Looking for Encoders

[Ralph Gnauck]

 

Can someone point me to a good source for wheel encoders,

 

I would prefer enclosed type not open disks.

 

I have a base with motors and wheels already, the axle shafts are 1/4 inch with no back shaft so the encoder would need to sit on the shaft between the motor and the wheel, i.e. open hole type fitting.

 

Need about 400-500 ppr.  max RPM about 200.

 

Found these  @ digikey, they look ideal but a bit expensive,

 

http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=us&keywords=AMT102-V

 

 

Anyone have any other suggestions please.

 

 

Ralph

[Ted Larson]

 

Bob and I have used these on many projects.  They are available from 400-1440 ppr.

http://www.usdigital.com/products/encoders/incremental/rotary/kit/e4p/

 

You can’t tell from the photo, but there is an ordering option with a hole in the cover so you can have the shaft run through the encoder completely, which is what it sounds like you need.

They are $25 each, and super accurate.

 

Hope this helps,

 

-Ted

[Balaji Lakshmanan]

http://www.autonics.com/ 

I use these encoders. They are easy to interface and come in many different sizes and PPRs. 

-- 
Cheers
Balaji Lakshmanan
+91-9840836275
http://www.balajil.com
http://www.twitter.com/balajil

"It is not who we are but what we Dream and Do that defines us"

[Wayne C. Gramlich]

All:

I use the US Digital encoders as well.

I keep hoping that somebody will develop a board that uses
one of the nifty Hall Effect rotary sensors. These folks make
some:

<http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders/Rotary-Encoders>

and there are others.

-Wayne

Ted Larson wrote:
>
>
> Bob and I have used these on many projects. They are available from
> 400-1440 ppr.
>
> http://www.usdigital.com/products/encoders/incremental/rotary/kit/e4p/
>
> You can’t tell from the photo, but there is an ordering option with a
> hole in the cover so you can have the shaft run through the encoder
> completely, which is what it sounds like you need.
>
> They are $25 each, and super accurate.

[much snippage]

[Dennis Burke]

Due to the 1/4" shaft you'll want the ones from Digi-Key.

[Alan Marconett]

Wayne,

We use the Austria Microsystems encoders at work and have interfaces.
Interested?

Alan KM6VV

> -----Original Message-----
> On Behalf Of Wayne C. Gramlich

[Wayne C. Gramlich]

Alan:

Somehow, I do not think that Di Vinci is going to repackage
their Hall effect encoders for the hobbyist market.

What I keep hoping is that somebody will design a board and
some magnets that can be attached to multiple different shaft
diameters *and* be cheaper than a US Digital E4. This may be
wishful thinking on my part, but I can hope.

-Wayne

Alan Marconett wrote:
> Wayne,
>
> We use the Austria Microsystems encoders at work and have interfaces.
> Interested?

[snippage]

[Ralph Gnauck]

Wayne,

 

Is this the sort of thing you are looking for.

 

Solarbotics has a board designed to retrofit to their GM17 motors but it looks like it could be addapted to other motors as well.

 

http://www.solarbotics.com/products/51510/

 

Thanks everyone for the other advice, I will look at the other options to see what will work best.

 

 

Ralph

 

---

From: Wayne C. Gramlich <wa...@gramlich.net>
To: hbrob...@googlegroups.com
Sent: Tue, November 3, 2009 9:59:20 AM

Subject: [HBRobotics] Re: Looking for Encoders

[Alan Marconett]

No they aren't interested.

I think da Vinci is dead. No, Intuitive Surgical wouldn't be interested
either!

I thought perhaps you were interested in the logic used. I momentarily
considered them, but never received samples (I do have some parts, 'tho).

Alan KM6VV

> -----Original Message-----
> On Behalf Of Wayne C. Gramlich
>

[don clay]

I'm curious. How do you effectively make use of Hall Effect Switches?

I have attempted to use them a few times, but every time there are glitches of
the variable kind on the edges.

I've seen others have the same result, but they're still around so someone seems
to be having success with them.

I've gone to optical switches almost exclusively as a result.

[Alan Marconett]

Hall Effect switches don't generally glitch much, they have hysteresis.

We were talking about rotary encoders,

http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders/Rotary-Enc
oders

These are "analog", ratio metric between two analog readings of the magnet's
flux from two directions, 90 degrees or in "quadrature".

Alan KM6VV

> -----Original Message-----
> On Behalf Of don clay

[don clay]

That's not been my experience to date.

[Albert B. Margolis]

Here is a home made design:

http://hades.mech.northwestern.edu/index.php/Adding_a_magnetic_encoder_to_a_GM3_Gearmotor

I talked to the professor who posted this a few years ago. One thing I
learned is that if you go to a place like amazingmagnets.com you can
find magnets with the poles aligned in several different ways relative
to the shape of the magnet. That lets you arrange to get a nice clear
magnetic pulse that you might not get with a randomly chosen magnet.

When shopping for hall effect sensors you will find both digital and
analog output sensors. With the analog sensors you can tune the
circuit to trigger just at the point of maximum field intensity. With
the digital switches you might have an "on" state long enough to
occasionally miss a reversal of direction, but its hard to imagine
that happening enough to be a serious problem.

Its crossed my mind to make a kit of these parts but it hasn't happened yet.

-- Al Margolis
founder, www.HobbyEngineering.com

[Nathaniel Lewis]

That looks good for building cheap robots with odometry!  Anyone thinking an inexpensive way to do floorbot?

[Randy M. Dumse]

Yes! That has to be the cheapest, most mountable, encoded motor combo I've seen.

 

I'm thinking if we should rethink our Mini-Sumos we use in the Digital Electronics and Robotics course I created at UNI. Instead of a modified RC Servo at ~$16 we could do full DC Servo motor control for ~$17 a unit. The PlugaPod(TM) I use already has PWM outputs and quadrature inputs, so I am very excited about the possible switch over.

 

Wish we had some specs on the torque/speed of the motor unit, how it compares to RC Servos.

 

Notice also they sell gear ratio kits to trade speed/torque by factors of 2. Very attractive.

 

Randy

---

From: hbrob...@googlegroups.com [mailto:hbrob...@googlegroups.com] On Behalf Of Nathaniel Lewis
Sent: Tuesday, November 03, 2009 3:37 PM

To: hbrob...@googlegroups.com
Subject: [HBRobotics] Re: Looking for Encoders

[Jim McBride]

free shipping to boot....

http://www.dealextreme.com/

[Camp Peavy]

> I have attempted to use them a few times, but every time there are glitches of the variable kind on the edges.

A Schmitt trigger can be used to clean up those waveforms.   Camp

[Wayne C. Gramlich]

Ralph:

Here is a quick dump on encoders:

1) In general, the more ticks per wheel revolution the better,

2) but more ticks per revolution, can overwhelm a microcontroller
that is trying to keep track of it all via interrupts, so

3) look for a microcontroller with built in quadrature encoder
hardware support, or

4) use a chip dedicated to the task like the LS7366 (a stand-alone
quadrature encoder chip with an SPI interface.) The LS7366
is extremely hard to come by (I get mine from an outfit in
NY called Gemini electronics; not fun.)

Encoders can be put directly on the wheels, or on the motors
themselves. Putting them on the motors tends to be be harder,
since most vendors do not sell motors with an extra shaft out
the back. So far, I've found the following vendors sell motors
with back shafts -- Lynxmotion, Super Droid, Solutions-Cubed,
and (new) Parallax. I'm sure there are others.

I almost always use US Digital E4 encoders; they are relatively
inexpensive and can be adapted to a large number of motor
shafts. They have a large number options, so order carefully.

It is annoying, but by the time I have finished buying the
motors, H-bridges, encoders, encoder electronics, wheels,
hubs, motor mounts and everything, I have typically burned
through $100 per motor. This feels wrong, but it is very typical.
Furthermore, there is usually some kludge required to bolt the
motors to the wheels, or encoder to the motor or some such nonsense.

Right now, my preferred motor/wheel vendor is BaneBots. There
web site is a bit confusing, but they sell nice wheels with a
nice range of sizes, nice hubs that can be used to gang up to
3 wheels per hub, motors with long shafts, bearing mounts to
provide additional shaft support, a large selection of motor
sizes and gear ratios, etc. The place where they miss is they do
not sell motors with back shafts (yet.) My solution is to
buy a compatible motor with a back shaft, install the appropriate
pinion gear and replace the motor. A standard US Digital
encoder is used and it feeds an LS7366 quadrature encoder
chip. The result is quite nice, but not particularly cheap.

-Wayne

[Nathaniel Lewis]

That motor is also compatible with their GM series wheel right?  It seems to have the same connector, but they do not say whether it is nor is not.

                                                                                                                                                Nathaniel