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Sun, 14 Jul 2019

Sensor Problems

— SjG @ 9:28 am

I’m working on a circuit based on a 34685-MP chip bought at Marlin P Jones. The chip is supposed to be sensitive up to 7m away, but I’m not getting very reliable detection. My first thought was that, being next to a bunch of high-frequency stuff (a Teensy 3.2 with the audio shield), maybe it was interference.

The not-yet-functioning Annoy-o-Tron

I tried taking its output to the base of a transitor and lighting a LED to see if that was better. I got similar results.

I’m not sure what’s going on yet. If I do figure it out, I’ll post here.

Update: the Interwebs deliver! Following the recommendation I found in the comments on this article, I put the 34685-MP on a cable, and moved it away from the breadboard. Voilà! It now works as I had hoped!


Tue, 7 May 2019

The Maccabeam™

— SjG @ 5:43 pm

Back in 2017, I laser-cut a menorah out of poplar. When the family showed up for Hannukah, I mentioned my “laser menorah.” My nephew’s eyes lit up with excitement, but I could see his disappointment upon presentation of the actual product.

Subsequently, I’ve been building something closer to what he probably envisioned in the first place.

I’m slow at building things, and have lots of other commitments taking up time. I spend maybe an hour or two a week on the project, and tend to forget a lot of important details between sessions. There is a whole lot of learning and re-learning. However, I thought that documenting the various processes here would be good for me (my external memory), and may be of interest to others.

The first step of any project, of course, is to give it a good name and maybe a logo. Since it’s a laser menorah, I’m calling it the Maccabeam™, and my initial version of the logo looks like this:

The Official Maccabeam™ logo

So there are a lot of things to talk about here. I’ll post a lot of circuit design ideas, physical design ideas, and details on the software that drives it. I’ll also probably post some ambivalent thoughts on the whole holiday of Hannukah1. But for now, I’ll start with the list the requirements I’ve been using for the project:

  1. Instead of candles, I’ll be using lasers!
  2. The lasers will probably be illuminating vials of olive oil rather than shining on the ceiling.
  3. There will be more lights, too. Color LEDs! NeoPixels!
  4. The whole thing will be driven by an embedded controller I can program. Since I like the Teensy and Paul & Robin seem like the kind of people I want to support, I’ll go with a Teensy LC.
  5. Since I have a microcontroller, it should take advantage of the smarts, and not just rely on an on/off switch.
  6. Hey, if it’s gonna be smart, it should use a GPS receiver to figure out the location and date, and automatically run itself on Hannukah.
  7. It will need some kind of display so you can tell what it’s doing, what time it is, how long until Hannukah, etc.
  8. It’ll be cool if it could play some music too.
  9. OK, maybe I don’t want an on/off switch, but I do need a switch to trigger a simulation mode. That way, I can show it off to people at any time of year.
  10. [update 13 May 2019] Oh, I forgot an important one. The Maccabeam™ wants to be stand-alone. It doesn’t want any dependencies on the Interet, wireless networks, or the like. It should only depend on a source of electricity and a constellation of 20-some-odd highly sophisticated satellites and their ground support network.

So with that set of requirements, I got started. I hope to write something here about each of those requirements as I complete the build.

Update 1: The Flickering Candles.
Update 2: Some Physical Structure
Update 3: When Exactly is Hannukah?

1 I mean, it’s celebrating the victory of a family of intolerant religious fanatics over both their foreign imperial enemies and their more moderate coreligionists. Their victory established the shaky Hasmonean dynasty whose infighting and collapse resulted in Herod’s rise to power in the region, etc.


Wed, 2 Jan 2019

Using Makefiles for Teensy Development on Mac OS

— SjG @ 9:24 am

Even if you don’t want to use the Arduino IDE for building your application, or want to do fancy things that only the evil, convoluted syntax of Makefiles can provide, you can do Teensy development on the Mac from the command line. While there are a lot of guides out there on how to do it, I hadn’t seen a complete step-by-step set of instructions.

So with no further ado, here are the steps for building Teensy applications on Mac OS using the Makefiles and the mighty command line.

  1. Download the Arduino IDE from https://www.arduino.cc/en/main/software and install it.
  2. Download Teensyduino from https://www.pjrc.com/teensy/td_download.html and install it.
  3. Download a “basic project template” for Teensy. The original is at https://github.com/apmorton/teensy-template but I’ve been using the fork at https://github.com/a-j-f/teensy-template which has been updated more recently and uses the Teensy CLI Loader for uploading to the device.
  4. Update the Makefile to set your Teensy model
  5. Type make to build, or make upload to install on your Teensy

If you’re wanting to monitor the serial console of your Teensy over USB, install a terminal program like CoolTerm. Alternatively, if you use Homebrew or MacPorts you can use a console-based terminal program like minicom. Once the USB connector is plugged in, your Teensy will show up as something like /dev/cu.usbmodem45504901. The communications settings will be 115200 baud, 8 bit, no parity, 1 stop bit.