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Quorten Blog 1

First blog for all Quorten's blog-like writings

Can you mix leaded and lead-free solder on the same board? No.

quorten

2020-04-07

Categories: raspberry-pi  
Tags: raspberry-pi  

Can you mix leaded and lead-free solder on the same board? In general, no. Avoid this whenever you can, because if the two different types of solder ever do directly mix together on the same board, you run the risk of the solder joint becoming brittle over time and cracking, which will then need to be repaired.

Also, please note… that being said, if you are repairing old electronics, please please please prefer to use leaded solder. Future buyers will not like a board that has been ruined by mixing incorrect solder types.

Also, another good point in the discussion on the particular forum I’ve found.

20200406/DuckDuckGo mix leaded and lead-free solder on same board
20200406/https://www.eevblog.com/forum/beginners/mixing-lead-solder-with-lead-free-solder/
20200406/https://en.wikipedia.org/wiki/Tin-silver-copper

Notes on lead-free solder types for your own uses, avoid Tin-silver-copper solder for your own uses, it’s best only for automated assembly. Reworking and repairing with this type of solder is a real pain, prefer to use 99% tin or 100% tin solder instead. Not only is this much easier to work with, but it has also been proven to work well for automated assembly mass production.

Reflow soldering nylon connectors, and using solder paste with through-hole components

quorten

2020-04-07

Categories: raspberry-pi  
Tags: raspberry-pi  

Molex PicoBlade, yes, one of my favorite connectors thus far. Can you reflow solder the header versions of these connectors directly onto a printed circuit board? Most of these connectors are made of Nylon, which is deemed unsuitable for reflow soldering due to its high moisture absorption rate. I searched around on Digi-Key for PicoBlade headers using a different insulation material, but I’ve found nothing. So, is there other information out on the wider Internet about reflow soldering with Molex PicoBlade connectors? Yes…

20200406/DuckDuckGo molex picoblade reflow soldering

According to this Wikipedia article, many JST connectors are made of Nylon and are unsuitable for reflow soldering, though there are a few versions made of a different insulation material that will work with reflow soldering. Ah, that’s not very helpful, other than hinting that maybe it’s not possible.

20200406/https://en.wikipedia.org/wiki/JST_connector

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Simple serial communications, and methods to progressively reduce the pin count requirements

quorten

2020-04-07

Categories: raspberry-pi  
Tags: raspberry-pi  

Here is a quick summary of various means for serial communications and the resulting pin counts.

Different variations of serial communications connectors.

  1. SPI is the simplest type because it can connect straight to a shift register. How many pins? Typically 7 to 8: Ground, 3.3 V, 5 V (optional), RESET, Slave Select, CLOCK, MOSI, MISO.

    If we omit RESET and use power-cycling for RESET instead, assuming the receiver has a power-on-reset circuit, then we can go with only 6 pins.

  2. Asynchronous serial communications. Eliminating the separate clock signal allows for only 5 pins: Ground, Power, Data Terminal Ready (DTE), Transmit, Receive.

    To get to 4 pins, DTE can be eliminated by assuming a bus protocol that transmits that information “in-band,” i.e. software flow control rather than hardware flow control.

  3. Asynchronous serial communications, half-duplex. 3-state logic and state tracking is used to perform transmit and receive on the same conductor. 3 pins.

  4. Multiplexed power and data transmission, “powerline communications.” Data transmission is modulated on the power line. 2 pins.

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The real reason why there is a toilet paper shortage during the Coronavirus

quorten

2020-04-04

Categories: covid19  
Tags: covid19  

Stores and news outlets have blamed toilet paper hoarders for the cause of the toilet paper shortage, but even after stores have placed limits on customers on how much toilet paper they can buy, they are still encountering shortages. Why is this? One of the big reasons not to be neglected is the fundamental shift in where people are spending their time: from commercial settings to full-time at home. As it turns out, toilet paper for the commercial market is a radically different product than the consumer market toilet paper, and it isn’t easy to turn around that excess that is no longer being used at schools, businesses, restaurants, etc. and get it onto retail store shelves. Commercial toilet paper is much more utilitarian and bland, whereas consumer toilet paper is all about bright decorative retail packaging and “special effects” on the actual toilet paper itself.

As it stands, there’s enough tellings about how awful the toilet paper at the gas station is. Yeah, it’s really not that nice, but when you really have to go to the bathroom, it gets the job done.

20200403/https://marker.medium.com/amp/p/c812e1358fe0

Vacuum tubes can be built without rubber vacuum pumps

quorten

2020-04-04

Categories: tour-de-force   computer-history  
Tags: tour-de-force   computer-history  

Vacuum tubes… ah yes, the venerable origin of modern electronics. Diodes, transistors, even resistors in the form of incandescent light bulbs, many important modern electronics trace their roots to vacuum tubes.

So, here’s a question I was thinking about. Exactly how hard is it to build a vacuum tube of your own? When you think about it, it really isn’t that hard. You need glass blowing and a vacuum suction pump. Once you blow glass into an cylindrical or spherical envelope shape, you give it a narrow-necked opening and you connect a hose to that and your vacuum suction pump. Then you pump all the air out to create a vacuum and keep pumping to sustain the vacuum. You can reheat the narrow neck to convert it into an enclosed nipple. Now, you can stop vacuum pumping and disconnect your hose. The vacuum will remain. It’s all simple in concept, it’s just that most modern homes don’t the necessary tools to be able to make a vacuum tube at home.

But, here’s a crucial question to answer. How do you build that vacuum suction pump and hose? Does it require rubber? If it does, then the abilityv to invent the vacuum tube was contingent on the introduction of rubber to the world at large, outside of Mesoamerica. Fortunately, vacuum suction pumps can be built without rubber. Rubber is mainly a convenience in modern designs, but it is totally possible to build a vacuum suction pump without it. In fact, the vacuum suction pump and evacuated chamber in the Magdeburg hemispheres did not use rubber at all. The hemispheres were made out of copper, and grease was used to seal the gap between them to be air-tight. Cork can also be used to seal valves in place of a rubber stopper.

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Beware of diode package sizes

quorten

2020-03-31

Categories: raspberry-pi  
Tags: raspberry-pi  

Recently, I received a purchase I placed on Digi-Key. I looked at the physical size of the Schottky diodes I purchased, and wow, they were big. Not just the diode package, but the wires to the diode itself were too large in diameter to fit through the through-holes on my perfboard. No worries, in all other electrical specifications, they were good for my purposes, I just needed to give them a “surface-mount” style treatment to connect them to my perfboard and all was good.

But, the moral of the story, if Digi-Key doesn’t tell you the specific dimensions of a component but just gives you a size code such as DO-204AC (DO-15), then make sure to look up that standard package’s dimensions and verify the component will fit in the board mounting you desire for it.

Here is the Wikipedia article that lists the dimensions info on the DO-204 standard.

20200331/https://en.wikipedia.org/wiki/DO-204

Note that transistors have similar standard size codes, you should check those to make sure you are getting something that will work well for you.

Hot-swapping connector designs, I2C connector design, my own SPI connector design, and "Stop 'N' Swop"

quorten

2020-03-31

Categories: raspberry-pi  
Tags: raspberry-pi  

So, I’m in the process of designing my own modular SPI connectors for my electronics projects. There is, after all, no real standard for me to copy, so I’m making my own just like everyone else has in times past. Now, I do remember Wikipedia stating some words on this in relation to I2C, what were those anyways?

20200331/https://en.wikipedia.org/wiki/I%C2%B2C

Oh, interesting. Here, the connector design is to prevent power and ground from being connected with reverse polarity in the case that the connector is inserted backwards, as can easily happen with the unpolarized 1/10 inch pin headers common on prototyping electronics boards. Also, in this case, the power and ground are not placed right next to each other, but staggered with data pins in between. This could also help prevent accidental shorts between the power pins. Note that this Wikipedia article mention all comes from the advice of one particular person giving their answer on StackExchange Electronics. So, yeah… it’s not a really widespread thing, as you might see.

Also, the Wikipedia article about hot-swappoing is also insightful. In particular, the idea that you don’t need to add special electronics circuitry to enable hot-swapping, this can all be done through a staggered connector design that ensures some pins make contact before others. In particular, ground pins make contact first, and power pins make contact last. (Staggered connectors were once thought to be an expensive solution, but nowadays it is considered cheap.)

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Lessons learned on designing physical electronics projects, 3D scanner, page counting device, software dependencies, and bill of materials

quorten

2020-03-29

Categories: raspberry-pi   media-prog   pentax-k-1-camera  
Tags: raspberry-pi   media-prog   pentax-k-1-camera  

Electronics projects. One thing about building electronics as a hobby is that people tend to get excited about it because it produces these cool electronic gadget toys. Cool, yes indeed it may be, but coolness aside, there are many practical factors that need to be considered. Over the course of my recent endeavors working with electronics hobby projects, I have found it necessary to summarize some important lessons that I learned, which are certain to be valuable for anyone else to know in advance should they consider picking up such a hobby.

First Question: What is the purpose of your electronics hobby?

First of all, answer this question. What is the purpose you are doing this electronics project for? Many simple electronics projects don’t strictly need to be done with a physical electronics project hardware element. Like any hobby project that requires buying raw materials, the associated costs can quickly spiral out of control if you just want to buy anything that’s fun to play with. But, furthermore, you may find out that electronics is not as fun as you thought it would be if you just buy and build anything you can think of with electronics.

So, it is crucial that before beginning, you present to yourself and answer the question up front: Why can’t this be done purely with software alone? Why is a electronics hardware element actually required?

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Lessons learned on switched-mode power supplies and battery power for the Raspberry Pi

quorten

2020-03-29

Categories: raspberry-pi  
Tags: raspberry-pi  

Switched-mode power supplies for the Raspberry Pi, the ultimate way to get your Raspberry Pi Zero to run off of alkaline AA batteries, right? No, actually it isn’t. The ultimate way is to connect Nickel Metal-Hydride (NiMH) AA batteries almost directly to your Raspberry Pi.

So, what exactly is going on here? The primary problem at stake is the limits imposed by the power consumption of the Raspberry Pi Zero and the current supply ability of your batteries. Despite the Raspberry Pi Zero being considered a “low-powered computer,” it is still a relatively high power consuming device on an absolute scale. Really, 250 milliamps at 5 volts? That’s 1.25 watts of power. Sure, that’s not much power compared to traditional desktop PCs and traditional incandescent light bulbs in wall and ceiling mounted lighting fixtures, but that’s an awful lot of power to draw from AA batteries. According to Wikipedia (and other sites not referenced), a single alkaline AA battery can supply up to 0.5 amps of current before its charge supplying ability starts to sag significantly below its rated charge capacity in milliamp-hours (1400 mAh) or kilo-Coulombs (5 kC).

20200329/https://en.wikipedia.org/wiki/AA_battery

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