Maybe this: www.microchip.com/en-us/product/PCI11400Unfortunately to access the whole datasheet you might have to sign an NDA (and probably have a large company), also designing things with those kinds of interfaces isn’t trivial.
Assuming that there is at least some amount of slippage between the wheel and ground, it seems to me that you’ll need to regularly check the ToF sensors anyway. I’ve found that encoders are fantastic for a lot of things, but not so much for measuring distance because of the problems you’ve described. Perhaps a recurring local check on a reduced set of points to verify location then forward the full cloud less often for further remote processing? It really sounds like you have a tradeoff depending on whether you value accuracy of location or accuracy of wheel rpm (analogous to speed). Using both would give you a nice way to calculate the ideal motor rpm to minimize slippage in a surface agnostic way.
I think mecanum wheels slip quite a bit. So I’m not sure how effective those encoders are. But I’ve only ever tried 3d-printed ones. So I’m not super sure.
You’re sure your STEM students are ready to handle the LiDAR? Manage point clouds, do the arithmetic, path planning etc? We had a practical course with little robots. But they had 3 of those sharp distance sensors at the front and a bumper with a switch. This was enough to teach many concepts and also enough to implement for the students for something that was just a project and not a full time job. But I’m sure that depends on what exactly you want to teach…
And our robots hat the motor drivers (h-bridges) replaceable on socket terminals because every so often someone wasn’t very clever or didn’t listen in the lectures.
They’re university software engineering students, probably a year or two into their degrees. I’m hoping to provide the robots as completed units that are controlled via API, because we’re not likely to get many students with electrical, mechanical, or embedded backgrounds. You’re right about the complexity though, and that’s something I’ve been thinking about – I guess I’ll start out with a bit of optimism regarding their talents, and scale back if needed :D
I don’t really have a scope, budget, timeline, or audience properly defined for this project – in short my client has a STEM program for building and interacting with digital maps, but it’s way too boring and I’m determined to breathe some life into it. So I’m going to have to play a lot of things by ear.
Well, kids / young people / students will surprise you anyways. No matter what you planned ahead. I think teaching this way just requires you to stay flexible and try things with the students and see what works. University students will benefit from a little challenge, but it shouldn’t be impossible and get them frustrated. I’ve never taught myself, but I bet it’s difficult to hit that balance.
Programming little robots is awesome, though. I think it’s on a whole other level to see robots move and do tasks, than to look at your screen and program something that changes a few pixels there. My university course was more related to embedded devices and closer to the electronics. It teaches you valuable lessons when forced to interact with some electronics, real-world physics, constrained resources and you need to get your maths right. Usually students are concerned with something like Java, learning object-oriented programming or handling some big frameworks. Or learning maths. And robotics teaches you to really pay attention, combine different skill-sets and do things without an easy route available.
Maybe it’s just me who likes electronics too much. But I’m sure the kind of motivation you get by watching a real robot move and it runs your code, is unique. And kind of universal. You can do this in pre-school or in university to spark their imagination and motivation.
Your task is a bit different. If you’re teaching something like simultaneous localization and mapping and the students also have to deal with all the robotics, sensors and real-word problems, this might be more of an ordeal for them than fun. Even dealing with noisy sensor values is a hassle until you get to grasp the bigger picture.
If you’re giving them access to an API, you can choose and adjust what kind of abstraction you’re providing them. Give them something high-level or have them do more work. You could prepare most of the implementation and adjust the level of detail while teaching. Maybe skip something and give them working code via your API so they can focus on the problem they’re actually supposed to learn. You can also do it the other way round. Let them start with all low level stuff handled for them and learn the big concepts. Then let them dig down and see what your API functions have abstracted away until then. This way around you won’t run out of time.
I’m sure including actual robotics is going to get them more motivated in contrast to running a simulation.
Haha, I know exactly what you mean – I’m most interested in resource-constrained embedded systems. I like the attiny10 a lot. At work I mostly write Python, but in my own time it’s mostly assembly language. It feels more concrete, every decision matters, and anything that goes wrong is 100% your fault as there are relatively few bugs at that level. It’s a lot of fun. Also the datasheet is very good.
I’m self-taught with all the electronics stuff, I paid for it by teaching a course on whatever thing I did most recently. Then I’d use the proceeds to buy tools and parts for the next big (often dumb) idea. I’d also ask for the software engineering assignments from colleagues in those programs, and complete them in my spare time. It was puzzling to a few people why I would want to do assignments, and indeed some were very boring (oh god Java + Spring framework) but others were quite interesting (formal study of algorithms). Sadly, economic reality kicked in and I had to run a company instead of pursuing my education further (I still try to do one ridiculous engineering thing per year though).
I guess there’s a real risk (…like 100%) that I overestimate the motivation students have – so I think I’m going to take your advice and set the level of abstraction with something API-like to abstract away the low-level components (this is closer to my client’s domain). I’m imagining a robot that acts as a WiFi access point, and having something “like an API” that works over UDP packets that describe high-level functions. Then start with something simple – like a digital map with known starting location, and a small obstacle course that can be completed with simple distance measurement, no point clouds. If that goes well, I can develop towards more complex material – probably not full SLAM, but maybe localization on a pre-mapped surface. I have plenty of my own code as examples of how to do simple UDP communications in Python, I could expand it into a custom library.
Sort of like Logo from 1983, but with a physical robot and sensors. I’m a little to young to have used Logo, but the computer lab in my school was really outdated so I got to try it once :D
Well, there’s also turtles to program in Python (i think) and there is Scratch.
I guess there’s a real risk (…like 100%) that I overestimate the motivation students have
Definitely sounds like it. But a motivated teacher is a very good thing. Maybe you’re able to get that spark across to some of the students.
API-like to abstract away the low-level components
You can always have some extra assignments ready, just in case someone is curious and wants to do/know more. A room full of studens will have a mixed amount of knowledge, abilities and motivation anyways.
I’m most interested in resource-constrained embedded systems. I like the attiny10 a lot.
I also ate a few books and datasheets on the Atmel chips in my lifetime. Their design is well-thought-out and probably an excellent subject to learn the concepts about microcontrollers.
As of now I like the ESP32. It is ridiculously overpowered if you’re used to something like the ATtinies or old ATmegas. With (at least) 520kB of RAM, two cores that work at 240MHz (depending on variant) and very nice peripherals. Also WiFi connectivity is really useful. But it definitely adds to the fun if you programmed the more constrained (previous generation of) microcontrollers and know how spoiled you are and can feel like a supervillain wasting hundreds of kilobytes of memory deliberately. Or (ab)use some of the peripherals for things that wouldn’t be possible with the few timers available on the Atmel chips. Or do trigonometry at crazy frequencies for your robots, because you can handle 32bit floating point numbers. But I’d agree, that doesn’t teach you the same things if you can do floating point arithmetics for cheap and don’t know if calculating a square root is an easy or difficult thing to do. The STM chips also have nice peripherals. But I haven’t really fiddled around with those.
Definitely hope you’ll have fun being involved in that STEM program.
I’ve also messed around with the ESP8266 and various models of ESP32. Their WiFi time-of-flight stuff is interesting. I’ve quite a few projects with both actually! My main complaint is that the GPIO don’t behave nicely (also the esp8266 is a power hog and reboots if you screw up the network stack). They are much slower than I’d expect, and have weird states on boot. It’s not too bad to work around this stuff, but I chose the Pi Pico W so as not to have to explain it.
It still blows me away that I can easily do public-private key encryption on the ESP32. And graphics. At the same time!
Even though you add encoders on the wheels it’s still an open loop locomotion method, you need the room to have a feedback of the position on the plane/in the space
www.iloq.com for example does a lot of parasitic energy stuff. Most of the advertised things now seem to be RFID, but I think they also had locks that are powered by the key insertion.
There’s plenty of places where infrastructure power is not available and a flat battery would be a disaster. Door lock is one mundane one. Space is one more extreme one.
You likely aren’t going to get enough energy to make up for the losses incurred when boosting voltage to 4.2 volts or whatever your battery requires. There’s tons and tons of scam devices out there in the world that attempt to convince people these devices make sense, but they really aren’t usable for anything meaningful.
Charging a battery with a couple microamps per hour. Would probably negates things like self-discharge? But certainly wouldn’t recharge a battery that you have in use with a device. And if that device has radio or storage attached to it, you definitely aren’t gaining enough electricity.
A few years back some farmer living in Droitwich, England (where the Radio 4 longwave transmitter is situated) lit his barn by connecting an antenna to fluorescent light tubes.
It worked, but also created a "not-spot" in the radio reception which the BBC really didn't like (its part of critical national infrastructure!) - officers from Ofcom turned up at his door, made him take the lot down and ordered him to use more "normal" power sources..
A couple things stick out in your story. first off, there’s no such thing as a “not spot” when it comes to radio. That’s not how RF energy works at all. Second, zero news stories show up when I search for such a story. So my guess is that this tall tale has spread in legend form and relies on people not realizing how radio signals work.
I’m skeptical of the “not-spot” claims here. This would suggest that radios also create “not-spots” when being tuned to as well, or that somehow the florescent light tubes were able to “pull” more electrons from the air that were destined to other radios.
Yeah, exactly. This isn’t how radio signals work at all. This is a tall tale and never happened. When I searched for such a story, none came up. When I removed the location and searched for the same type of story, thousands of them are floating around the internet. Powering military tents from radar emissions, powering homes from radio tower emissions, all of them are re-tellings of stories someone once heard from the 1930s, 1940s, and so on. They’re effectively chain letters for the confused.
@rarely a radio receiver uses much less of the power than lighting up the fluorescent tubes would (it wasn't just one lamp) and this incident happened close enough to the TX that it could upset the SWR of the transmitter output stages - if it /was/ possible to do this without creating problems elsewhere then every tall transmission tower would use the RF to power their aircraft warning lamps rather than a separate power supply...
That is the most plausible explanation I have heard but I still have questions. Say there’s an MW tower down the road and I have a 160m tower in my backyard. If I understand correctly, my tower may cause the signal coming from the AM tower to be re-resonated back to the AM tower so the AM tower needs to be detuned. But say I want to harvest the signal and I have tuned my tower to be resonant with the AM tower. Maybe in this case the SWR reading at the AM station is different because it is getting some of that re-radiated power back, and maybe the radiation pattern of the am station has changed slightly, but wouldn’t the main AM tower cover any gaps just like how waves spread out in the double slit experiment once they hit my resonant tower?
I get that a tower excites another tower, and I can understand that the AM engineers will likely hate me, but I don’t understand how radio reception could be affected. If anything, I might have made the station more directional (like a reflector in a yagi) but probably not.
@rarely if you are /that/ close to the antenna an extra tower, or any large amount of metal making the station more directional will definitely be unwanted, both by tradio station engineers and the Communications Ministry (licenses often require a particular directional pattern). But this is more an issue with LF and MF where waves are larger. At UHF/SHF frequencies for wifi harvesting could work but at present the component count required makes it less viable than other power sources.
It may surprise you to know that in the US as a ham, I have the legal right to hoist an antenna or build a tower so long as it doesn’t fall on a power line.
But even then, I don’t think this setup will create nulls. Say the antenna is 400 meters away which I think is still in the far field but I could be wrong. Even if I erected an almost resonant tower (160m) and assuming the regulatory bodies gave me the permit to do so, assuming it’s not powered and simply is resonant, maybe the radiation pattern changes but not so dramatically that my neighbors on the opposite side of my antenna (from the tower) will get poor reception.
Is the direction of the radiation pattern changing what was meant by the “not-spots”?
@rarely the historical reports of issues I've read about are from mid-late 20th century in areas near high power LF/MF stations that would be in the nearfield - from the Wiki article
> absorption of radiation in the near field by adjacent conducting objects detectably affects the loading on the signal generator (the transmitter).
so it would be noticeable, and viewed as an undesirable thing. Harvesting (small) amounts of power in the far field would not cause issues.
@rarely Temporarily lighting small lamps from nearfield RF with a TX power of some kW is definitely possible, a family friend who was the engineer at Radio Caroline in the 1960s did it on board the ship as a demonstration to visitors; but didn't use any antenna nor leave the lamps around to light up the deck (it would have created hassle with unwanted stray RF, and there was plenty about already!). Its not common these days as TX sites are designed to keep people out of the nearfield for safety.
@rarely the claims of "poor reception" caused by "large scale" nearfield power harvesting are from Communications Ministry officers from some decades ago (I mistakenly referred to modern Ofcom rather than the British Post Office which investigated these things until the 1980s), it is possible they just wanted to discourage this practice for the safety of those involved whilst not also opening a can of worms about human exposure to RF (it was Cold War era and much info was classified)
Hold the phone! You’re telling me now that the government lies to people?!
I have also heard of this tale of “not-spots” but have found no evidence myself. The SWR and near field antennas stuff you mentioned makes a lot of sense, I just didn’t understand how I could be stealing electrons meant for others. I mean, if it worked that way wouldn’t trees also creat not spots, especially if they get to a certain height?! Anyway, thanks for the info, and… 73?
@rarely if the link below federates correctly, here is a receiver that uses just the power of the signal, but from a 4kW transmitter 32km away there are only a few tens of milivolts, enough to be amplified by the line in of a desktop PC to listen to the audio but certainly not enough to light any lamps (even an LED). Maybe I could light an LED from our wifi signal close to the access point, but I don't have any RF detector diodes to hand that work at 2,4 GHz
However I would be interested to know where I can earn more abt the topic of electronics, I am very interested in learning it and it would be nice to get some guidance. ty in advance
I… Don’t actually know, I’ve just cobbled together information over the years. My dad worked in an electronics workshop but never taught me anything. There’s a good intro to electronics course on udemy and if you’re serious about it, try get the book The Art of Electronics, its like an electronics bible.
and on top of that, various amateur radio pages, some are indexed in dxzone.com
there seem to be two hard limits on antennas in general. one is for approx lossless antennas that are large compared to wavelength: gain, beamwidth and size are related through diffractive limit en.wikipedia.org/wiki/Diffraction-limited_system it’s really about capture area, which is intuitive for things like parabolic reflectors, but for things like yagi antennas there’s some defined capture area that ultimately depends on their length
the other one is on non-directional antennas that are small compared to wavelength. basically one good antenna that you can make is halfwave dipole, you can try various trickery to make it smaller, but this comes at a cost of either smaller bandwidth or increased losses, or both to lesser degree. it might make sense to make an antenna with 70% efficiency which is 3x smaller for example. it all depends on precise requirements
at the end of the day the most important material in any antenna are tradeoffs
Hey, I am not 100% sure but from other screens i have seen it is probably to boost power. One of the open source ereaders has a little chip that is similure. It is probably a spi display. Do you have the model number of the panel?
I don’t have model number and there are zero indications to who manufactured it. I added a picture of the backside. That’s everything readable on the panel. Nothing else.
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