Will this circuit work?

[Al Skierkiewicz]

JJ,
The simple answer is no. Zener diodes have some specific requirements for implementation. Motor operation is one of the biggest areas of confusion on the robot. While voltage is discussed in terms of motor speed, it is the current that is actually making things happen. A a voltage regulator, the zener diodes would need to dissipate huge amounts of power when the motor is not running. As a hint for your team to consider, the minibot does not meed to stay at the top of the post. It merely must hit the target with enough force to trigger the goal, once is enough. Then it can return to earth. I like that your rookies are thinking. Keep asking, this is one of the more interesting questions so far.

[Brandon_L]

Just from reading this, I have a question..

You HAVE to use some sort of motor controller on the minibot?

[Al Skierkiewicz]

Originally Posted by Brandon_L

Just from reading this, I have a question..

You HAVE to use some sort of motor controller on the minibot?

Nope,
If you use the NXT brick then you must use the motor controller since the brick does not control Tetrix motors directly.

[liam.larkin]

Staplemonx

Lets throw out your first circuit things like diodes and logic circuits are not allowed on the minibot per rule R92

My first question is why are you trying to even have a 5% mode. I gather you think it is required to keep the minibot at the top after you make contact with the scoring disc. This is not a requirement.
Or does this 5% mode keep the robot on the pole like you are using one of the motors to grasp around the pole?? However if I am inferring correctly I dont think this is the case. So I really believe you can throw this 5% mode out the "design window".

In this case here is my reccomendation. Limit switch in series with the battery and circuit. It is in its normally open position. When the minibot makes contact with the pole it closes the switch initiating your entire circuit.

Additionally you have a normal light switch somewhere at the top of the minibot with a little plate or finger of some sort pointing up. This switch is in its normal on/closed position and is in series with your motors.

As your robot climbs the pole this finger makes contact with plate setting of the scoring system and simutaneously moving the switch to the off position. This cuts the power to your motors. If you are worrying about the minibot not coming back down and not being able to get at it. I would recommend hooking the switches' off position in such a manner as to shunt the motors. This should get them to back drive when power is cut and the robot will "coast" back to the ground.

NO NXT or speed controllers.

[tagayoff]

Originally Posted by liam.larkin

Staplemonx

Lets throw out your first circuit things like diodes and logic circuits are not allowed on the minibot per rule R92

My first question is why are you trying to even have a 5% mode. I gather you think it is required to keep the minibot at the top after you make contact with the scoring disc. This is not a requirement.
Or does this 5% mode keep the robot on the pole like you are using one of the motors to grasp around the pole?? However if I am inferring correctly I dont think this is the case. So I really believe you can throw this 5% mode out the "design window".

In this case here is my reccomendation. Limit switch in series with the battery and circuit. It is in its normally open position. When the minibot makes contact with the pole it closes the switch initiating your entire circuit.

Additionally you have a normal light switch somewhere at the top of the minibot with a little plate or finger of some sort pointing up. This switch is in its normal on/closed position and is in series with your motors.

As your robot climbs the pole this finger makes contact with plate setting of the scoring system and simutaneously moving the switch to the off position. This cuts the power to your motors. If you are worrying about the minibot not coming back down and not being able to get at it. I would recommend hooking the switches' off position in such a manner as to shunt the motors. This should get them to back drive when power is cut and the robot will "coast" back to the ground.

NO NXT or speed controllers.

My question is where do you find a limit switch that carries 14 amps of current?
Thanks

[The Lucas]

Does any one know if 3-way light switches are legal for Minibot use? They seem common (ubiquitous) to me. Could be a good Q&A.

If 3-way switches are legal and you still want the minibot to hold at the top of the pole, there is a way (think about speed controller "Brake Mode").

[Al Skierkiewicz]

Brian,
Light switches were defined by the Q&A
"For the purposes of the 2011 competition, a common household light switch is any electrical switch that would normally be mounted in a wall outlet box with household wiring, typically available at a home supply center (e.g. Lowes or Home Depot).

Minor modifications of the switch (e.g. removing the mounting tabs) are permitted, as long as the basic structural integrity and overall safety of the switch are not compromised. "

Three way and four way switches would fit this description.

[liam.larkin]

tagayoff.

Grainger-they sell all types and flavors that can handle much more then your required 14 amp. Where is that number coming from btw? Our motors are not approaching anywhere near that much current.

[tagayoff]

I saw in one post the stall current of one motor was 7 amps. Since both on start would be stalled . The switch would have to handle that much if it was to survive long I think. Of course how many times does it have to climb the pole. Then again if you make it to the finals that could be a bummer if it failed that last time.

[staplemonx]

Thanks agian for the knowledge folks

Here is our updated plan. Lets see if we understood the feedback correctly.

[Mike Betts]

Originally Posted by staplemonx

Thanks agian for the knowledge folks

Here is our updated plan. Lets see if we understood the feedback correctly.

If the devices you are using are in compliance with <R92>, you should be all set. That being said, I'm not sure that they are...

[liam.larkin]

That looks good to me.

Switch one is normally open

Switch two is normally closed

I think that will work well. Motors in Parallel??? I mean sure why not harder to physically wire but sure...for this application series will be work just fine

[Vikesrock]

Originally Posted by liam.larkin

I think that will work well. Motors in Parallel??? I mean sure why not harder to physically wire but sure...for this application series will be work just fine

That's not correct at all. Motors in series would get approximately half the voltage and spin half as fast. In a Minibot race you really don't want to do that (for the way up at least).

[liam.larkin]

Yes the voltage drop across them would be cut in half.....Yes right DUH.....Sometimes I loss my head

[PAR_WIG1350]

Originally Posted by Mike Betts

If the devices you are using are in compliance with <R92>, you should be all set. That being said, I'm not sure that they are...

If the "shunt fields" are just coils that they manufacture out of the allowed wire, then they should be fine, if they are anything more than that, they might have trouble. That being said, the "shunt fields" aren't really necessary, the minibot should do just fine if it is simply turned off. if this makes it fall too slow, I suggest a loop of lexan for a bumper.