Vex versus Boebot

Too_Many_Tools wrote:


The hubs are Vex specific. Otherwise gears are gears.

The sensors are not special in any way, and most are available for less (assuming non-Radio Shack clearance prices). The ultrasonic sensor is a Devantech SRF04, which you can get for $20-25. The shaft encoder you can make yourself for $2 or less.

Very nice, but the hubs are Vex-specific with the square shafts. If you want to use them with something else you need to figure out a different way to mount them.
-- Gordon
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Thanks for responding Gordon.
I do understand about the Vex specific square mount.
True gears are gears but good plastic gears can be tough to find.
Do you know if the gears are standard English/metric pitch?
The plastic chain is the first of its kind that I have seen...is this a commonly available item? I am use to working with its metal equivalent.
Thanks for idenifying the ultrasonic sensor...it saves me from tearing one apart. ;>)
Any idea what the shaft encoder is? pulses? LED/mag?
How about the CdS light sensor...resistance range?
In the past, I have found locating suitable wheels and gears difficult at times. What is your opinion of the Vex wheels and gears in respect to what is available today in the surplus market? Anything else comparable? I consider one can make a square hole round easier than a round hole square so modifications are no problem.
I have found myself considering the Radio Shack clearance pricing attractive enough to consider stocking up on Vex parts for other robotic projects....is anyone else doing the same?
Thanks
TMT
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Too_Many_Tools wrote:

They appear to be 24 pitch. But pitch alone isn't enough, as there is also pressure angle and the cut of the teeth. You're best off buying a set of the gears for six bucks and try them.

"Commonly available?" They come from a single source that is losing its major distributor. I don't know how common that makes them.

These are so cheap I suggest you just one of each and experiment.

If you build up from smaller bits to larger then yes. Otherwise you can drill off-center. However, drilling a round hole in the wheel, if you're planning on using the wheel as a driver, doesn't get you far. You will want to lock the wheel to the axle, so you're back to the main problem of all wheels: how to get the wheel to interface to your motor or drive shaft.
The RadioShack.com site lists a lot of the components as out of stock, and many stores are returning the inventory to Radio Shack to clear it. You should get this stuff now at your local store if you want to enjoy the sale prices. They do have a lot of the full kits, but I don't think the same applies to the accessories.
-- Gordon
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Thanks for the comments on the gears and chain....I did not know that it was a single sourced part...not good....I was hoping that I had just not been aware of it.
I have access to most of the sensors except for the light sensor....guess we will buy one off Ebay and reverse engineer it.
I am aware of the stock situation on the Radio Shack site and the fact that supplies are selling out or being sent back to corporate. I do understand that arrangements have been made to support Vex after Radio Shack completes its exit from this market.
TMT
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It's just a disk with slots which generates pulses as it turns. I don't know what the sensor actually is - LED with something I guess. It connects as a digital input and just alternates between 1 and 0 as the shaft rotates. I think one document I read said 100 slots per revolution, another I think said 90. It doesn't encode the position of the shaft, or the direction of the turn. It can be used to track revolutions but since it doesn't use two sensors to allow you to track the direction of turn it only works well for tracking speed and total distance and not for trying to track shaft position.
--
Curt Welch http://CurtWelch.Com /
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