i was wondering if my wiring of the minibot is okay. just to make sure i won’t be frying anything. we’ve already had some magic smoke because a wheel got stuck so we’ve already ordered more motors. here is a paint picture of my wiring. our fuse did get popped early on and we temporarily have a 20 amp fuse from the hostbot in it.
It’s fine, same way ours is hooked up.
If the limit switch stops the motors at the top, what prevents the motors from restarting as the limit switch is pulled away from the top target plate? Limit switches have NC, C and NO terminal markings. for normally closed common and normally open contacts. You need to wire between C and NC if using switch to detect top OR between C and NO if using the switch to detect the pole.
I understand how the limit switch works though we haven’t yet determined for sure where it will be placed or if we’re going to actually use two or a “regular household light switch.”
Make sure you check the current ratings on the switches you’re going to use… they need to have a 20A rating to be used safely.
Kid,
Although your wiring is workable, it will not allow the minibot to be pulled down the post. Think about an addition that will bring the minibot down at the end of the match.
We have the same wiring, and it turns off the robot at the top and lets it roll back down the pole.
There’s more than one way to mount and actuate a “limit switch”. You can do stuff with mechanisms…there’s more to life than electronics
I recommend using a switch that locks in the open position when the bot hits the top. In our testing, limit switches on the top that didn’t lock cause issues when taking the bot down. As soon as it starts to slide down, the switch is back in the initial position and will climb the pole again, then repeat. You can make an apparatus to keep the switch in the NO position when it hits, but a push button type of switch is the easiest and (should be) the most reliable.
A push-button type of switch is not on the approved list of materials for the minibot. Check <R92> - the only type of switches allowed are limit switched (I’ve never seen a push button marketed as a limit switch) and common household light switches.
When I get in today I’ll post the model number. We got them off digikey, manufactured by Cherry. They can be pulled out and locked in that position (set for NC for us), and when depressed they stay depressed as NO to disable the bot. Marketed as limit switches in digikey
That would be awesome… If it’s really marketed as a limit switch, it’ll solve this problem for a lot of teams.
Our team uses the NXT running code so we are not using switches. However, I was just curious about how it could be done with switches. Here is what I came up with and it doesn’t look like it needs any DPDT or even locking limit switches. It just needs one NO limit switch and one SPDT household switch. When the minibot deploys, it closes the NO limit switch and starts the motor climbing. After it hits the top, the SPDT switch flips and shorts the motors to ground causing it to brake. Depending on the weight of the minibot, it will either stay up there or slowly coasting down. I also came up with an alternate design where it will reverse the motor so it will climb down but with gravity helping, the minibot will practically crashing down very fast.
Yup, that’s pretty much how you can get it to work! An interesting compromise between the two looks very similar to your first drawing… except you don’t short the motor leads when you get to the top. That should allow it to fall a bit easier, without actually being powered down. Essentially, it’s the difference between brake and coast mode on the victors/jaguars.
Yup, that would work too. In our NXT controlled minibot, we programmed it to brake and it was coming down slowly at a constant speed. That’s why I thought you may need to do “brake” mode. But again, it depends on your minibot design and weight.
If you deliver the robot to the pole and it activates the pole switch, the on/off switch is redundant.
The master switch is for safety when you are handling the robot such as taking it off the pole. I assume the SPDT switch is a big house hold switch that could be easily actuated by mistake, whereas the master on/off switch from the FTC competition is harder to actuated accidentally. So before you handle the minibot or taking it off the pole, you turn the master switch off.
Ultimately what happened is that the head inspector @ the jersey regional said that the switches didn’t increase our ability to win the race, so they were legal.