Cheap encoders

[Gdeaver]

Yes, I'm cheap and therefore always looking for cheap robot parts. Look at these 128 CPR encoders at BG Micro.
http://www.bgmicro.com/index.asp?Pag...D&ProdID=12916 Now, if the kitbot trans has an out put shaft for these, one part of the robot would be cheap and easy this year.

[Tom Line]

That price looks great, but I'm unable to find the specifications for them anywhere. Have you had any luck finding them? Operating voltage, max RPM, etc?

[Andrew Schreiber]

Tom, I found this site (http://www.electro-nc.com/products/encoders.shtml) Might be of some use but I don't have the time to really dig any more on this.

That being said, the lack of full documentation on the linked site worries me. Most reputable sites provide a little more information on their products. Also, quadrature encoders are usually MUCH more expensive which sets off another flag for me. I would be careful ordering from this site, if you do make sure you monitor your credit card well after that.

[Mark McLeod]

That encoder is for a control panel for a human to turn like a dial.
It wouldn't hold up to the rigors or rpm's of a drive train.

[Joe Ross]

These are our favorite cheap encoders: http://www.chiefdelphi.com/media/papers/1743

[billbo911]

Originally Posted by Mark McLeod

That encoder is for a control panel for a human to turn like a dial.
It wouldn't hold up to the rigors or rpm's of a drive train.

Most likely very true. But that should not prevent a team from grabbing a few of these. At $4 a piece when you purchase four or more, they are a serious bargain!!

So, what can they be used for??

Learning how to use encoders.
Prototyping designs.
Manipulators that don't beat the tar out of an encoder.
Small personal projects.
Verifying that your code behaves as you intended before you put it on the Big Bot.
etc. etc. etc.

No doubt these are not as durable as what you might get from a company like US Digital, but if care is used, they should be quite useful in many implementations, as long as you understand what you are working with and how to use it.

Besides, at this price, you can afford to make a few mistakes and not ruin a really nice encoder.

[Gdeaver]

These are not mechanical encoders. They are optical encoders. The specs, look at this link.
http://docs.bgmicro.com/pdf/oak-grigsby%20encoders.pdf
It's hard to tell from the doc if they have sleeve or ball bearings. Any way they should work for attaching to the output of a trans.

[Mark McLeod]

If they turn out to use ball bearings then I'd like them
I'm not one for sleeve bearings except in low rpm uses.

[billbo911]

Originally Posted by Mark McLeod

If they turn out to use ball bearings then I'd like them
I'm not one for sleeve bearings except in low rpm uses.

I'm with you 100% on that.

I'll let you know exactly what they are when mine arrive. I ordered 5 this morning.

I have plenty of projects that can benefit from these if they are even barely decent.

[Ivan Helmrich]

Here's a link to a catalog page. Specs are at the bottom of the page. 91 series looks to have sealed sleeve bearings rated at 300 RPM. Still a great deal for lower speed applications.

http://www.electro-nc.com/oak/p0104.pdf

[Qbranch]

My conscience would like to make a statement: Rotary encoders, pretty much the most necessary sensor in a high performance motion control system, are probably not a place you want to cut cash in your robot.

I might be wrong in this case... but if I were building a machine of some kind, I'd probably try to save money elsewhere on a less critical part... maybe buying cheaper limit switches or something else that doesn't need to be as precise... or maybe buying looser tolerance bearings if you don't need super precise shaft positioning...

That's my 0.55 Rubles.

-q

[billbo911]

Originally Posted by Qbranch

My conscience would like to make a statement: Rotary encoders, pretty much the most necessary sensor in a high performance motion control system, are probably not a place you want to cut cash in your robot.

I might be wrong in this case... but if I were building a machine of some kind, I'd probably try to save money elsewhere on a less critical part... maybe buying cheaper limit switches or something else that doesn't need to be as precise... or maybe buying looser tolerance bearings if you don't need super precise shaft positioning...

That's my 0.55 Rubles.

-q

It is a good thing these will mostly be used in my own Vex robots, or maybe a motorized recliner operated by my lil' Arduino.

I will also use them to help my programmers get familiar with encoders and their usefulness, as you mentioned. But, you are correct, when it comes to the competition robot, reliability is paramount. (Oooo, there's that word again )

[martin417]

Originally Posted by Andrew Schreiber

Tom, I found this site (http://www.electro-nc.com/products/encoders.shtml) Might be of some use but I don't have the time to really dig any more on this.

That being said, the lack of full documentation on the linked site worries me. Most reputable sites provide a little more information on their products. Also, quadrature encoders are usually MUCH more expensive which sets off another flag for me. I would be careful ordering from this site, if you do make sure you monitor your credit card well after that.

I have bought stuff from BG before. They are a surplus reseller. Someone has 10,000 widgets they don't need, they sell them to BG cheap, and BG resells them. They send out a catalog every quarter that is actually quite enjoyable to read. I get the idea that it is a one man show. Some of the item descriptions have been great. like "I don't what this thing is, but if you hook it up to 12 volts it makes a really loud, hideous noise, and for $1.50, how could you go wrong?"

So, they may not know a lot about what they are selling, but for the price, you can do some research yourself.

[Andrew Schreiber]

Originally Posted by martin417

I have bought stuff from BG before. They are a surplus reseller. Someone has 10,000 widgets they don't need, they sell them to BG cheap, and BG resells them. They send out a catalog every quarter that is actually quite enjoyable to read. I get the idea that it is a one man show. Some of the item descriptions have been great. like "I don't what this thing is, but if you hook it up to 12 volts it makes a really loud, hideous noise, and for $1.50, how could you go wrong?"

So, they may not know a lot about what they are selling, but for the price, you can do some research yourself.

Ok, if it is a small surplus supplier that alleviates my concern somewhat, I still say be careful ordering things, too often people will try to separate you from your money.

[Rickertsen2]

I have had positive experiences with BG micro. I have also had positive experiences as a FIRST student getting free encoders from encoder manufacturers. (don't everybody swamp them at once)