Autoshutdown Code Modded to hybrid-sleep and allow required restarts

Hybrid Sleep Code

I decided to use hybrid sleep instead of a suspend. I have been using the code for autoshutdown as both autoshutdown, using the shutdown command and suspending. A server that I have been using for a year now supports suspend and I have used systemctl suspend successfully with it. But, if the power goes out, the next time it is as if it was shut down and gets a fresh boot. The way around that is to use systemctl hybrid sleep which puts the RAM content into swap and then suspends. This way if the power goes out it will just resume from hibernate.

Reboot code

After setting up the machine with hybrid sleep. I realized that the mechine needs a reboot once and a while after unattended updates and thought that it would be nice to automate that process. I looked on line and found a piece of code that will reboot the machine if a reboot is required. This is done via detecting the presence of the reboot-required file. So far testing once today 8/12/2017, OK so far!

https://muffinresearch.co.uk/how-do-i-know-if-my-ubuntu-server-needs-a-restart/

Snippit of code added to autosuspend a.k.a autoshutdown code that was covered in the original post on this topic

# If the reboot-required file is present, restart and l$
 if [ -f /var/run/reboot-required ]
 then
 logit "RESTART REQUIRED"
 echo 'Restart required' >> /var/www/html/shutdown.txt
 date >> /var/www/html/shutdown.txt
 echo "------------------------------------" >> /var/www$
 systemctl reboot
 fi

# Fall through and hybrid-sleep it!

systemctl hybrid-sleep
 # Switched to hybrid-sleep 08122017 systemctl suspend
Shadowbox for 7490 Clock

7490 TTL Digital Clock Housing

After a few months of testing ( April – June 2017 ) the 7490 TTL decade counter chip based clock out with the newly added OCXO it was ready to be mounted in a housing.

7490 TTL Clock with OCXO under test
7490 TTL Clock with OCXO under test

Monitoring it against an accurate timebase ( Linux PC with NTP ) while piled up loosely on a small table in the office, it was running good and steady. No flaky counts, no flaky digits that were not lighting or staying lit when they should not be.

 

 

 

Consolidating Power

After the photo was taken above,  the power supplies for the clock were consolidated. Under testing it was powered by 2 wall supplies, 5V for the TTL chips and 12V for the OCXO. For the final version I used a 7805 regulator on the right hand side board to down regulate 12V from a Radio Shack 12V/2.3A power supply to 5V for the TTL chips. I got lucky and spotted the power supply during the last few days that Radio Shack was still in business in April 2017.

Wood Housing

Not having a good set of tools on hand to build a metal housing, a good option was a  wooden one. Micheal’s craft store had both the base that the boards were mounted to and the shadowbox. Both were unfinished and reasonably priced, I believe $5 for the board and $12 for the shadowbox in 2017.

7490 TTL Clock Circuit Board Base
7490 TTL Clock Circuit Board Base
7490 TTL Clock Shadowbox, cover removed
7490 TTL Clock Shadowbox, cover removed. A bit larger than is needed but, it works fine. The glass cover was removed in preparation for sanding and the application of linseed oil.

The base was drilled out to recess fit 10mm standoffs. Holes were drilled for the M3 screws and then countersunk with a larger bit to accommodate the 10mm standoffs. Once again I made out good at the Radio Shack closeout and got a bunch of standoffs.

Subassembly

7490 TTL Clock Mounted on Base
7490 TTL Clock Mounted on Base

The clock mounted on the base in a state of readiness to drop into the shadowbox as a subassembly. This trick is a bit that I learned from working in manufacturing in the past. To make things efficient and serviceable it was common to mount boards on sub assemblies and then mount the subassembly into a piece of machinery.

 

 

 

7490 TTL Clock Mounted in Shadowbox
7490 TTL Clock Mounted in Shadowbox

 

Finally the subassembly gets dropped into the shadowbox and is held in place by four small wood screws that are on the back.

Previous post in this series

7490 TTL Clock Final Housing
7490 TTL Clock, Final Housing

 

 

TTL 7490 BCD

7490 TTL decade counter chip in action

While in the process of working on a digital clock that I built in 2007, I had to take another look at how a 7490 decade counter works in order to remind myself. I rigged one up with some LEDs to count 0 to 9, showing the count in BCD form on the LEDs.

The oscillator used to drive the 7490 counter is one stage of a 7414 Schmitt Trigger inverter. Using a 47 microFarad capacitor and a 15K resistor, this gives a slow enough pulse to watch what is going on at a calculated period of 0.588 seconds. It is basically running the 7414 as a relaxation oscillator, charging and discharging the capacitor through the resistor repeatedly. Being an inverter the output of the 7414 will be high when the input is low and vice versa, so it is always either charging or discharging the capacitor. The waveform, even though I don’t have a scope to put on it, at the capacitor must be a sawtooth I imagine.

Circuit Diagram

7414-7490-diagrams
7414 and 7490 Diagrams: Click on to enlarge

Video of 7490 Counting

The 7490 is both a divide by 2 and a divide by 5 counter. To get a divide by 10, the divide by 2 at Q0 is fed into input B. Outputs Q0,Q1,Q2 and Q4 are weighted by 1,2,4 and 8 respectively. I have the laid out in descending weight from left to right on the board. All set and reset lines are grounded. It will freely run from 0 to 9 and around and around. These lines could be fed into a 7447 7 segment display driver and that would drive digits like a real clock if desired.

The small LED on the left is connected to the output of the 7414 and blinks at the output frequency of it, the jumbo LEDs count from the output of the 7490 and the tiny LED to the right is just strapped from power to ground with a dropping resistor to show that the board is powered. There are also two capacitors 0.1 and a 0.01 microFarad strapped from power to ground to bypass an high frequency switching that appears on the power rails, always a good idea to bypass, this is a good idea on every chip if possible. This eliminates  high frequency noise on the power supply rails. Also grounding unused inputs on the 7414 or any chip that you might use is a good idea to prevent noise and erratic behavior of the circuit.

Powered at 3.5V

3.5VDC
3.5VDC

The usual 5V power supply was tied up running the TTL Clock I built while testing it, so for this setup I grabbed a 3.5V supply. The TTL circuits seem to run fine at this voltage, the only thing is that the time constant is probably a bit shorter for the capacitor to charge and discharge.

More on the 7414

http://www.talkingelectronics.com/pay/BEC-2/Page49.html

 

7490 Clock Article from 2000

I finally found the document that I based the 7490 clock that I built off of. Nothing like the process of moving to uncover lost items. The clock that I built had one main variation in that it did not use the 60Hz from the wall as a frequency reference. Instead it used a series of 7490 chips to divide down from 10 MHz to 1Hz to drive the clock portion. I did this with the foresight that at some point I was going to use a good crystal oscillator such as a TCXO, temperature compensated crystal oscillator or an  OCXO, oven controlled crystal oscillator. These are readily available in 10MHz versions. Another plus is that WWV out of Fort Collins Colorado transmits on 10MHz using a signal derived from a cesium oscillator so the oscillator can be checked and calibrated ( mostly ) against their signal easily by using a shortwave receiver.

I was able to scan the original document  and OCR it back to an electronic copy and published the text with the diagrams on this post. The original scan is at the bottom of this post. I downloaded it in 2007 from the How Stuff Works site. Unfortunately the well written article has disappeared from the Internet entirely or I would have just provided a link to it on this site. So I have put it up here for reference for anyone curious or wanted to build a clock out of 7490’s. If this article reappears on-line, I would just link to it. If someone sees it somewhere let me know.

Circuit Diagram

Here‘s a circuit diagram tor the power supply and time base.

power-supply
power-supply

As we saw in the article on electronic gates,the power supply is the most difficult part.

 

 

 

To create the rest of the clock you will need

  •  At least four 7490 or 74LS90 chips
  • At least two 7447 or 74LSA7 binary to 7—segment converters
  • At least 20 resistors for the LEDs in the 7—segment displays ( 300 ohms would be
    fine.)
  • Some normal LEDs
  • At least two common-anode (CA) 7—segment LED displays (Jameco; part #172088 is
    typical)
  • Breadboard, wire. etc.
7490-pinout
7490-pinout

 

 

 

 

 

The 7490 is a decade counter. Meaning it is able to count from 0 to 9 cyclically, and
that is its natural mode. That is QA, QB, QC and QD are 4 bits in a binary number, and
these pins cycle through 0 to 9, like this

QD QC QB QA
 0  0  0  0
 0  0  0  1
 0  0  1  0
 0  0  1  1
 0  1  0  0
 0  1  0  1
 0  1  1  0
 0  1  1  1
 1  0  0  1
 1  0  1  0

You can also set the chip up to count up to other maximum numbers and then return to
zero. You “set it up” by changing the wiring of the R01,R02 R91 and R92 iines. If both
R01 AND R02 are 1 ( 5 volts ) an either R91 OR R92 are 0 ( ground ) then the chip will
reset QA, QB, QC and QD to 0. If both R91 and R92 are 1 ( 5 volts ), then the count on
QA, QB, QC and QD goes to 1001 (9). So

To create a divide-by-10 counter, you first connect pin 5 to to +5volts and pin 10
to ground to power the chip. Then you connect pin 12 to pin 1 and ground pins 2,3,6 and
7. Run the input clock signal ( from the timebase or a previous counter ) in on pin 14. The output appears on QA, QB, QC and QD. Use the output on pin 11 to connect to the next stage.

To create a divide-by-6 counter, you first connect pin 5 to to +5volts and pin 10
to ground to power the chip. Then you connect pin 12 to pin 1 and ground pins 6 and
7. Connect pin 2 to pin 9 and pin 3 to pin 8. Run the input clock signal ( from the
timebase or a previous counter ) in on pin 14. The output appears on QA, QB and QC. Use the output on pin 8 to connect to the next stage.

Creating the Second Hand

Knowing all of this, you can easily create the “second hand” of a digital clock. It looks like
this

seconds-count-using-7490
seconds-count-using-7490

In this diagram, the top two 7490s divide the 60-Hz signal from the power supply down by a factor of 60. The third 7490 takes a 1-Hertz signal as input and divides it by 10. Its four outputs drive normal LEDs in this diagram. The fourth 7490 divides the output of the third by 6, and its three outputs drive normal LEDS as well. What you have at this point is a “second hand“ for your clock, with the output of the second hand appearing in binary. If you would like to create a clock that displays the time in binary, then you are set! Here is a view of a breadboard containing a divide-by-10 counter. a divide-by-6 counter and a set of LEDs to display the output of the counters in binary.

 

Displaying the Time as Numerals

If you want to display the time as numerals, you need to use the 7447. Here is the pinout
of a 7447, as well as the segment labeling for a 7—segment LED.

7447-pinout
7447-pinout

You connect a 7447 to a 7490 like this

Provide +5 volts on pin 16 and ground on pin 8 to power the 7447 chip
Connect QA, QB, QC and QD from a 7490 to pins 7, 1, 2 and 6 of the 7447,
respectively.

Connect 330-ohm resistors to pins 13, 12, 11, 10, 9, 15 and 14 o0 the 7447,and
connect these resistors to the a, b, c, d, e, f and g segments oo the 7-segment
LED

Connect the common anode of the 7-segment LED to +5 volts

 

You will need to have the pinout for the specific LED display that you use so that you
know how to wire the outputs of the 7447 to the LEDs in the 7~segment device. ( Also,
note that the 7448 is equivalent to the 7447 except that it drives common-cathode
displays. Ground the common cathode of the LED in that case.)

V0u can see that by extending the circuit, we can easily create a complete clock. To
create the “minute hand’ section of the clock, all that you need to do is duplicate the
“second hand” portion. To create the “hour hand“ portion, you are going to want to be
creative. Probably the easiest solution is to create a clock that displays military time
Then you Will want to use an AND gate (or the R inputs or the 7490) to recognize the
binary number 24 and use the recognizer to reset the hour counters to zero.

NOTE: You can dispense with the and gate and simply wire the “2” line QB of the
hours-tens counting 7490 and the “4” line ( QC ) of the hours-ones counting 7490 and
connect BOTH to the same reset line (R1 or R2 )respectively on each of the hours 7490s.
In this manner when a 24 count occurs a reset is applied to both R1 and R2 on both hours
chips simultaneously, resulting in a reset to zero for both.

The final piece you need to create is a setting mechanism. On a breadboard, is is easy
to set the clock – just move the input wires to drive higher frequency signals into the
minute-hand section of the clock. In a real clock, you would use pushbuttons or switches
and gates to do the same thing.

If you happen to take your bedside clock or watch apart, one thing you will notice is that
there are probably not 15 TTL ICs inside. In fact, you may not be able to find a chip at all
in most modern clock or watches, all of the functions of the clock (including the alarm
and any other features) are all integrated into one low-power chip (in a watch, the chip
and display together consume only about a millionth of a watt.) That chip is probably
embedded directly into the circuit board. You might be able to see a blob of black plastic
protecting this chip. That one tiny chip contains all of the components we have discussed
here.

Scanned Original Document

scanned-original-document
scanned-original-document

Video Conversion Script for ffmpeg

Once and a while I have to convert a video made with Cheese, a .webm, or one made by my camera, .mov to an MP4 which takes up the least amount of space (as of 2017) and seems to be supported across a lot of devices.

The script is both a script to run and a reminder as to the syntax that ffmpeg expects as I seem to occasionally forget and wanted a snippet on line as a quick go to for reference.

In this one scaling is applied via the -s option and the bandwidth via the -b option is limited as well. Plus it allows you to choose the filename for the output file.

If ffmpeg -i %1 %1.mp4 is used for example it would take the input file and convert to mp4, tacking on the mp4 extension with no scaling and bandwidth limiting.

#! /bin/bash
#ffmpeg -i input.wmv -s 480x320 -b 1000k output.mp4
ffmpeg -i %1 -s 480x320 -b 1000k %2

Better Yet Do It Batchwise

For example, with a for loop, this code will simply go through the directory and convert all .webm’s to .mp4’s and it is set up to do scaling too if needed using -s hd480. It also keeps the same filename by changes the extension to the appropriate one for the output file.

#!/bin/bash

for a in ./*.webm; do
#  ffmpeg -i "$a" -qscale:a 0 "${a[@]/%webm/mp4}"
  ffmpeg -i "$a" -s hd480 -qscale:a 0 "${a[@]/%webm/mp4}"
done

 

Temperature, Humidity and Barometric Pressure Monitoring with Raspberry Pi

Brief notes on hooking up sensors for temperature, humidity and barometric sensors. These notes are kind of an outline of what I used and went through to get the sensors up an running. There are plenty of other detailed notes out there on the web, this might help fill in some blanks. Plus I figured, I took all these notes down and they might as well be published to do some more good.

Raspberry Pi Pinout

Model B IO Pins

DHT22 / AM2302

https://www.adafruit.com/products/385?&main_page=product_info&products_id=385

https://www.adafruit.com/products/393?&main_page=product_info&products_id=393

I followed this example to get the DHT22 sensor up and running all the way to executing the example code

https://learn.adafruit.com/downloads/pdf/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging.pdf

Raspberry Pi Weather Dashboard

I put all if this together to make a dashboard page for the sensors.

http://erick.mynetgear.com

 

 

morse-1 code

Cron Driven Morse Code Time Sounder

My goal was to make a new hourly chime,something with a bit of intelligence to it than just the same tone every hour. It was actually one of those random things that runs through your head when laying in bed trying to get in a mood to sleep.

A bit of history

Typically I have been using a preexisting system sound on a Linux PC to annunciate that it is the top of the hour. This helps to keep track of how long I am on the computer, time to take a break maybe. It also makes me away of the time, in case I am in the zone with coding or whatnot and need to be aware of how time flies. Once you have this, you kind of look for it, even when you are in the room doing something other than computer work.

Up to now this is what I typically had in my crontab…

00 09-23 * * * aplay /usr/share/sounds/fLight__2.0/stereo/Message.wav

I restrict the hours down, just so the thing doesn’t wake me at night if I forget to turn off the PC.

Festival

Years ago I used Festival, the text to speech program and made it annunciate the time. This works OK as long as you are at the PC. If you are away from it a bit, you don’t always pick up what the machine generated voice is saying. Morse Code has an advantage over voice, in that the tones are easy to pick up, even when faint. I have a ham license and have experienced this first hand. So that was my line of thinking with using Morse to give me the time at the top of the hour. It would be easy to not only know that it is the top of the hour but, I can tell what hour it is easily with Morse code. Plus it seemed like a fun twist. I have even thought of putting something like this on my Pi which runs 24/7 in my office. In our living room we have a bird clock, that has different bird sounds for each hour and that has been pretty useful at times, so that got me going on this whole hourly chime adventure years ago.

I was initially inclined to make my own tones but, a brief search found Stephen C. Phillips site and his Morse Code Translator. Using it I was able to create a more code “hour” sound file from 0-23, that plays the correct sounding for every hour.

It is possible to take any sound files and label them 0-23.wav and get other types of sounds to chime at the top of the hour. Birds songs, train whistles, nature sounds, the possibilities are endless.

How it works

Using the Morse Code Translator, I was able to create a series of Morse Code translations from 0-23, in WAV file format. The WAV files get put in a directory, morse-code-audio under my home folder and the following script gets called in place of the line shown above in my crontab….

#!/bin/bash

sounddir=/home/erick/morse-code-audio

# Grab the Hours off of the date.

hour=$(date +"%H")

#Call the correct file based off of the hour
 aplay $sounddir/$hour.wav

WAV Files for the Morse Code Time Sounder

I put the 0-23.wav files online, as a tar.gz.

morse-code-audio.tar

Compression, Signal Processing, Information Theory and Cryptography

Uncompressed the 24 WAV files in the tar file are a total of 348K , it is interesting just how compressible single frequency tones are. All of them compress down to a 2.8K tar.gz. I had to check twice, I thought I was missing a bunch of files. But it stands to reason when one thinks of a single frequency turned on and off slowly, has very little bandwidth. Provided the keying is shaped in a way so that it is not a pure sine wave modulated by a square wave, the pulses have to be shaped the corners rounded off to get the bandwidth below 100Hz. Thinking of Fourier transform, a tone left on from infinity has a bandwidth of zero. A digital signal, pulse shaped, on and off keying at 20WPM code is going to have a real narrow bandwidth, therefore highly compressible. The opposite extreme, white noise, would not be compressed down at all by gzip or any of the fancier types of compression. White noise is random, equally distributed across the spectrum, hence incompressible. But it makes for a hell of an encryption key for that very reason. The worlds of signal processing and cryptography do come together in interesting ways!

Resources

Stephen C Phillips has an excellent website and blog that covers a lot of technical topics among with the Morse Code Translator is an example. He also covers Python code and the Raspberry Pi for example.

http://blog.scphillips.com/

The featured image is from this site and it is an interesting read…

https://www.raspberrypi.org/learning/morse-code-virtual-radio/worksheet/

24 Hour Digital Clock Gets a Better Timebase

The last post on this clock built out of 7490 TTL decade counter chips gave a bit of back story on it and the initial troubleshooting of it’s timebase drift and noise issues that caused extraneous counts to occur. Now that the noise is figured out and solved, it is time to do something better than a plain crystal with a trimmer 7400 ( NAND Gate ) oscillator for a timebase.

Driving the clock with an OCXO

The goal was to allow the clock to be driven by an oven controlled crystal oscillator (OCXO), which would surpass the performance of the oscillator on the board. The on board oscillator can be easily pulled off it’s frequency and slaved to an external source. By using a 7414 Schmitt Trigger Hex Inverter, it is possible to take the low level sine wave output from the OCXO and convert it into a digital signal capable of entraining the on-board oscillator. By using an external master, I can pull the master OCXO off if I need it to calibrate anything else, meanwhile the clock keeps running off of it’s board oscillator. Most of the time the OCXO is not being used and can just remain with the clock.

7414-Schmitt-Trigger-on-breadboard
7414 Schmitt Trigger Hex Inverter on Breadboard

The hookup is pretty simple, I breadboarded it and found out the biasing one of the inputs of the 7414 mid range using a pair of 33K Ohm resistors in series from +5V power to ground with the input to an inverter stage on the 7414 in the middle at 2.5V, feeding in the OCXO signal, capacitively coupled  and then feeding the output of that stage into another inverter on the 7414 for a buffer, I was able to get a clean square wave at 10MHz. This I coupled to the board oscillator using a 370 Ohm resistor. The resistor is more or less a protection in case I touched it to something that I shouldn’t and I don’t want too much current to be able to flow in either direction. I also temporarily drove an LED via a 370 Ohm resistor off of the same output as a check that I was actually getting output, the LED is lit at half the brightness when it is excited by a square wave.

Initial testing with the breadboard shows that the clock now tracks time very well as compared to another clock I have that is synced to the WWV 60KHz signal.

OCXO to 7414 to TTL Clock
OCXO to 7414 to TTL Clock: Signal path is via yellow clip leads.

 

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Miscanthus giganteus

I recently saw a stand of Miscanthus giganteus at Cutler Gardens in Binghamton,NY. It is an impressive grass standing at 10-11 feet tall. I am thinking of ordering some rhizomes to grow some. It would make a nice natural privacy fence. It sure looks cool too, even when it dies off it still stands nice and tall. I imagine the snow will eventually knock it over in the winter. When I saw it, I looked it up on the little pamphlets available at the gardens and of course on Wikipedia. https://en.wikipedia.org/wiki/Miscanthus_giganteus
Who would have know that it can be actually used as a biofuel! What an interesting plant and it is a so called C4 plant as well just like corn, it can more efficiency convert water and CO2, via photosynthesis into plant material, giving it an edge in creating biomass.

I found a place to order the rhizomes too…

http://www.mapleriverfarms.com/index.php