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-   -   Homemade resitor (http://www.chiefdelphi.com/forums/showthread.php?t=94110)

AlDee 30-03-2011 00:41
Re: Homemade resitor
 
Quote:
Originally Posted by EricH (Post 1046587)
I could argue that point.

I have a 6" connection. I connect the two points with 10' of wire. Is it still being connected? Absolutely. Is there a lot more resistance than if I only used 6" of wire? Yep.

<R92> does not say that you can't make some other part out of the stuff in it. For example, I could use the rubber bands and surgical tubing to make a nice powerful torsion spring to store energy for latching on to the pole. Is it legal, despite springs not being on the list? Yep. (Now, if I powered vertical motion with it, then I'm illegal under a different rule.)

So, if I can take the 18-gauge wire, connect one end to one connection, connect the other end to the other connection, and bundle the rest safely in the middle (using legal material for the bundling), I just made a resistor out of 100% legal material. The resistor should be legal.

However, again, I am not a source of official answers. The Q&A is, and the inspectors at your event are. If you would like to say what the resistor is used for, then there may be other ways to do that that are clearer with respect to the rules.
I would agree. Any wire, 6 inches or 10' has some resistance. So, I cannot see how a 10' piece could be disqualified. But your point is taken on being up to the the event inspectors. In 2009, our front bumpers failed inspection at the championship, because the plywood backing inside was a half inch shorter than the minimum, even though the bumpers themselves were technically the correct length, and they had previously passed inspection at the regional. In the end it came down the the inspector's interpretation of the rules, even though there was no rule that specifically said the internal backing material had to be a specific length.

Mr V 30-03-2011 00:44
Re: Homemade resitor
 
Quote:
Originally Posted by NOV8R (Post 1047222)
Al, we never reversed the voltage to the motors. We simply added additional resistance in the circuit to reduce power. The reduced power wasn't enough for the minibot to maintain position on the pole and it would decend. Yes, shorting the motor leads (what we are now doing) is working well also.
Well that explains why you were heating the motors up, I'm surprised you didn't burn them up back driving a powered motor.

AlDee 30-03-2011 00:46
Re: Homemade resitor
 
Quote:
Originally Posted by EricH (Post 1046587)
I could argue that point.

I have a 6" connection. I connect the two points with 10' of wire. Is it still being connected? Absolutely. Is there a lot more resistance than if I only used 6" of wire? Yep.

<R92> does not say that you can't make some other part out of the stuff in it. For example, I could use the rubber bands and surgical tubing to make a nice powerful torsion spring to store energy for latching on to the pole. Is it legal, despite springs not being on the list? Yep. (Now, if I powered vertical motion with it, then I'm illegal under a different rule.)

So, if I can take the 18-gauge wire, connect one end to one connection, connect the other end to the other connection, and bundle the rest safely in the middle (using legal material for the bundling), I just made a resistor out of 100% legal material. The resistor should be legal.

However, again, I am not a source of official answers. The Q&A is, and the inspectors at your event are. If you would like to say what the resistor is used for, then there may be other ways to do that that are clearer with respect to the rules.
I would agree. Any wire, 6 inches or 10' has some resistance. So, I cannot see how a 10' piece could be disqualified. But your point is taken on being up to the the event inspectors. In 2009, our front bumpers failed inspection at the championship, because the plywood backing inside was a half inch shorter than the minimum, even though the bumpers themselves were technically the correct length, and they had previously passed inspection at the regional. In the end it came down the the inspector's interpretation of the rules, even though there was no rule that specifically said the internal backing material had to be a specific length.

AlDee 30-03-2011 00:53
Re: Homemade resitor
 
Quote:
Originally Posted by Mr V (Post 1046764)
If your minibot doesn't back drive after it's collision with the trigger then a 4 way switch can be used to put one motor in "brake" mode while having the other drive reverse.
What type of 4 way switch are you using? Is it a light switch? I took the term "Standard Light Switch" to mean a single pole single throw switch. Does a 2-way or 3-way switch qualify as a standard light switch?

The Lucas 30-03-2011 01:06
Re: Homemade resitor
 
Quote:
Originally Posted by AlDee (Post 1047255)
In 2009, our front bumpers failed inspection at the championship, because the plywood backing inside was a half inch shorter than the minimum, even though the bumpers themselves were technically the correct length, and they had previously passed inspection at the regional. In the end it came down the the inspector's interpretation of the rules, even though there was no rule that specifically said the internal backing material had to be a specific length.
In that anecdote, it didn't come down to some inspector's arbitrary interpretation. That was the rule as originally written, immediately clarified by the GDC in the Q&A (below), and reemphasized in Team Update #2
Quote:
Minimum Length Bumper Segments
Minimum Length Bumper Segments
Posted by FRC1114 at 01/07/2009 05:58:04 pm
<R08>-A states "BUMPERS must be build in segments, with a minimum length of six inches..."
<R08>-J states "Corners and joints between BUMPER segments may be filled with short vertically oriented pool noodle..." Will bumpers be measured by the length of the plywood backing, or the plywood backing + any vertically oriented pool noodles used for corners? i.e. Can we have a minimum length 6" bumper, with less than 6" of plywood.
Cheers,
Re: Minimum Length Bumper Segments
Posted by GDC at 01/09/2009 10:11:08 pm
Please refer to Team Update #2. As indicated in Rule <R08>, BUMPERS must include a solid plywood backing (as well as the pool noodles, clamping angles, and fabric cover). The length of the the bumper assembly that includes all of these items is what determines the "bumper length."

Mr V 30-03-2011 02:28
Re: Homemade resitor
 
Quote:
Originally Posted by AlDee (Post 1047265)
What type of 4 way switch are you using? Is it a light switch? I took the term "Standard Light Switch" to mean a single pole single throw switch. Does a 2-way or 3-way switch qualify as a standard light switch?
Well our robot does back drive so we aren't using a 4 way. Unfortunately the rules changed a couple of times so there is lots of confusion over this issue. So they do allow pretty much any sw designed for wall box mounting to 2-way, the most common sw, as well as 3 and 4-way switches are legal.
To cloud things even more household wiring sw terminology is different from other types of wiring terminology. Basicallly in household switches the # before the -way refers to the number of terminals.


To wire it to provide "reverse" to one motor and brake to the other:

A 4-way switch has 2 black color and 2 brass color terminals, so we'll call them bl1, bl2, br1, and br2. Connect B+ to bl1 and B- to bl2. Connect forward + for motor a and b to br1 connect motor forward - for motor a to br 2 and motor forward - to bl2.

In sw position 1 terminal bl1 is connected to br1 and bl2 is connected to br2. Flip the sw to position 2 and bl1 connects to br2 and bl2 connects to br1. So in 1 position both motors are powered forward and in the other position motor a is powered reversed and both motor b leads are connected together which just so happens to be also connected to battery - which plays no part in that circuit. both of the brake motor leads could just as well be connected to battery +, and it would still work the same.

However to have a minibot that doesn't back drive it needs to have a high effective gear reduction and be very light.

Al Skierkiewicz 30-03-2011 08:50
Re: Homemade resitor
 
Chuck,
Now I see. Interesting idea. I haven't heard of anyone doing that so I was having a hard time understanding your description.

Teched3 30-03-2011 09:05
Re: Homemade resitor
 
What does your minibot weigh? :) :)

Quote:
Originally Posted by Mr V (Post 1047291)
Well our robot does back drive so we aren't using a 4 way. Unfortunately the rules changed a couple of times so there is lots of confusion over this issue. So they do allow pretty much any sw designed for wall box mounting to 2-way, the most common sw, as well as 3 and 4-way switches are legal.
To cloud things even more household wiring sw terminology is different from other types of wiring terminology. Basicallly in household switches the # before the -way refers to the number of terminals.


To wire it to provide "reverse" to one motor and brake to the other:

A 4-way switch has 2 black color and 2 brass color terminals, so we'll call them bl1, bl2, br1, and br2. Connect B+ to bl1 and B- to bl2. Connect forward + for motor a and b to br1 connect motor forward - for motor a to br 2 and motor forward - to bl2.

In sw position 1 terminal bl1 is connected to br1 and bl2 is connected to br2. Flip the sw to position 2 and bl1 connects to br2 and bl2 connects to br1. So in 1 position both motors are powered forward and in the other position motor a is powered reversed and both motor b leads are connected together which just so happens to be also connected to battery - which plays no part in that circuit. both of the brake motor leads could just as well be connected to battery +, and it would still work the same.

However to have a minibot that doesn't back drive it needs to have a high effective gear reduction and be very light.

Mr V 30-03-2011 12:37
Re: Homemade resitor
 
Quote:
Originally Posted by Teched3 (Post 1047326)
What does your minibot weigh? :) :)
~3.1 lbs


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