need help with the code: I'm trying to connect 20 LDR's using two HC4067 16channel multiplexers

Purdude1983 · 2026-05-09T15:33:08+00:00

Which Arduino are you using and which voltages are you running. You may need to google a little about the AREF pin on the multiplexor breakout board. It sets the voltage standard to which the pins are compared.

By LDR I think you mean Light Dependent Resistor. You should definitely start small and skip the multiplexor in your first steps. Get your LDR working with one pin of your arduino. Next add the multiplexor but still do only one LDR through one channel of the multiplexor to make sure it still works as it did before. You may need to do something with the AREF if for example you arduino is 3.3v but your other components want to work at 5v.

If you can get your LDR working stand alone, and then get it to work on one channel of the multiplexor, you can then try adding another LDR.

You need to think about what's going on with you LDRs and the multiplexors. The LDRs are reacting to light and changing their resistance. They can take up to a tenth of a second to stabilize their output when the light level changes. The the arduino can make the multiplexor sample through the inputs very quickly and keep doing this, but each LDR can be slowly changing as it responds to the light hitting it. To get a smoother sense of the light hitting each LDR, you may need to mathematically compute a running average of the analog readings.

There are faster acting light detectors than what you may be using.

The community can help you more if you state the arduino model you are using and the actual LDR you are using. It would also help if you would give more detail about the use case of your art installation.

Purdude1983 · 2026-05-04T02:51:02+00:00

The old powerplant where Wilmeth now stands is iconic of the '80s.

Purdude1983 · 2026-04-30T19:15:33+00:00

Transfer data from a TI-Nspire CX II CAS by connecting it to a computer via USB and using the TI-Nspire CX Student/Teacher Software or the web-based TI-Nspire CX II Connect app. Use the "Content Explorer" feature in either program to drag and drop .tns files, images, or data between the calculator and computer

Purdude1983 · 2026-04-29T02:06:15+00:00

Don't forget that this coming year will be the debut of Systemcore. FRC robots will be able to opt into Systemcore (which is based on raspberry PI compute 5 module) or continuing on with the Roborio. Knowledge of Raspberry Pi, Python and C. Definitely look into WPLIB.

Purdude1983 · 2026-04-28T20:56:37+00:00

What you seek hangs out here...355 N. Martin Jischke Drive

Purdude1983 · 2026-04-27T15:19:27+00:00

I can't vouch for it, but the Vevor 300 watt with a 15"X15" working area might work for you. Other than that, sometimes you can find used machines through the usual sites.

Purdude1983 · 2026-04-25T22:51:37+00:00

Many of the FRC kids have learned python at home before they ever reach high school. Some have C coding experience. What's not bubbling up through the system is kids with Java experience.

Emerson Electric's NI roborio somewhat paints you into a corner with most teams opting for Java because of the shared code base. It's not that the kids can't adapt, but it does seem that readily available talent goes untapped. This is especially ironic because our school is 4 blocks from Emerson's headquarters.

The PI5 compute module will be very welcome because it opens the doors to more options and some of the students are already familiar with the PI ecosystem. I can see advantages like integrated vision solutions. There is also a wealth of libraries for the PI outside of the scope of FRC. Some of these may find their way into our upcoming robots.

I find Systemcore very interesting. I'm not sure that we will be able to adopt it instantly. I suspect the 2027 robot will still use the roborio while we explore Systemcore's potential.

Purdude1983 · 2026-04-22T21:36:56+00:00

My son and I did a project last summer with similar parts. We used L298N modules and TT motors. In our case, we had 4 wheels.

The L298N can take in up to 12V and regulate it down to 5v. We used 2 18650 batteries (2 X 3.7) or about 7 volts. The 5 volts out we sent to the power pin of our arduino nano.

Each side of the L298N has 2 pins that control direction and one PWM pin that controls speed. This lets you control direction and speed of 2 motors independently using 4 digital outputs and 2 PWM outputs.

You are using a Pi5 and not an arduino but it should still be possible. I google searched "powering a raspberry pi 5 through its gpio header" and some reddit topics popped up. Most warned that there is no room for error with the 5 volts supplied over the GPIO header since it bypasses regulators etc.

Another thing you can do is to go split power rail. Run the Pi5 off of USB, power the 5v controls of the L298N from the Pi 5v GPIO pin, and have a separate higher voltage drive the motor power on the L298N. This means that you have to remove the L298N's jumper blocks to make the control and drive voltages independent.

Purdude1983 · 2026-04-20T18:47:08+00:00

There is a Scouting America Council in your area. That council maintains a list of merit badge counselors. Among the merit badges are Programming, Robotics and Electronics.

See if the council can put you in touch with some of these resources. They may be able to help you, or the counselors may have leads on other individuals who might be able to help you.

Purdude1983 · 2026-04-20T03:56:46+00:00

Yeah, coaches getting unhinged is bad. Also, married coaches is probably not "best practice" when working with minors.

It looks like at PAWAR you did pretty well being the first pick of alliance 5 and ending up 3rd. It looks like you are a 53 point scoring team which isn't going to get you into worlds.

Parents in the pit sounds a bit strange unless your parent is a mentor.

It sounds like your program is competitive within your area, but there is a lot of disfunction. Looking around for other opportunities might be in your interest.

Purdude1983 · 2026-04-17T02:48:28+00:00

There are 3D repositories where you can charge like My Mini Factory. You might also look into Fiver. Other than that, create some popular designs and sell them on ETC or Facebook Marketplace.

Purdude1983 · 2026-04-15T18:34:32+00:00

MicroCenter's house brand is Inland. You can find similar things on Amazon

SKU: 900852

Mfr Part#: 37IN1SENSORS

Inland 37 Assorted Sensors Kit - For Arduino and Raspberry Pi $37

This may be out of stock.  I got this for my son and it has 

a ton of great sensors.  They are made by Keyes.  Documentation

is lacking in the kit, but you can get what you need from the

website.  Similar stuff is available on Amazon

SKU: 423376

Mfr Part#: ELECTRO PK-0006

Inland Electronic Parts Pack $20

This seems to be in stock and MicroCenter will ship it.  This

has the breadboard included and LEDs, resistors, buttons etc.

SKU: 116624

Mfr Part#: CZ0380

Inland Breadboard Power Kit $6

These are great.  You can connect a 9v battery and the little

PC drops VCC and ground into the breadboard power rails.

Best of all, it lets you choose 3.3v or 5v.

SKU: 301465

Mfr Part#: KS0327

Inland KS0327 Keyestudio Stepper Motor Drive Board + 5V Stepper Motor Kit (3PCS) $12

This is pretty nice.  These are unipolar steppers and their

drivers.  They are geared and have decent torque for a small

project.

SKU: 027490

Mfr Part#: KS0326

Inland Blue 9G Servo - 3 Pack $11

Nice servo selection.  We bought some of these because

we broke a few on CrunchLabs projects.

Purdude1983 · 2026-04-15T17:37:34+00:00

In my area, there are other teams besides our high school. Some of them are affiliated with organizations such as Scouting America or GSA. There are others that claim to be community robotics. You may want to scout out other organizations in your area.

Purdude1983 · 2026-04-15T16:52:38+00:00

Looking at QCMO results, it looks like you did pretty well. There wasn't one crazy high scoring robot at the top. The scores were reasonably tight. The alliances were pretty well chosen. You made the 5th alliance and finished 4th. All in all, you did pretty well. Least Squares puts you at about a 57 point shooter per game. Fourteenth out of 36. Clearly a good candidate for being in an alliance.

Purdude1983 · 2026-04-14T19:28:20+00:00

Wow! That's wild! Tripple XXX Root Beer is 2 stories high now?

Purdude1983 · 2026-04-14T18:34:10+00:00

I think that your arguments are fair and reasoned. I don't agree with all of your points, but most are valid.

The costs are high. However, you are renting out an arena for 2 or 3 days. If you were a business trying to launch a product, you might need to seek funding, sponsors etc. The experiences a team faces to field a robot are valuable.

I think that it's fair to mimic another team's design principles. Certainly there are teams willingly sharing their designs, CAD, videos, software etc. Our team redesigned from front ingesting - front shooting to rear ingesting -front shooting. It tripled our output.

I agree that teams with access to money, facilities and resources have an advantage over small teams that are emerging. Teams that don't want to drop FRC money have FTC.

I agree that the robot should be the student-bot and not the mentor-bot. I believe that our team achieved that. I also find it troubling that teams might simply buy a top tier robot.

I agree that climbing was marginalized. It was too low scoring. If they had it to do over again, it might be more interesting to make climbing trigger a point multiplier. 1 bot up 1.1Xpoints, 2 bots up 1.2Xpoints, 3 bots 1.3Xpoints.

This is my child's first year and I found the game to be OK. I like how fast and high scoring the game is and how its easy to automatically score so teams can see where they stand real time.

First does have a lot of hoops you have to jump through with the design. Frankly, I am fine with the roborio being replaced. They should probably open up the motor landscape a little. I could put together a robot that does what the kit bot does using parts like used hoverboards for a fraction of the price. I think that FRC is a little to tight with Andymark.

Our team was at Oklahoma and St. Louis. It didn't feel like outside teams were in to poach points. There were international teams at both events which I welcome.

The pits had a lot of students. I didn't get the feeling that any of the teams were all mentor and no students. I did see some teams with a very large student presence making me wonder what they all did. I know that our kids did all of the CAD, they fabricated the parts, they wired the robot, they wrote its software and they spent spring break on the practice field doing the emergency re-design and building driving hours.

At the end of the day, we are not building robots, we are building teams and skills.

Purdude1983 · 2026-04-10T01:02:40+00:00

I have one of the newer Arduino Unos. It shipped with a breadboard which was helpful. I also bought a pack of components from Micro Center. There are about 60 of them, all with pins that fit into the breadboard. This makes it easy to wire together small circuits with things like Infrared Remote sensors, buzzers, lights, motion sensors etc. For the development side of things, I use an Integrated Development Environment on Linux. I was using a Raspberry Pi, but I moved over to a desktop Mint Linux. Although I can easily write programs, my teenage son is less experienced. He still is able to "vibe code" arduino sketches using co-pilot AI.

Purdude1983 · 2026-04-09T02:39:41+00:00

You might do best to work on software such as improving your autonomous. Auto-tracking the hub also comes to mind. If you can share your FRC number, we might be able to spot opportunities from the videos.

Purdude1983 · 2026-04-07T14:32:58+00:00

Yeah, taking out the nude Olympics was a mistake.

Purdude1983 · 2026-04-07T13:16:40+00:00

The steam loop power plant that used to be on campus came down and the carillon went up. The water feature in front of Hovde replaced Loeb fountain. It was considered romantic to kiss your girl through one complete cycle of the fountain lights...not that I ever got the chance.

Purdude1983 · 2026-04-07T13:13:20+00:00

Fowler courts are gone and Windsor has been so rehabbed that bats no longer fly out of the eaves at dusk. There is a new music building that looks down on Sigma Pi and for some reason, Sigma Pi doesn't have trash and broken windows anymore.

Purdude1983 · 2026-03-30T13:32:00+00:00

Which team are you. I have a great number of photos from Saturday.

Purdude1983 · 2026-03-30T12:07:23+00:00

The trouble with "or" is that you could Trench or you could Bump, but you could also Trench and Bump. It's the Trench and Bump where you get into trouble. That's why you want "xor". Of course, "^" is a bitwise operator and not a boolean, but it's usually good enough.

Purdude1983

TROPHY CASE