So, for the Raspberry Pi 3D scanner, camera, measuring device, etc. The verdict is clear. I will be using an optical viewfinder on the camera when I need to see what the camera sees. Now, the problem just comes down to where to buy the part? Well, you can’t really buy a readymade part for this purpose. Your easiest options are to scavenge the optical viewfinder from a point-and-shoot camera or build your own optical viewfinder. After some tough searching, after failing, with the fist idea of searching for a readymade device, I found a great site that has this nice lens search tool for finding precisely the lens you need, without needing custom manufacturing. Otherwise, that was the second best option when you need a very specific lens size and focal length, but all else equal being plastic.
20181019/DuckDuckGo build your own plastic lens
20181019/https://digital-photography.wonderhowto.com/how-to/howto-build-your-own-camera-lenses-0118179/
20181019/https://www.diyphotography.net/build-your-own-lenses/
20181019/https://www.surplusshed.com/
BUT, beware. So I did a search on their site, and although you can get lenses alright, there don’t appear to be any markings on the materials of the lens. Plastic? Glass? I don’t know.
Also, there are other interesting parts on there. LCD for a Sony rear projection TV for only $18? How, you could make a pretty spiffy digital video projector with that! If only you could figure out the signaling on that cable, that is.
20181019/https://www.surplusshed.com/pages/item/L14553.html
20181019/https://www.surplusshed.com/pages/item/L14552.html
Now, let’s look for JST connectors. Ut oh, wait. A JST connector is not actually what I thought it was, upon closer inspection. So, I found this very Sparkfun page on electronics connectors, and now it is clear that I am looking for a crimp connector.
20181019/DuckDuckGo internal small electronic connector types
20181019/https://learn.sparkfun.com/tutorials/connector-basics/all
20181019/https://www.sparkfun.com/news/2328
Now, pin headers or no pin headers? Well, it turns out many hobbyist buyers are preferring pin headers.
20181019/https://www.sparkfun.com/news/2027
This is a really interesting and also risky method of removing pin headers. Cut the pin header plastic apart, remove the plastic heads, use the soldering iron to liquify the solder, then slap the board against the table, briskly but not too rough. The solder and pin will come flying out, and you must also be careful wear goggles and cover skin given the associated risks of the dangerously hot solder, though it does cool quickly.
20181019/https://www.sparkfun.com/tutorials/339
Wow, now this is interesting. Cutting edge technology, neutrino detectors, Iridium satellite communications, and other cool stuff. But, the economic risk involved in stocking these products. Who will use them? Hou could a neutrino detector be useful to most people? Why would people want to use satellite communications when cellular communications will work just fine and be much cheaper?
20181019/https://www.sparkfun.com/news/2025
Okay, now for LCD digit displays? In short, find them on Digikey. Beyond that, I found some other useful tutorials. Oh, and there’s lots of advertising for pairing those full LCD graphics displays with a Raspberry Pi. There are the character-style displays, but I want to avoid that as it is unnecessary complexity for my use case. Typically you will need controllers for more complicated screens.
20181019/DuckDuckGo raspberry pi lcd screen chiclet key calculator face
20181019/DuckDuckGo raspberry pi calculator lcd screen
20181019/DuckDuckGo raspberry pi digit lcd screen
20181019/DuckDuckGo raspberry pi 7 segment lcd screen
20181019/DuckDuckGo 7 segment lcd module
20181019/https://projects.drogon.net/7-segment-led-display-for-the-raspberry-pi/
20181019/https://www.modmypi.com/blog/how-to-drive-a-character-lcd-display-using-the-raspberry-pi
20181019/https://pimylifeup.com/raspberry-pi-lcd-16x2/
20181019/https://averagemaker.com/2014/05/raspberry-pi-7-segment-display.html
This is one of the companies that does custom LCD display manufacturing.
20181019/https://www.displaytech-us.com/7-segment-lcd-displays
Now, what about the Zero Phone, the mobile phone designed around a Raspberry Pi Zero? This uses a graphics-style monochrome LCD screen. The keyboard is buttons soldered onto a PCB with a microcontroller to send signals to the Raspberry Pi.
20181019/DuckDuckGo zero phone
20181019/https://hackaday.io/project/19035-zerophone-a-raspberry-pi-smartphone
NOTE: You were asking what a “mega” is in relation to multiple serial connections for a Raspberry Pi? They must have been referring to an Arduino Mega (ATMega microcontroller), not an IOMega or anything more esoteric.
20181019/DuckDuckGo raspberry pi calculator keyboard
20181019/https://raspberrypi.stackexchange.com/questions/5007/using-an-old-laptop-keyboard-with-raspberry-pi
Now, this is really interesting. NumWorks calculator? It uses a nice fast ARM CPU, a 320x240 color LCD screen, and a rechargeable lithium-ion battery. Also, it can be programmed in Python. But that’s not all: the design and software source code are extensively and openly published too. Curiously, though, it doesn’t have very much more RAM and flash memory than the older TI graphing calculators that came before it. On the other hand, it is a wholly open design. Interestingly, there isn’t a Wikipedia article on it.
Now, NumWorks features Apple-style site design and box design, and plenty of views of Apple devices on their site. So, you kind of get the idea of the intended customer of this product, even though the price point, at $100, is not much different from the TI calculator offerings. On the TI calculator side, the newer models are also sporting higher resolution color screens and faster CPUs, though still not ARM and Python.
Yeah, so the NumWorks calculator does a good job of making it look better than it actually is on first sight. If you take a spin through the online simulator, you will find out that the calculator’s Python is still very far aways away from a true Python installation. Also, interestingly the calculator does not run Linux, but uses an extremely compact stripped down kernel.
20181019/https://zardam.github.io/post/raspberrypi-numworks/
Wow, so reading that article, some important points about Raspberry Pi Zero need to be stated. Important!
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You actually can run a Raspberry Pi Zero off of only 3.3 V… actually, all the way down to 2.8 V. Matter of fact, that’s what the ARM-based NumWorks runs off of all of the time, and it works just fine. Note that this only applies to the plain version, or the Zero W with Wi-Fi disabled. Wi-Fi will bump the voltage demands above this limit.
So, how exactly do you power off of only 2.8 V? Do you wire directly up to the CMOS 3.3 V power pin? Well, well, if the author of this article was true to his mistakes, then you would see that there is an unused solder joint on one of the 3.3 V pins in one of the photos. So, looking carefully, this actually isn’t the case. That must mean that the 2.8 V power is being fed in from the 5 V input. And, according to further sources that I have cited later, this works because the regulator to step down to 3.3 V is a linear voltage regulator, not a switching one. So, there will be no weird signal boosting dynamics. As for the 5 V devices, you simply don’t use them (HDMI and USB hub), so the fact that they don’t get sufficient power is irrelevant.
Please note that other sources recommend that you never wire a power supply into the 3.3 V pins, lest you damage your board.
No, really, why does 2.8 V power work okay? Indeed there is a 1.0 V to 1.1 V voltage drop through the 3.3 V voltage regulator, but the processor itself only needs to run off of 1.8 V, which is just in the usable sweep spot. So, this also means that if you are running off of only 2.8 V, you’re also not intending to use any devices that require 3.3 V power either.
As for the VDD_BATx pin on the BCM2835, it doesn’t actually do anything useful as far as a Raspberry Pi is concerned.
Again, I reiterate, because this is important! Check out the Raspberry Pi 3 B+ power supply article, because that article has some great details on the workings of the power supplies of older Raspberry Pi models too.
20180821/https://www.raspberrypi.org/blog/pi-power-supply-chip/
20181209/https://www.exar.com/product/power-management/universal-pmics/universal-pmics/mxl7704-
Yes!!! It is in fact possible to power a Raspberry Pi Zero with only a 3 V power source, two AA batteries. Yes, just like the original handheld Gameboy consoles, no need for weird three or four battery configurations unless you don’t know what you are doing.
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Unfortunately, the new MxL7704 PMIC used on the Raspberry Pi 3 B+ has a minimum input voltage of 4.0 V. This is not an issue for now as it is not being used on Raspberry Pi Zero boards, but it’s something to watch out for in the future. If future Raspberry Pi Zero boards start using that PMIC, they’ll loose the ability to run off of 2.8 V input.
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You can connect displays to a Raspberry Pi Zero with quite the ease, actually. You don’t need the DSI/MIPI connector available on the Raspberry Pi A+/B+ to easily connect an internal display, nor do you need to use up a whole lot of GPIO pins. And SPI-connected display will work just fine, at least for 320x240 resolution with 18-bit color, maximum 60 Hz refresh rate. Of course, for a handheld calculator-like device, you probably don’t need to or want to exceed that resolution very much.
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Other ways to disable HDMI port power. The easiest way to do this is through a boot option:
hdmi_blanking=2.
20181019/https://en.wikibooks.org/wiki/Unofficial_Guide_To_Expanding_Your_Numworks/Getting_your_development_environment_set_up
20181019/DuckDuckGo NumWorks
20181019/https://www.numworks.com/
20181019/https://www.numworks.com/why/
20181019/https://www.numworks.com/specs/
20181019/https://en.wikipedia.org/wiki/TI-89_series#TI-89_Titanium
20181019/https://en.wikipedia.org/wiki/TI-84_Plus_series
20181019/https://en.wikipedia.org/wiki/Zilog_eZ80
Yeah, so about that Raspberry Pi Zero power trick. Now, that is a really obscure trick that almost no one else on the web has figured out. But indeed, there are plenty of people who would prefer to power their Raspberry Pi Zero off of a 3.3 V battery pack, they just haven’t quite figured out the trick and are still 3 V to 5 V boost converters.
20181019/DuckDuckGo raspberry pi zero 3 v battery power
20181019/https://raspberrypi.stackexchange.com/questions/32601/power-with-batteries-on-3-3v#40312
20181019/https://www.modmypi.com/blog/running-a-raspberry-pi-zero-from-an-aa-battery-pack
20181019/DuckDuckGo VDD_BATx BCM2835
20181019/https://developer.qualcomm.com/comment/11688
20181019/https://www.raspberrypi.org/forums/viewtopic.php?p=326812
But for sure, the good news is that the boost converter can be very small and compact if you make sure to shop for the right one. But, for sure even at 3.3 V, you will still need a boost converter if you are powering from Nickel Metal-Hydride rechargeable batteries.