« Posts by MadRocketSci

Computers

I’ve been reading a book from a friend on the mathematics of infinity.

It occurs to me that our computers, every last postage-stamp sized little spinner, is at heart a trans-finitist. They believe in the integers, and not even all of the integers, but integers below a certain finite size. Everything else is a construction on top of them. Doesn’t seem to limit us too much from a practical standpoint….

An important Heinlein quote

Heinlein was an uncommonly wise man:

Secrecy is the keystone to all tyranny. Not force, but secrecy and censorship. When any government or church for that matter, undertakes to say to its subjects, “This you may not read, this you must not know,” the end result is tyranny and oppression, no matter how holy the motives. Mighty little force is needed to control a man who has been hoodwinked in this fashion; contrariwise, no amount of force can control a free man, whose mind is free. No, not the rack nor the atomic bomb, not anything. You can’t conquer a free man; the most you can do is kill him.” Robert A Heinlein

On the other hand, force sucks…

Weekend Woodworking Project

Last week I made a trip to Menards, a local midwestern home improvement store. Menards makes Home Depot and Lowes look pathetic. The quality of their wood is also amazing. Actually, I made two trips to Menards. 😛 The first one, then a bunch of woodworking mistakes, then a second trip for more raw materials.

There is a spot in my office that is bare right now that could use a 27″x60″ table jammed in the corner.

I made some plans.

TableProjectDrawing2

I assembled a tabletop (after learning a trick to plane the wood.) Glue joint down the middle. Edges planed together in a vise so that they’ll fit together almost perfectly. The thing was flat enough that I didn’t have to flail around on it with the woodplane.

I then cut those beautiful pine boards (seriously, they’re square, and sanded almost polished until they slide against one another.), measured and glued them down to the tabletop. This makes the frame which hold the legs.

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I ordered four “foursquare” 2.25″x29″ legs from tablelegs.com

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I then drilled and glued down the corners – the hardware pulls the legs against the frame producing a satisfyingly rigid, yet detachable joint.

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I created some V-blocks so I could squarely (more or less!) drill into the corners of each table leg. I inserted a threaded 1/4″-20 brass insert into the wood (courtesy of the local hardware store).

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The table was finally assembled today. Then I quickly stained it and will leave it to dry over the next two weeks.

20190705_162738There are a few small errors in the project which would probably make this unsellable. It is, however, pretty good for a first try, almost professional, and functional. When it finally dries, I’ll furniture polish it and place it in my office – more flat space to clutter up with junk! I mean, to work on.

Need to Blog Again

I need to start blogging again.

But more than that, I’ve been thinking lately about the use of the internet to communicate. I haven’t really been reading my friend’s blogs. Dissapointed to learn that one of my friends blogs at http://raymondscientific.com had gone offline. Hopefully it isn’t entirely defunct. People running their own blogs seems to make for a healthier internet than people using one of some small number of monopoly services as a client. It seems, when people want a forum to contact their friends, they all pile onto facebook or twitter.

The advantages: Everyone’s on there.’As I’ve learned in the past, it’s hard to have an active internet social life on an empty PhPBB forum. If no one is on an IRC channel but bots, then you can’t very easily have a conversation.

The disadvantages: Facebook isn’t a platform that you own or control. You’re putting your personal data and a record of your personal sentiments, as well as detailed information on who you’re friend’s with, how often you communicate, etc in the hands of this company. A company which, these days, seems hell bent on manipulating their users.

The belligerence of the tech monopolies has spawned various movements to produce alternatives. I’m not familiar with most of them, but may investigate later.

I’m going to start looking into doing more with my servers. It seems like in the early internet everyone had their own space/forum/what-have-you going. Popular webcomics all had their own forums. Every hobby on earth had it’s own forum (I remember one that I liked a lot – I think it was run by SEDs or the Mars society.) People owning and operating their own servers and forums seems like a desirable end goal (to me at least, to “people”, who knows?) Maybe if I figure out the ins and outs of some of this I can help by posting tutorials. “How to Internet: 101”.

I’ve tried before to create a dovecot/postfix e-mail server. Past attempts produced ill-configured junk and corrupted package lists. Maybe I’ll try again this weekend. This is apparently one of the more complicated and fiddly parts of setting up server services.

In Ye Olden Days there were mailing lists: Why don’t people use wide-distribution e-mail the way they use a centralized forum like Facebook? There wouldn’t be a forum to censor or shut down, just everyone’s e-mail server forwarding the messages. There would have to be a way to separate “serious/business e-mail” from “friends-and-family spam”, from “everyone else’s spam”. People probably don’t want their inboxes filling up with junk. Maybe a better set of sorting filters could take care of those sorts of problems?

Why do people use Facebook instead of PhPBB style forums?

Why do people use centralized chat services like discord, instead of everyone running their own IRC server?

Why do people use YouTube instead of hosting their own videos on their own servers?

(Monetization – YouTube makes it easy to collect ad revenue. That is, if they like you. If they don’t they’ll abuse you and play head-games with your listeners.)

(I expect there to be reasons in each case: Maybe pointing the way to the development (or re-development, as the case may be) of a less centralized internet.)

This weekend in electronics

All the stuff finally came in to try making my ADC board. Here it is:

The board

The board

The mess

The mess

 

This board is intended to be a general purpose lab DAQ board. Depending on how you set the resistors in the jumper slots, you can sense current, voltage (up to +/- 10V), and set the gain into the ADC and analog output. You can even route the analog output to something else. The way it is designed, it is +/-600V common mode tolerant and has a 130kHz bandwidth. (The main bottleneck being the high voltage differential chip)

 

Other features include:

  • The world’s worst SMD solder job.
  • Mysterious voltage divider behavior.
  • A broken signal generator, so I had to test it with batteries.

:-P. I can fix that. It seems to work though, which is pretty good for my second PCB project.

 

Design Files:

Kicad Files

 

Sequoia National Forest

If you are ever in California, there are a few things you really need to see. When my parents visited in April, we went up to Sequoia national forest. It really is a wonder of the world!

(I only recently got around to posting these, because disorganization:)

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That breakout board, assembled

I managed to assemble one of the breakout boards that came in the mail from OSH-park today. (I screwed up the other two … but 1/3 appears to be assembled and working correctly.)

Here you can see the board attached to an STLink_v2 programmer, with pin PB0 connected to an LED.

STM_Breakoutboard_assembled

Thai Cave Rescue

I hear now that the Thai navy seals have rescued 8 of the children trapped in the cave. Here’s hoping that the remaining children and their coach can be rescued. Good luck.

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Update on 11 July: They’re all out and safe! Hooray.

CNN’s story on the matter.

My First Circuitboard with KiCAD

I made a simple breakout board for the STM32F732 microcontroller. I wanted the pins to be arranged in something like an organized fashion. The pin groups are arranged by name and function (PA0-PA15, PB0-PB15, PC0-PC15, and various control pins.) The STLink programmer should be able to plug right into the top-right four pins to program the controller. The controller should be easily powered by supplying 3.3V and ground to the VCC and GND pins on the top right.

This resulted in a bit of complexity in the routing (which you have to do by hand in KiCAD – no autorouter). I figured out a technique to make it all fit on the board. OSH Park came back with a price of $38 for a minimum run of 3 of these circuitboards. In two or three weeks, I’ll see how well this breakout board works.

circuitboard STM_simplebreakout STM_simplebreakout2

This is part of a proof-of-work that I understand PCB technology, microcontrollers, and PCB CAD software. I’m not an electrical engineer by education, but I’ve picked up quite a bit of it in my work. The KiCAD project files can be downloaded from my site: STM_simplebreakout.zip

PS – yes, I know the ground plane is broken up, and held together by traces. This is my first attempt – I may be able to clean it up a bit in post.

Solder wick

How much solder would a solder wick wick if a solder wick could wick solder?

I still have no idea how to get these things to work …. 😛