can only turn in the other direction when you flip the operating switch.


Used a 5 volt powersupply but it also operates on 2,5 volt.
At 5 volts it turns quite fast but that's fine by me :).

Made this from a piece of plastic and some aluminium.
But it can be done in many ways.






Made a little video of the pointmotor in action.
https://vimeo.com/160439819

Also tried to damage it by switching it many times. But after more than 100 times fast switching it still works, i gave up :D.

André
« Last Edit: July 03, 2016, 02:46:22 PM by André-NL »

Offline busbar

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Re: How to convert a servo into a dc operated point motor
« Reply #1 on: March 26, 2016, 02:48:00 PM »
André

Thank you for that excellent and concise idea. This is such a simple system with no mention of Arduino, Raspberry Pi or even servo testers. At last something I can understand and afford. Well done!

Dave

Offline jrb

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Re: How to convert a servo into a dc operated point motor
« Reply #2 on: March 26, 2016, 05:36:22 PM »
Nice idea.

If you changed the single pole switch for a double pole, you would then have frog switching built-in too...

Offline Bealman

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Re: How to convert a servo into a dc operated point motor
« Reply #3 on: March 26, 2016, 08:16:48 PM »
A very elegant solution. Thanks for posting!  :thumbsup:
Vision over visibility. Bono, U2.

Offline MalcolmInN

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Re: How to convert a servo into a dc operated point motor
« Reply #4 on: March 26, 2016, 11:14:05 PM »
This is my version of a servo driven point motor.
Excellent work André ! Thanks.

Powerful little thing !!

Offline Bealman

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Re: How to convert a servo into a dc operated point motor
« Reply #5 on: March 26, 2016, 11:23:24 PM »
I must admit I'm surprised that it has enough grunt to click that toggle switch, but it obviously does, as the video shows.
Vision over visibility. Bono, U2.

Offline MalcolmInN

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Re: How to convert a servo into a dc operated point motor
« Reply #6 on: March 26, 2016, 11:41:42 PM »
I must admit I'm surprised that it has enough grunt to click that toggle switch, but it obviously does, as the video shows.
Me too! I had previously seen lots of microswitch cobbles,, which is why I thought that Servo Testers, 555s and Arduino/PicAxes were more 'elegant' ( good word you chose there)
Never crossed my mind that it would pull a toggle.
Cant see the vimeo on my browser ( ! ? K-meleon) so I took Andrés word for it !

Offline André-NL

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Re: How to convert a servo into a dc operated point motor
« Reply #7 on: March 28, 2016, 03:51:09 PM »
Hi all,

I am also pleased with this minimalistic design.
It still works great, again no failure after another 100 times switching using a 5 v powersupply.
The servo has more than enough power to flip the switch.

At 2,5 v the servo stalls sometimes right in the center position of the limit switch due to the lack of power / momentum.
So 5 v seems to be a reliable voltage.

Like JRB said, if you replace one of the two single pole switches for a double pole the frogs can also be polarised.

The travel distance of the servo rod can be altered by choosing another hole in the servo arm.
Here's the difference between the red and blue position.


Suggestions are still welcome :D.
Maybe i can convince myself to replace all my Seep pointmotors with this design :hmmm:.

André
« Last Edit: July 03, 2016, 02:47:15 PM by André-NL »

Offline Bealman

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Re: How to convert a servo into a dc operated point motor
« Reply #8 on: March 28, 2016, 09:28:46 PM »
Your use of the red and blue illustrates the throw difference very well, and so simple to achieve.  Brilliant!   :thumbsup:
Vision over visibility. Bono, U2.

Offline Cooper

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Re: How to convert a servo into a dc operated point motor
« Reply #9 on: March 28, 2016, 09:49:12 PM »
Solution for Haverfordeast co-acting points @PostModN66 ? Thank you Andre!

Offline André-NL

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Re: How to convert a servo into a dc operated point motor
« Reply #10 on: April 20, 2016, 04:34:03 PM »
Hi all,

Made some modifications and this is how it looks loke now.

This version has a double instead of a single pole switch so now we can also switch the frog's polarity.
And there are some screw terminals for connecting the wiring.

The new dc servo pointmotor Mk II.


Used a piece of stripboard.
Easy to modify and it's a piece of cake to measure out (just count the holes :)).


The marked holes are drilled out using a 2,5mm drill bit.


The switch needs a 6mm hole.


Used a small file the smooth out (sort of :D) the hole.


The backside with the copper stripes.


These are all the parts we need.


On the left the terminals for the 5v power supply and on the right the terminals for switching the frog.


The backside with the wires.


Did the 100 times switching test :D and again not a single failure.
I am still surprised how strong these cheap little servos are :claphappy:.

To be continued,

André
« Last Edit: July 03, 2016, 02:51:24 PM by André-NL »

Offline Bealman

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Re: How to convert a servo into a dc operated point motor
« Reply #11 on: April 20, 2016, 11:00:28 PM »
A very professional job. You're a genius, Andre!  :thumbsup: :thumbsup:
Vision over visibility. Bono, U2.

Offline Railwaygun

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Re: How to convert a servo into a dc operated point motor
« Reply #12 on: April 21, 2016, 09:38:33 AM »
Any chance of a before/ after picture of the intervals of the servo?

THERE IS A LESS SOPHISTICATED version here using external micro switch .

 http://www.rmweb.co.uk/community/index.php?/topic/96929-no-stall-servo-point-motor-servo-hack/

Nicholas Robinson
« Last Edit: April 21, 2016, 09:54:24 AM by Railwaygun »
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Offline robert shrives

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Re: How to convert a servo into a dc operated point motor
« Reply #13 on: April 21, 2016, 11:07:26 AM »
Very interesting and will be having a go! thanks
Robert

Offline André-NL

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Re: How to convert a servo into a dc operated point motor
« Reply #14 on: April 22, 2016, 08:54:07 AM »
Hi,

Bealman,
Thanks, the basic idea is of course not mine :angel:.
Just mixed some ideas together to make a design that is easy to replicate.


Nicholas,
I love to add some pictures for you but i am not really shure what you mean with "intervals of the servo".
Also saw that version on rmweb. I searched the web a few times to find some inspiration ;) for my little design.


Robert,
If you have finished one, could you please let us know if it works ok? :photospleasesign:


André

 

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