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Resolved Resolved by Dunning-Kruger!

Sabertooth/Kangaroo With Different Motor/Encoder Combination

Since I know some of you have used the Sabertooth and Kangaroo I figured I would ask opinions.

I have decided on the Parralax Arlo base for my next robot chassis. I will use the caster's from parralax.

I will most likely be using the Sabertooth and kangaroo combination for motor controller/PID but I am not decided on this and open to suggestions.

I also find myself in a heated mental debate between the wheel/motor combination from parralax or the Zagros Rex motors and wheels combined with the Sabertooth/Kangaroo.

Item 1:

One of the key items for me is how well the encoders between the two different motor/wheel sets works with the Sabertooth and kangaroo.

Item 2:

The other item floating in my mind is the ground clearance between the two motor/wheel sets. It seems at least to me that the Zagros wheels would provide more ground clearing but since the base plate of the chassis provides stability to the base platform I am not really sure if using the Zagros motors are feasible.

Item 3:

Since I am going to build a body, arms and head on top of the base the torque and weight carrying ability is important.

Item 4:

I need to be able to control both the position and speed of the motors at the same time. For example example I should be able to have to robot move lets say 1 feet at a certain speed.

I know this is kind of an open ended questions but if anyone have used any of these wheel/motor combinations please provide your 2 cents as it relates to the items listed above.

I appreciate any comments or insights you guys can provide.


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#166  
It looks like there is a shaft on the back of the motor but unless I had one, I don't know what it would take to add an encoder to the back of the motor. The other option is to add it at the wheel end of the motor. Without specs on the motor, I wouldn't be able to tell you if you would probably need a logic divider or not.

Here is what I mean...

If you had a motor that was geared 200:1 and you had an encoder on the back shaft of the motor that was a 500 count encoder, you would get 100,000 counts or ticks per revolution of the wheel.

If the encoder were a 100 count encoder and it were on the wheel end of the motor, you would get 100 counts or ticks per revolution.

The gear box and the placement of the encoder in relation to the gearbox has a lot to do with the level of detail by the number of ticks per revolution.

The issue comes in if the gearbox is say 127:1 and your encoder is before the gearbox, causing the encoder to spin 127 times per revolution of the wheel. This also gives you very accurate movement though.
#167  
Here is a photo of a sample of one of the boards. There is a modification to them to allow index to also be used, and will have thicker leads and less space on the sides, but this will give you an idea of what you would get to solve the high encoder count issue for these motors and these kangaroo.

I will start taking orders for these. Just send me an email. My email address in on my profile. They will be $8.00 each. If I already have an email from you then I already have you down for the number that you ordered. It will be about 2 weeks before I can have these made and shipped out.

This is a first come, first served deal. There will only be 20 available in the first order, of which 10 are still available.

Payment will be available through Paypal and the details will be handled through email for any orders.

User-inserted image
#168  
i was able to squeeze 2 more of these logic dividers onto my board design. Because of this there will be 8 more of these available and it reduced the cost to $8.00 per board.

The order for the boards will go in tomorrow. It will take about a week for me to receive these boards, and then about a week to make and test them before shipping.

I will update this thread with the current status as I know more.

Shipping inside the US will be done through USPS. Outside of US, I will have to see who has the best rate available. I know some have different shipping methods that they prefer. We can discuss the rates and all through email when the orders are ready to ship.

Payment will be due when these are complete and I have tested them and know that each one is working correctly.

I will provide post headers but wont solder them so that you have the option of using something else in this location. If you want me to go ahead and solder the post headers onto the board, just let me know.

Thanks
David
#169  
The board order has been placed. I should have them by this time next week. All other components for these flip flop circuits are waiting to be soldered onto the boards.

There are 10 of these logic divide by 2 circuits available still. The cost that is being charged will cover the cost of having the boards made. The cost of the other parts of this process except shipping are being absorbed due to the fact that this order is also helping me with the cost of having the (hopefully) final Rafiki prototype boards made. If it is found that these are wanted by more people after this initial order is fulfilled, I will make a run of just these boards.

Anyway, two weeks from today, I hope to have the orders fulfilled and shipped out.

Thanks
David
#170  
These boards are in a Shipping status from the board manufacturer. I expect to receive them by the end of this week still and will start fulfilling orders. I have 10 available for purchase at $8.00 each. If this board tests out correctly, I have another order set to go in which will allow 16 more of these to become available. I think I will wait until these sell or are used by me before ordering another set of boards with these flip flop circuits on it. The other future board designs will have more of the USB Breakout boards if anyone is interested in buying any of those. I think I will sell these for about $4.00 each.
#171  
The boards should ship to me today. I gave them the wrong city name in the address to ship them to. Stupid mistake, but this will probably delay me building these until next week. I should be able to knock out the ones that people have ordered pretty quickly. Sorry about that to anyone who is in a rush.
#172  
It looks like I will receive these boards on Monday. I have to go to Dallas Monday afternoon and won't be back until Wednesday night. This cuts into the time that I was going to use to make these. I may just bring them with me to Dallas and use the DPRG facilities to make these. IDK if it is a good thing to show up to my first meeting and do this or not, but may try. If I can get them cut out of the board before I leave, I will bring them. If they come to late in the day, I will have to wait until Thursday night to start on these. Anyway, just giving a status update to those who wanted these.
#173  
There is no reason to hurry for me Dave.
These are going into my next project, so whenever.

Thanks for doing this for us.
#174  
@David, no worries David go to your meeting come back and finish your chips I'm in no rush I still have to order my motors with encoder anyway . This way you can focus on your meeting and not have to be in a rush to finish the chips thanks for all your work

Sorry for no punctuation's I am talking to cell phone
#175  
I didn't get a chance to cut these boards down while in Dallas. I will cut these down this weekend and build them out. My hope is to mail them out early next week.
#176  
I had to make another board order for Rafiki, so it looks like there are going to be 22 of the divide by 2 circuits available for purchase by the end of next week. This isnt something that will affect the ones ordered but was an issue on another part of the board. I am still shooting for this weekend to have the first batch completed.
#177  
Just finished making these. I will test them out tomorrow to make sure they all work. I'll send those that sent me an email an invoice through paypal this weekend.
#178  
Just finished testing every one of these individually. With 12.8 V to the motor I get right around 24K ticks per second. This should put these at about 32K per revolution which is correct. I will send invoices later today and will be shipping these on Tuesday. American holiday prevents me from mailing these out on Monday. I am including your basic pins with these and these pins will not be soldered to the board.

Thanks for your patience. BTW, there are 22 available for sale if anyone needs these in the future.
#179  
Invoices have been sent on domestic orders. I will need to go to the UPS store for international orders which I will do tomorrow. I will be sending all of these out tomorrow.

Total cost for domestic with 2 day shipping is $22.80 for 2 of them. I have 4 more built, tested and ready to ship if anyone would like them. The others after this will be built and tested as ordered, but all of the components are here so it wont take much time at all to fulfill an order.

Thanks
David
#180  
Money sent.

Thanks for doing this for us David.
#181  
The funny thing is that a week ago at the Dallas Personal Robotics Group meeting, there was a group of people discussing this same issue but with an Arduino controller and a different motor. They were looking for a way to reliably reduce the counts per rev on a motor due to the encoder being behind the gearing in the motor. I told them some programming solutions like just catching the rise and discarding the drop on each of the encoders and such. They didn't like this solution so I then said that you could use a flip flop type solution. They said that they didn't want to add other IC's to the robot that someone would have to design and build.

They are trying to come up with a basic robot platform that would be expandable and allow a novice to learn about robotics and compete in a competition that they have coming up. This is when I mentioned EZ-Robot to them and described the EZ-B and ARC to them. I don't think that they believed me about ARC and how easy it would be to build what they were designing. Anyway... next time I am down there, I will demonstrate it to them and also bring some built flip flop circuits down to them to use/buy. It always amazes me when I talk to expert robot builders about how simple things can be and they seem to discount it because it is easy. I thought that was the entire point of what they wanted to do, but I was new among them so there is no level of trust built yet for them to believe what I am saying, and I get that.
#182  
Cochran Robotics online store is now, well, Online...
Anyone needing these in the future can order from CochranRobotics.com.
I am now finished posting on this thread:)

Thanks
David
#183  
Zagros is having issues keeping the motors in stock now. This is an issue for me...

I am in discussions with GLOBE to be a distributor for these motors now. I should have a quote in a couple of days for a purchase that will allow you to get these motors/encoders from me. I have asked for 2 different products to be quoted. One will use the Avago 500 count encoder and the other will use the Avago 256 count encoder. The 256 count encoder on these motors is not an existing part number at GLOBE meaning that they would probably cost me more, but we will see. The 500 count encoder on these motors is an existing part number and is what is sold by Zagros when in stock. It is also the one that requires the use of the logic divide by 2 boards for sale on my website to allow it to work with a DE Kangaroo controller. I should have news in the next couple of days and will update here if I will be able to carry these motors or not.
#184  
I can sell these motors for about $200 each. This leaves me only about $20 profit. These would have 256 count encoders and would eliminate the need for the divide by 2 circuit. If you would be interested in doing this, please email me. My email is on my profile. This gives 32,512 ticks per rotation. With a 4 inch wheel, this gives you about .01 mm accuracy.

Thanks
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