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Topic: homemade servo question (Read 2884 times) previous topic - next topic

a potentiometer has 3 wires, an electric motor has 2 wires, to make a servo you need to put them together.
a standard servo has 4 wires.
the arduino servo library can interface with a servo with out a problem.

how do i wire the potentiometer and the electric motor together to get the 4 wires i need out of the setup?

AWOL

Quote
a standard servo has 4 wires

Mine have just three.
Have I been short-changed?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Riva


a potentiometer has 3 wires, an electric motor has 2 wires, to make a servo you need to put them together.
a standard servo has 4 wires.
the arduino servo library can interface with a servo with out a problem.

how do i wire the potentiometer and the electric motor together to get the 4 wires i need out of the setup?

Afraid it's not that simple, the servo also contains something like a tiny microcontroller to convert the servo position pulses coming from the sender (arduino servo library) into a resistance value it must match on the potentiometer that is connected to the output shaft. It turns the motor forward or backward until potentiometer value matches target value.

AWOL

The electronics are unlikely to be a microcontroller in anything but the more expensive servos, but yes, there's more to it than a pot, some gears and a motor.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Erni

#4
Dec 03, 2012, 01:20 pm Last Edit: Dec 03, 2012, 01:31 pm by Erni Reason: 1
If you open a cheap analog rc servo, you will most likely find that it use a specialized chip.
In one of my servo's i found the M51660.

In the datasheet you can find a schematic like this:



Here's how servo work

http://pcbheaven.com/wikipages/How_RC_Servos_Works/

#5
Dec 03, 2012, 06:53 pm Last Edit: Dec 03, 2012, 06:56 pm by shaneshuford Reason: 1
your right, 3 wires. not 4.

thanks for the link. great read!
i googled like crazy trying to find custom homemade servos, and could only find people do little hacks where they wired a new motor up to an existing servo they took apart.

i took apart a cheap 9g servo i had and found that there is more to it than the motor and pot. i'm willing to invest the funds into the parts needed, and can custom make the gears, and poly cast my own case.

the chip in my servo has 16 pins. any idea what it could be? the servo is 9g so its super small.

#6
Dec 03, 2012, 07:11 pm Last Edit: Dec 03, 2012, 07:14 pm by shaneshuford Reason: 1
Ok i think its this one: KC5188

here is someones blog post taking apart the exact same servo:
http://wardyprojects.blogspot.com/2011/03/miniature-servo-teardown.html

Erni

#7
Dec 03, 2012, 07:19 pm Last Edit: Dec 03, 2012, 07:22 pm by Erni Reason: 1
You could take a look at the OpenServo Project.

http://www.openservo.com/StepByStep

Another possibility is to use a common H-bridge for the motor, a pot connected to the shaft, and do the rest in softare on your Arduino
Like this:
http://letsmakerobots.com/node/1524

Ore use a stepper motor and this:

https://store.cunningturtle.com/product/ct-60

i found this, after translating it to English it is very interesting.
i want to make the board custom as well though.

http://www.wettringer-modellbauforum.de/forum/index.php?page=Thread&threadID=34803

what i'm trying to do is make a very very very small servo.



Ore use a stepper motor and this:

https://store.cunningturtle.com/product/ct-60


does this need a speed controller?
this is a good idea, any idea how one would build this on their own?
again, i can purchase the parts, etch my own pcb, etc.

https://www.sparkfun.com/products/10267
seems great

BLAMO! lol
http://www.youtube.com/watch?v=byKmTMP5imc

ULN2003 $0.45 part, to drive a stepper motor?!
anyone have detailed wiring for the arduino?
and will this ULN2003 chip work with the arduino stepper library?

how sexy is this?
http://www.betasix.net/wp-content/uploads/2011/02/stepper.jpg

will the arduino stepper library work with it?

sbright33

See my library here:
http://arduino.cc/forum/index.php/topic,85335.0.html

It's on Gist and will be updated if there are any requests or bugs.
If you fall... I'll be there for you!
-Floor

Skype Brighteyes3333
(262) 696-9619

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