Re: Minibot climb rate
 

Be careful, you can not use one four-way switch to reverse your motors. You need to use two Three-Way Switches or one Double pole-Double throw Switch. I did electrical work for 9.5 years.
Mentor Mac mccubbin99@live.com
240-405-9213 301-831-0407
Mt.Airy,Md. Team 686

Re: Minibot climb rate
 

Apparently the GDC thinks otherwise

From Team Update #7:

Re: Minibot climb rate
 

This circuit should be correct for using a 4 way switch to reverse the motors.

Dean

Re: Minibot climb rate
 

Yes a 4 way switch will reverse your motors, the key is to put the battery connections on one color screws (we used the black) and the motor on the other color screws. Doesn't matter which is which just that both leads of a respective item are connected to the same color screws. If you want to change which direction of the sw is up and which is down reverse the motor leads. It is also possible to wire it so that one of the motors works in brake mode while the other has power in the "down" mode.

Re: Minibot climb rate
 

Here's a couple updates. This is a picture of the bot in it's functional state. We'll be tweaking on it a bit, but it works as planned.



Our goal was a sub 5 second robot. Currently, and without much fine tuning yet, we are at 4.5 second from the platform to the top of the pole without the sensoe plate.

http://www.youtube.com/watch?v=HnKO-nry2EA

Re: Minibot climb rate
 

We hit 2.71 seconds today (including the battery and all necessary switches), and that's without our new custom wheels (which aren't back from the CnC mill group yet). We were very excited, as prior to this we had been stuck at around 4.5 seconds!

Re: Minibot climb rate
 

what did you use to have the minibot turn on when it hits the pole. we're using magnets also.

Re: Minibot climb rate
 

There is a polycarbonate rod the extends past the magnet. When the magnet pulls the bot to the pole, it pushed the rod back, which in turn closes the main electrical switch.

Re: Minibot climb rate
 

um... where's your battery? we tried magnets in the early stages of our design and they would work just fine untill we put the battery on and the whole thing would fall right off.

Re: Minibot climb rate
 

I think this was discussed as not allowed on several other threads. Plus team updates it was also clarified. Maybe someone could help post those rules. ( psst I am at work)

Re: Minibot climb rate
 

If you look at the date on the original post (10th of jan) you should notice that team update one which disallowed the use of surgical tubing for upward movement was released the day after I posted that.

and yes, surgical rubber is not a legal source of energy to climb the pole per the current rules as G19 states.

Re: Minibot climb rate
 

Watch the video. The battery is opposite the motors.

Re: Minibot climb rate
 

I have taken a different approach to estimating the theoretical minimum time possible for the mini-bot to reach the top of the 10 ft pole.

Rather than the using the power output from the motor, I used the rated no-load speed of the Tetrix motors (152 to 154 rpm) to estimate the shortest time possible. This rpm for the motor would produce a Motor Rotation Time for one revolution of 0.39 seconds in an idea world with no load (battery, motors, framework, etc.).

This means that a 3 inch wheel directly attached to the motor would require 4.96 seconds to reach the top of the 10 foot pole. Similarly, a 4 inch wheel would reduce this time to 3.72 seconds. Using a 1:3 gear train would reduce these times to 1.65 and 1.24 seconds respecively, but reduce the effective power of the motors to lift.

Motor rotation time = (60 sec/ 1 minute)* (1 Minute / 154 revolutions)
= 0.39sec/rev

Revolutions to top = (Pole Hieght) / (diameter of Wheel * Pi)
= (120 inches) / (4 inches * 3.1415)
= 9.55 revolutions of the 4" wheel

Time to top = (Revolutions to Top) * (Motor Rotation Time)
= (9.55 rev) * (0.39 sec/rev)
= 3.72 sec for a 4" wheel to reach the top of the poe.

Re: Minibot climb rate
 

Clocked in at 1.7 Seconds tonight! :D

Re: Minibot climb rate
 

our minibot goes up the pole in just under 6 seconds if the wheels don't slip, actual test of real minibot and real pole.

we can deploy and climb the pole in under 10 seconds under software control; it works about half the time. the other half the alignment isn't quite right and it doesn't work.

jw