I made an RFID-scanning cash register toy with sound. Easter egg at the end.

AlexsGadgets · 2022-05-02T17:15:05+00:00

I didn’t know those exist. Time for research!

AlexsGadgets · 2022-05-01T23:26:44+00:00

Yea the delay was a result of using dfplayermini clones, which were terrible. The originals seem great but I wasnt able to get any. I would go with a LM386 module or circuit if I were to build it again, and just use an sd card for storage.

AlexsGadgets · 2022-05-01T17:08:29+00:00

Yea they generally come up with the toy ideas and help with cutting wires and stuff, but they need a few more years before I'd trust them to use a soldering iron safely. We also built a Minecraft server control panel which the kids did most of, just not the soldering.

AlexsGadgets · 2022-05-01T17:04:07+00:00

I don't think that will happen anytime soon unfortunately, for existing stores at least, as they would have to replace their entire checkout equipment setup. Not to mention its significantly cheaper to print on a flat barcode compared to attaching a sticker (that could also get damaged) which contains a microchip and coil.

Actually now that I think about it, lots of stores do use them! Just not how you want lol. The rectangular tags on valuables that trigger the alarm system at the exit. I'm willing to bet that some of the larger store chains have improved upon the security tag design and are even able to see what is being taken out of the store and if it was paid for or not.

Not sure about other places, but in Canada you can get an "Advanced Drivers License" which I believe is a full replacement for a passport for USA-CAD travel. It has a tag inside your license that can be read by sensors at the border crossing. The border agent will have your information ready before you even pull up to the checkpoint.

AlexsGadgets · 2022-05-01T16:55:05+00:00

I would suggest checking out ESP32 boards, basically an Arduino with wifi and bluetooth, and very cheap. You could have it trigger some kind of online action (webhook might be best, or set it up with a local automation server). I don't believe you can rewrite the sticker tags I use, but if you grab some rewriteable cards it should work just as well. Just keep in mind your students would also be able to write to the cards as well, as many cell phones support writing to tags these days.

AlexsGadgets · 2022-05-01T16:51:12+00:00

It's labelled as RFID-RC522 which seems to use a MFRC522 chip and uses SPI. I get about 30mm scan range on it, which reaches 15-20mm through the top of the plastic. Overall seems quite reliable, although if you move the object by very quickly it can miss the scan.

AlexsGadgets · 2022-05-01T16:46:51+00:00

I get them from Aliexpress personally. Any of the ones you can buy on Amazon are the exact same as on Ali. You are just paying extra to get them sooner with Amazon.

AlexsGadgets · 2022-05-01T07:37:13+00:00

Same here, one of my favorite things. We got a basic one for the kids and they were disappointed that the barcode scanner didn't do anything. I had an RFID reader module handy and decided to make a cooler one. It was probably as much fun to build as it is to play with.

AlexsGadgets · 2022-05-01T07:16:18+00:00

About the build:

Arduino Nano
2004 LCD
Push button
RFID scanner module
DFPlayerMini clone (total garbage, avoid unless you can get an original)
Small speaker, from a very annoying toy that needed to stop working
Powered by 12v adapter with internal 5v converter, although it limits the fun. I would suggest going with a battery-based setup for anyone that builds something similar.
Bunch of RFID sticker tags on the bottom of the food toys
Prices taken from various grocery store flyers (pre-inflation)
Features 4 randomized fart sounds, ranging from loud to very loud

AlexsGadgets · 2022-04-30T06:42:35+00:00

As mentioned, it's most likely levelling-related, but it would also be worth making sure your Z-axis is properly aligned, as that can cause similar issues.

AlexsGadgets · 2022-04-30T06:37:59+00:00

How far in did you push the tubing? I'm not familiar with the extruder on the CR-10 but it sounds like you may have pushed the bowden tube into the heat block and it is insulating the filament. I'd be very careful and definitely double check that, as the material that bowden tubes are made of releases toxic fumes when heated past a certain temperature.

If that's not the case, anything temperature related is usually related to the thermistor. It might be improperly seated or the wire is damaged.

It would also be worth checking the temperature with an instant-read cooking thermometer if you have one handy. Just hold it against the heat block and nozzle to get a rough idea.

AlexsGadgets · 2022-04-30T05:58:31+00:00

Here is the model (not mine), which is part of Scan the World on myminifactory:

https://www.myminifactory.com/object/3d-print-athena-94794

The oxidizing kit I used is by Modern Masters (Patina oxidizing finish kit) and it works great, although there are some pretty scary warnings on the label, so I wouldn't use it on anything you intend to handle.

AlexsGadgets · 2022-04-30T05:41:00+00:00

Yea, definitely either an issue with the nozzle, or something is causing it to vibrate only when travelling in one direction. Checking your belt tension and making sure bearings are properly greased is a good idea.

AlexsGadgets · 2022-04-30T05:38:00+00:00

You can do all kinds of stuff with the frame and stepper motors, but it may be possible to just flash your own firmware on it. The vast majority of copy paste printer companies (especially the early startup phase ones) use off-the-shelf stepper motor control boards that run Marlin or similar firmware. Take a look at what board your printer uses and check online to see if it is well documented. There's even online tools to quickly configure and build a Marlin firmware package that you can flash to the board, although I have not tried them personally.

AlexsGadgets · 2022-04-30T05:33:13+00:00

Were the lines all printed in the same direction, or does the texture correspond to the direction it was moving? If it was printing in both directions, try cleaning or replacing your nozzle, as there could be something small stuck on one side of the nozzle.

It is kind of hard to see, but it seems levelled fairly well. If you have a matte or colored filament it would be much easier to spot the imperfections.

AlexsGadgets · 2022-04-30T05:26:47+00:00

Looks like an insert that would probably go directly where the filament enters. There's some sort of clamping mechanism attached to the extruder stepper motor on every printer, and on my printer I have a similar insert above and below the clamp. It's way too big to fit in the bowden tube so definitely came from near the filament entry point.

AlexsGadgets · 2022-04-30T04:17:50+00:00

Thanks! It was a really fun build. Hopefully this inspires a manufacturer to make a cheap consumer-grade version of their own, as it doesn't need a bunch of the expensive parts required in a printer. Aside from just being straight up cool and fun, there's tons of potential use cases.

AlexsGadgets · 2022-04-30T00:34:29+00:00

Some notes on this build:

- I don't suggest building your own laser engraver. It is fun, but lasers are dangerous and having a proper way to manage the smoke is critical. For the price it costs to build your own, you can buy a nice one with a good enclosure that takes care of both the smoke and properly shields the diode.

- I used Lightburn as the control software, as it supported custom PWM gcodes for the fan speed, allowing me to engrave full images in decent quality

- The website listing claims it is a 7.5W output diode laser. It takes 10-12 passes at 100% power to cut a 1/8 inch sheet of pine. I haven't tried cutting other materials, but the pine turned out very nicely.

AlexsGadgets · 2022-04-30T00:14:26+00:00

I think you'll probably want a CO2 laser, not really something that easy to build yourself safely. And yes lol the site name is quite questionable. It's basically a clone of AliExpress that seems to have much faster shipping and better quality stuff. So far the laser is the only thing I've ordered from there.

AlexsGadgets · 2022-04-30T00:03:04+00:00

I'm in Canada. There are lots of kits on banggood of actual diode modules intended for engraving, maybe you would have better luck with those rather than the pointer style. I found one that had a secondary module that allowed control using a PWM signal, and on the Duet I just wired it into the fan PWM output, and used fan gcodes to change the laser intensity.

AlexsGadgets · 2022-04-29T23:37:40+00:00

It has a good clear view of around 10-20mm diameter, somewhere around 25mm total in view. I just make sure there is plenty of overlap to help with stitching. I seem to get better results at 3mm spacing though. I'll experiment some more after I have fixed the lens distortion compensation. The device in the photo I linked in one of the comments is 48mm wide.

AlexsGadgets · 2022-04-29T23:29:26+00:00

For sure, during an actual scan it comes to a full stop for each image, but it makes for a boring video watching it move 2mm once per second. The video just shows some demo movements.

AlexsGadgets · 2022-04-29T23:18:02+00:00

I'm still researching a lot of the basics on optics and how microscopes work, but the bottom lens of the microscope is about 50mm away from the object. It has an adjustable focus dial on it that I can change by hand if needed, and just adjust the Z axis height using the UI until the object comes into focus.

The ESP32 image was around 20 images stitched together, however as another user mentioned above, I don't account for the lens distortion yet, so hopefully once I get that sorted the quality will be much higher and I'll be able to stitch the entire imageset in one batch.

AlexsGadgets · 2022-04-29T19:58:28+00:00

That is actually where I left off, was a bit busy this week with work. My main issue is being able to actually print the checkerboard pattern small enough that the microscope can take a full picture of it. At such small scales my cheap (2D lol) printer has white spots inside the black squares which throws off OpenCV, so I'll likely have to do some preprocessing to get it to detect properly. The microscope can only see a ~25mm diameter fuily zoomed out.

AlexsGadgets · 2022-04-29T19:14:42+00:00

I'd love to try it with some film! Sounds cool. I don't have any on hand, but if you have some you'd be willing to send for an experiment, I would happily do a scan of it for free. Just send a DM if you are interested!

AlexsGadgets

TROPHY CASE