Science Buddies: "Ask an Expert"

The school I work with has a robot club that competes with other area schools. For the last few semesters the middle school kids were building your line follower. This week we found that the design was gone and replaced by a Dagu kit. Those always do poorly in competitions and the kids have trouble putting them together. The assembly from the old one isn't my question really, since the kids like to explore and change the design around to improve it. My question is about the circuitry. The instructions you used to have were much easier to understand. Two kids tried these new ones and had trouble figuring out how to wire. I can write up my own but are the old ones available?

Thank your for your feedback. I am very sorry to hear that the updated BlueBot line-follower directions are not working well students in the club with which you work. This is the project you are using?

Build a Zippy Line-following Robot (BlueBot Project #3)
https://www.sciencebuddies.org/science- ... p023.shtml

The older project you used showed a red bot throughout, correct? I am able to provide you with a PDF of the older directions, and I am happy to email that to you directly if you would like, but I want to make sure we are talking about the same project.

Would you be willing to also provide some additional feedback with one of our staff scientists regarding the directions, how you feel they could be strengthened, etc? If so, I would like to put you in touch via email.

Please let me know,

Amy
Science Buddies

Amy, thanks for the reply. It wasn't that project. The robot itself was made of foam and sticks. I asked one of the kids to try wiring the circuit using the instructions on the link you offered. He said the transistors just got hot. Do you have any idea what could have happened? I had a copy of the old schematic so one of the kids is writing up wiring instructions if you don't have them.

I do have a PDF of the project directions you are needing. Because I am an administrator in the Ask an Expert forums, I do have access to your email address. Is it fine with you if I email you directly with the PDF?

One of our staff scientists has also been following this thread and would like to connect with you about the project and the circuits, so hopefully Ben will be providing some input here on this thread to help you and your team move forward successfully with the newer build.

Amy
Science Buddies

Hi englady,

I'm the author of the new project, so I'm happy to help and I'm sorry your students had a harder time using it than the old one. A few things:

1. As Amy said, we do have a PDF of the old project, so please let her know if you would like her to email that to you directly.

2. I'm very interested in your feedback about why your students found the new directions more difficult to use. Any specific feedback you have here would be very helpful and we could improve the project. For example, the new project has a slideshow that shows how to add parts to the breadboard one at a time (compared to a single image of the final breadboard in the old project). We'd hoped that would make the project easier for students who had never used a breadboard before - but it only works online, so wouldn't be helpful if you are using paper printouts. If that's the case, we could modify the project to make sure the final circuit diagram also prints, instead of the first slide which just shows a blank breadboard.

3. As for the transistors getting hot - the circuits for the old version and the new robot are nearly identical, with one very important difference. They use different transistors, which have different pin layouts. If you bought the transistors for the old project, they will not work with the circuit diagram for the new project, and vice versa. (I can provide more details and links to the data sheets that show the pin layouts if you or your students are interested).

Thanks,

Ben

Thanks for the replies and yes Amy, please do mail the PDF. I asked the student who had tried this and he said he purchased the parts in the list on the site and tried to follow the wiring diagrams. The breadboard the company sent a was slightly different shape so it didn't match the pictures. A lot of kids have problems adjusting diagrams like that. I see the same problem with lego directions. I know this student has wired breadboards in the past. He showed it to me this afternoon and looked right but it just didn't work. The parts seemed to match those in the parts list. The large group starts building them as a class next week so I thank you again for the instructions.

Hi englady,

Yes, kids will usually have trouble rearranging a circuit diagram to work with a different breadboard. That's part of why we have all the parts for the robot in a kit now, so we can guarantee that the parts will match our directions. If it helps, we do have a new breadboard tutorial:

https://www.sciencebuddies.org/science- ... d-tutorial

It explains a lot of things that might be useful to your students, like how the holes are connected inside a breadboard, and how you can build the same circuit in multiple configurations. Hope that helps, please let us know if you have more questions.

-Ben

englady-

You checked the students' work and it looked like it was wired correctly? Do you know if they were working in a carpeted room? As Ben said, the replacement circuit uses a different kind of transistor. The original used something called a Darlington and the replacement uses a MOSFET. That type can be incredibly sensitive to static electricity. If you ask the students, they'll probably tell you the MOSFETs came in protective static-proof bags to prevent damage. Unless you handle them in a workspace that's designed to be free from static electricity (referred to as ESD-safe) you run the risk of frying the parts just by touching them. I avoid using MOSFETs when possible for student projects because of that.

If your students decide to try the current design again, they can make a relatively ESD-safe environment by using a wooden or metal (and not plastic) surface, placing a piece of aluminum foil on the worktable and connecting a wire to the foil (taping it is fine). Run that wire to a copper pipe or wrap it around a radiator pipe if there's hot water or steam heat. Take a second wire connected to the foil as well and that wraps around the wrist. This connects the person's body and the table surface to earth ground and should help keep the static electricity under control.

Please write back if you have any other issues.

Howard

Thanks all of you! Amy sent me the instructions I needed. That student brought in the board after building it at home so I don't know whether he worked in a carpeted room. I'll ask. I've worked with him for 2 years on projects and he's really good with breadboarding. I'm confident that he followed the new instructions or at least tried to. I found them a little confusing myself. Last year one of the 6th graders placed in a regional line follower race with their version of this design. The foam construction lets them study how different geometries and wheel placement affect performance and that's really what I'm showing them. It's not about the circuit anyway.

Hi englady,

If you have time, I'd still be quite interested to hear what you found confusing about the new instructions. We'd hoped that the part-by-part directions, either in Table 2 of the procedure or the slideshow immediately following it, would make things easier for beginners:

https://www.sciencebuddies.org/science- ... #procedure

Could you let us know how you were viewing the directions (computer, tablet/phone, paper printout) and which part you found confusing?

Thanks,

Ben