Wednesday, November 8, 2017

Rumination of Uselessness

Let us return to the Useless Machine topic one more time.

Classical useless machine usually made out of four electrical components, namely:
  • Electrical battery.
  • Gear motor.
  • DPDT switch (usually toggle, sometimes rocker).
  • Micro-switch.
This is probably minimal set: it is hard to imagine anything more efficient. But once an idea came to my mind: maybe such a machine  is not absolutely perfect. Useless machine must cut itself out of power as soon as it returns to the original state. That achieved with help of the micro-switch.  Machine arm,while returning back, pushes switch, its normally closed contact becomes open,  machine fully stops and looks dead. But if tester tries to move an arm manually, micro-switch is released again, its closing contact provides power to the motor. That case is visible on the clip of Rocker Switch Useless Machine starting at second 19. So machine here actually is not dead, it just plays dead! That's  good opportunity for the new design : make the machine, which will allow manual rotation of the arm, when machine is turned off. In other words make the machine really dead at the end of its working cycle. To achieve that I decided to get rid of micro-switch and  use an energy stored in the capacitor, charged while machine arm moves forward, for backward movement. Below you can see circuit diagram of such a machine:
When switch connects motor to the battery and motor moves the arm forward, electrical current is flowing through  the circuit of diode and relay, mounted in parallel to the motor. Relay  is forced to close its normally opened contact. Through that contact (and small resistor) capacitor is connected to battery and receives some charge. 

When arm turns the switch back, motor is disconnected from battery, but connected to the capacitor in the opposite polarity. Motor rotates backward and returns arm to its original state.  Diode now stays in the opposite direction on the way of electrical current,  so relay contact stays open and capacitor is disconnected from the battery. Capacitor mostly is discharged providing the movement of the motor, the rest  will be discharged through the stopped motor winding. You see, in theory it looks simple. But I must tell you that this design is much more demanding on the spec of components, compare to classical schematic. After some trial and error iteration I came up to the next set component:
  • Solarobotics gear-motor GM17  ( I could not make it working reliably with GM2 or other motors with similar spec).    
  • Super capacitor 0.1 F. (I used NEC 5.5 V capacitor). Bigger capacitor would be fine but smaller probably not.
  • 5V relay. Here type is not that important. 
  • Schottky diode. Here type is not that important. 
  • Resistor 5 Ohm. It is optional but it keeps electrical current trough the battery under 1 Amp at the beginning, when the capacitor is fully discharged. Type does not matter here, but better to have 0.5 W.
  • Four 1.2 V rechargeable batteries. Type does not matter. 
As you can see on the video tester may manually  rotate the arm when machine is turned off.  Done!
I published more detailed description on instrcuctables site

Update 11/12/2017. fixed bug in diagrams: missing wire between switch terminals.

Saturday, December 31, 2016

In the Moonlight

This is the moon simulator with bat silhouette which I made as a decor for this  Halloween.

The core part of the project is twelve backlight white LED modules ( I bought them from the adafruit). LEDs are controlled by Atmega328 micro controller. The schematic of the project is fairly simple:

Adm here you can see project assembly with some internals visible:

Twelve LED modules put in the middle of sandwich made out of two Plexiglas  sheets attached with the help of Velcro strips.  Paper Bat attached to the front of the moon with Velcro as well as front and back cardboard shields .

 Program to control the device is short enough to be present entirely in this blog:

 * moon.c
 * Created: 10/22/2016 1:14:19 PM
 *  Author: jumbleview
#include <avr/io.h>
#include <avr/interrupt.h>
#include "./pt-1.4/pt.h" //

typedef enum {OUT_LOW, OUT_HIGH} OutputLevel;
volatile uint16_t pulses;

#define pinOut(port, bit, outLevel) \
(DDR##port |= (1 << ( DD##port##bit)));\
switch(outLevel) \
 case OUT_LOW: (PORT##port &= ~(1 << (PORT##port##bit))); break;\
 case OUT_HIGH: (PORT##port |= (1 << (PORT##port##bit))); break;\
void clearAll()
{ // set all outputs low
 DDRB = 0xFF; PORTB = 0;
 DDRC = 0xFF; PORTC = 0;
 DDRD = 0xFF; PORTD = 0;
void activateTimer0()
 pulses = 0;
 TCCR0A=0; // Normal operation
 TCCR0B=2; // f divider 64  : about 2 ms for interrupt ...
 TIMSK0 = 1; // for system clock f= 1Mhz (CKDIV8 set)
struct pt wpt; // protothread descriptor

int moonlight(struct pt* mlpt)
 PT_BEGIN(mlpt);  // New Moon 
   pinOut(C,5,OUT_HIGH); pinOut(B,1,OUT_HIGH);
   pinOut(D,0,OUT_HIGH); pinOut(B,2,OUT_HIGH);
   pinOut(D,1,OUT_HIGH); pinOut(B,0,OUT_HIGH);
  PT_YIELD(mlpt); // First Quarter   
   pinOut(D,2,OUT_HIGH); pinOut(D,7,OUT_HIGH);
   pinOut(D,3,OUT_HIGH); pinOut(D,6,OUT_HIGH);
   pinOut(D,4,OUT_HIGH); pinOut(D,5,OUT_HIGH);
   pinOut(C,0,OUT_HIGH); pinOut(C,1,OUT_HIGH);
  PT_YIELD(mlpt);  // Full Moon + Red Eyes
   pinOut(C,0,OUT_LOW); pinOut(C,1,OUT_LOW);
   pinOut(C,5,OUT_LOW); pinOut(B,1,OUT_LOW);
   pinOut(D,0,OUT_LOW); pinOut(B,2,OUT_LOW);
   pinOut(D,1,OUT_LOW); pinOut(B,0,OUT_LOW);
  PT_YIELD(mlpt);  // Third Quarter
   pinOut(D,2,OUT_LOW); pinOut(D,7,OUT_LOW);
   pinOut(D,3,OUT_LOW); pinOut(D,6,OUT_LOW);
   pinOut(D,4,OUT_LOW); pinOut(D,5,OUT_LOW);
  PT_RESTART(mlpt); // New Moon
 uint16_t mod =pulses%750;
 if (mod == 0){
int main(void)
 PT_INIT(&wpt); // initiate protothread structure...
    while(1) { }

To  compile and load program into the controller memory I used Atmel Studio 6.1. Code includes three header files.

  • File "io.h" contains definitions to work with input/output (comes with Studio installation)
  • File "interrupt.h" is defining interrupt vectors (comes with Studio installation)
  • File "pt.h" is Adam Dunkels implementation of protothread library.
Protothred library deserves some additional notes. I included it to my programming  tool box recently and nowadays use it any time I need to program embedded devices in "C ". It provides multitasking framework and allows to code device states efficiently and conveniently.  I highly recommend to try it for any programmer  who works with micro-controllers in "C".

As you can see device is simple to made and program. Some additional details you can find in my "Instructables" project.

The only problem I see is relatively high project price. Mostly it is the price of LED modules ($2.50 for each). Nothing could be done here. To gain some additional benefits I decided to substitute  Bat with Reindeer so the device is quite usable  as winter decor:

Saturday, September 3, 2016

Windows Console on Demand in Go

There are two kinds of Windows programs: Windows GUI or Console Application. There could be third case:  process, which does not have any visual representation at all and needs to be running in the background. For that case program maybe be built as Windows GUI, but it should not have any code, which creates Windows objects.  But what if  you want from application sometimes  to be silent and sometimes  to be verbose and to have a console. Possible use cases are:
  • Printing version of the utility if started with special flag (like -V)
  • Program needs complicated tune up through the  command line arguments or configuration file, but normally is  running on the background. It would be beneficially to have a choice either run it with console or run it quietly.
That could be achieved by compiling application as Windows GUI and allocating  or attaching console to the process during run-time if needed. There are a lot of examples how to do that in C/C++. When I myself looked for the solution several years ago I have found this link  helpful. Fragment of the code, which creates console may look like this.

 // taken from:

 int fdout = _open_osfhandle((long)GetStdHandle(STD_OUTPUT_HANDLE), _O_TEXT);
 FILE* fout = _fdopen(fdout, "w");
 *stdout = *fout;

 int fdin = _open_osfhandle((long)GetStdHandle(STD_INPUT_HANDLE), _O_TEXT);
 FILE* fin = _fdopen(fdin, "r");
 *stdin = *fin;

Nowadays I found myself  programming more and more in Go. While initially Go compiler was intended for Linux only,  that is not the case anymore. Windows now is the first class citizen in the Go word. Recently I needed to create application, which may open the console if that demanded by  command line argument, but work invisibly  otherwise . To my surprise there were not that many online information how to do that in Go. I did find one answered question in StackOverflow. Alas, proposed solution did not work for me out of the box. But using it as starting point and after some googling I have found workable solution. Here is sample of Go application, which will allocate console, print some prompt, wait for keyboard input and quit.

// go build -ldflags -H=windowsgui
package main

import "fmt"
import "os"
import "syscall"

func main() {
 modkernel32 := syscall.NewLazyDLL("kernel32.dll")
 procAllocConsole := modkernel32.NewProc("AllocConsole")
 r0, r1, err0 := syscall.Syscall(procAllocConsole.Addr(), 0, 0, 0, 0)
 if r0 == 0 { // Allocation failed, probably process already has a console
  fmt.Printf("Could not allocate console: %s. Check build flags..", err0)
 hout, err1 := syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE)
 hin, err2 := syscall.GetStdHandle(syscall.STD_INPUT_HANDLE)
 if err1 != nil || err2 != nil { // nowhere to print the error
 os.Stdout = os.NewFile(uintptr(hout), "/dev/stdout")
 os.Stdin = os.NewFile(uintptr(hin), "/dev/stdin")
 fmt.Printf("Hello!\nResult of console allocation: ")
 fmt.Printf("r0=%d,r1=%d,err=%s\nFor Goodbye press Enter..", r0, r1, err0)
 var s string
I would like to point some details about syscall.Syscall invocation for AllocConsole :
  • This function  has five arguments. It is different of what you will find in the online Go Doc . Looks like doc references Linux definition, which is not the same as Windows.
  • Second parameter here is number of arguments in dll function. For our case it is 0.
  • Function returns three variables, but only first is really meaningful. It is the result returned by AllocConsole function. Second variables always 0. Third variables  is an  error, but in cannot be analyzed in the regular Go way as far as it is never nil.  Still it could be useful: in case of success its value is different from value on failure (for example if application was build with no windowsgui flag and already has the console ) .

Saturday, April 9, 2016

Not for Insulation Only

Hobbyist and DYI makers very often extend usage of elements and components beyond its usual assignments.  I would like to share with you one such a case. 
Whenever you drill through the wooden or plastic sheet you has to be really careful not to drill through. The common well know method to prevent that is to use tape or scotch wrapped around the drill bit. Once I was out of tape and had to look for substitution. Piece of  heat shrink tube came in handy. It fitted drill bit exactly, I just needed to cut proper length of it. That was very lucky finding. I entirely stopped using tape for this task and switched to heat shrink or straw tubing. Especially convenient it becomes  for projects which  needed drilling with the same drill size but with different depth. Switching between tubes can be done in a second.  
The best result is achieved when tube sits tight  on the drill bit. In case you does not have exact heat shrink size, you may cut tube, which is too narrow,  alone. It will still work.  But you need to be more careful to stop drilling right at the moment when tube touches the surface. Otherwise it may be torn away by drill rotation.

Heat shrink actually suited for various tasks. I even   published blog, picturing some of  them :,  Here is list from that blog in a short:
  • Controlling depth of drilling (that idea you actually see here).
  • Using heat shrink while hanging picture  on sheet rock wall
  • Protecting awl tip
  • Keeping tweezers tips together. 
  • Making paper clip to work better. 

That topic got some attention and was even featured by one of the site editor.  Author Phil B told me about one more usage of heat shrink:  fixing claps on kindle reader case. I am sure there are many more cases which extends usage of heat shrink tubes.

Updated: 11/28/2017. Today I read about one more very useful usage of heat shrink: as thread locker.
Author Left-filed Designs published this blog . Very good. Will use myself for sure.

Sunday, January 11, 2015

Computer Desk Hutch with Sit or Stand Option

This project is a remake of the DIY project "Sit-n-Stand monitor station" described in the my old post: How did I join the Uprising. Recently my family moved into the new house and a lot of old stuff including some of DIY things did not survive the moving. I have to make the  station again. This time it  looks less DIY and more furniture like  (I hope). The basic principle is the same: desk with monitor moves up and down within sides sliders. Pulley system with counter weight compensates gravity force making moving easy. But there are some  differences:
  • Instead of single pulley line in the middle of the desk there are two lines on both sides of the desk.
  • I made desk as light as possible (but without any sacrifice of sturdiness).  
  • Light desk allowed me to switch from 3-times advantage pulley system to 2-times advantage system. As a result of that counterweight moves withing the boundaries of the hutch.
  •  I mounted  two shelves in the inner side of the hutch making some use of hutch volume.
Detailed steps of this project is published on the "Instructables" site right here: Sit&Stand Computer Desk Hutch . I even submitted it to couple of "Instructables" contests.  I cannot tell that submission made the big splash but project got some attention. While it does not win first prize it reached one contest final and here is my award: "Instrcutables" robot t-shirt. 

Saturday, November 1, 2014

Business Card Holder with $805 Price Tag

No, I did not pay that many for this cardholder. I am not even sure I ever will pay $5 for any  cardholder. I got mine completely free. It was taken  out of computer, which was prepared to be utilized by E-waste service. Processor passive cooler  grabbed my attention and pretty soon I have found some use in it. That was an easiest project I ever made. Out of curiosity I did the online search to find out the pedigree of this beast.   And here you can see the result.

Indeed it has a spectacular specification and outstanding price. That money may buy you Apple MakBook Air nowadays. Why people complain about an inflation?

Friday, July 4, 2014

Useless Machines, Atmel Controllers & Protothreads

This is the project I made in 2010 as a response to the publication about useless machines in Make Magazine1. In overall excellent article there was one statement which looked controversial to me. Author stated that a machine with a microprocessor does not cut itself completely off power and from that point of view cannot be fully qualified as useless machine. This is not true. Sure you can build a machine with microprocessor which at the end of cycle cuts itself off power. And here is its wiring diagram of the machine from the clip above.

As central component this project utilizes Pololu B-168 controller 2 with Atmel ATmega168 as a brain. In addition controller has two H-bridges for bi-polar load. One bridge in this project controls the motor, another controls the reed relay which keep the machine on power disregarding of the control switch state. To eliminate toggle switch (the reason for that you can read here) I designed the push button custom made out of two micro-switches. To justify presence of the controller more complicated task assigned to the machine. This task could be described in in these statements:
  • The Machine waits till tester hits the button. With first hit turn itself on.
  • Thew Machine waits some time if there is no hits anymore.
  • The Machine calculates the number of hits.
  • If pause after last hit is big enough working cycle begins and the machine arm hits button as many time as tester did.
  • At the end machine cuts itself off power.
While preparing this post I decided to rewrite program having in mind to try one well known but new to me technique, namely Protothreads 3. This is the framework based on C language trick which allows operator switch to be embedded inside C code blocks like if, while or for. Such obscure language feature allows to use case statements as breakpoints where the task may yield execution to other tasks and from where it can resume execution when it gets the control next time. For the detail explanation I would reference you to author website. After reading it you will understand why not everyone in programming community accepts these ideas and why there is no known company which includes it into the corporate coding standards. But for hobby project I can use whatever I like, right? Fragment of the code below contains protothread routine which implements machine working cycle 4.

// script routine
int protothread(struct pt* upt)
{  // called each timer interrupt 
 static int count=0, ix;
 static u_time timer;
 PT_BEGIN(upt); // PT_INIT is called form the main function
 // just in case to avoid race condition at the end
 turnRelay(DeviceON); // keep device powered 
 do { // counting cycle
  timer = schedule(750);
 } while(!isExpired(timer));
 for(ix = 0; ix != count; ++ix) { // working cycle
  timer = schedule(20);
  timer = schedule(20);
 turnRelay(DeviceOFF); // kill the machine
 timer = schedule( 20);
 return PT_EXITED;

See for yourself but to me it looks like good pseudo code which expresses program logic in clear and conscious way.
And at the end some observations from my limited experience with protothreads:
  • All yields/resumings of particular protothread have to be in the same protothread routine, in other words you cannot spread switch case statements across more then one function.
  • Protothread states must not be stored inside local auto variables, only static or global variables have to be used.
  • When working with Microsoft Visual Studio projects you must change default project setting of Debug Information Format field from Program Database For Edit and Continue (/ZI),to Program Database(/Zi). Otherwise your program will not compile.

1 Brett Coulthard. '"The most useless machine" (Issue 23 of Make Magazine). 2010
2 You cannot buy it anymore but there is the substitution with a better functionality in the same package but with slightly different wiring.
3Protothread Home Page.
4 The whole source code is available at this storage.