Editing PIC based Stepper Motor Dancing Analog Clock

*Status: This is a draft. Code works but still in refinement, code available, email russ_hensel Also still refining the project.

This is an analog clock, with real hands driven by stepper motors.  A clock for the confused dyslexics amoung us, for more informatinon on Dyslexia see DAM ( Mothers Against  Dyslexia ). Because stepper motors are quite powerful the clock could be made quite large, 3 feet in diameter is probably within reach still using inexpensive ( salvage ) stepper motors.  The project description includes eagle files for the circuits and a BoostC project with source code for the PIC.

 

 

 

 

*Low side Driver Chip -- but any transistors with reasonable beta and enough current handling capacity could be substuited.

|Hour and minute hands may "dance" at special times, see the video at: [http://www.youtube.com/watch?v=Dajo2r___P8 Short Video of Clock]

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|Dual Stepper motors

|Salvage from printers and floppy drives.  Independent drive of each hand.

This is a straight forward half wave rectifier with a linear regulator.  It is powered by a wall wart transformer rated at about 9 volts.  The unregulated voltage is over 9 volts ( 9 * ( 2 ^ 1/2 )) by simple theory.  This unregulated voltage is used directly by the steppers so choose you wall wart to match your stepper motors.  You should also size the filter caps based on the current that will be used by the motors.  A couple of volts of ripple is not a problem as long as you have enough overhead for the 5 volt regulator ( the PIC might run on less, let me know if you try it ).  An important part of the power supply is a 60 hz, roughly square wave.  It is clipped off from the AC input.  The 60 Hz power line tends to be very accurate over the long term, less so if you suffer power outages.  You could run the clock on batteries but the motors load down a battery pretty badly and you would need a different timing signal ( the original code has a subroutine for timing off the crystal ).

|You need one with AC output to get the 60 Hz timing signal from the power line.  Mine is a 9 v 800 ma unit.  I found it somewhere.  The unregulated rectified voltage should be good for your motor, so check your motor against the wall wart.  The 9 volt unit does a good job of driving a 12 volt motor.  Motors do not need very well regulated power.

|Clip the AC for the time keeping to +5 and 0 volts.  Protects the input of the PIC.  I just used standard small signal diodes.

|Mounting holes.  No electrical connection.

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Single sided, for toner transfer, in Eagle ( semi-final, less ground plane, files may be more up to date ) To get a readable copy download the Eagle files and open in Eagle, see: [[Techniques#Software_design_tools | Techniques, Software Design Tools]]

|You need one with AC output to get the 60 Hz timing signal from the power line.  Mine is a 9 v 800 ma unit.  I found it somewhere.  The output voltage, when rectified, needs to be enough to drive the motor, the PIC runs off a regulator so it does not care much about the input voltage.

|My favorate 16 series part, relatively lots of memory and pins.  Bigger than you need, but only about 8 bucks.  Try with an 18 series part, should not be hard and will leave you more up to date.  Let me know.

|( or could be 2 momentary push buttons ) one moves the hands up, the other down, in the set and adjust modes.  From my junk box.

|10k more or less

|CQ1, CQ2 = capicators for the crystal

|about 20 pf seems to work, see the PIC16F877A manual

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|4 meg Hz is what I used.  May be quite a bit faster than needed, I have not looked into this.  The 4 meg crystal seems to work ok on a proto board.  Note that some of the code is dependent on this frequency, but could be fairly easily changed.

|10K more or less

|RB1 ... RB6 = Pull up resistors

|10K more or less

|RRA2, RRA3 = Pull up resistors

|10K more or less

|RRA1 = Pull Up resistor

|10K more or less

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|DRIVER  = Driver

|Driver chip for stepper.  ULN2803. Good for up to .5 amp 35 volts I think.  Could use discrete transistors ( possibly darlingtons ) if you want higher current.  You should not need more current unless you make a really big clock.

|RMC  = Pull up resistor for master clear ( pull down with push button switch to reset ).

|10k more or less

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|VDD = Positive Power

|5 volts from power supply.

|G1  = Ground Connection

|To the power supply.

|SW_UP, SW_DOWN = Setting switch

|I used a momentary double throw, single pole, you could use 2 momentary push buttons.

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The stepper control is half step.  The activation of the coils is determined by an array which hold the 8 different activations of the coils.  My stepper motor has 200 full steps ( 400 half steps ) per revolution.  You should be able to adjust the code for different steppers.  Much of the steppeer code is very similiar to that in [[Stepper Motor Tester]] which may or may not have a better explanation of the code which drives the stepper motor.

The zip file contains the entire source bootst project.  Unzip into a directory and open in source boost.  There are some additional notes at the top of the main source file.  Follow the instructions there, they will tell you about any compiler and/or linker options, and report on memory usage from a recent compile of mine.  The compile should run without error. 

 

 

 

 

 

==== Without the Serial Interface ====

*Before plugging it in set the hands to 12 oclock and and 0 minutes ( if the hands are accessable, else skip this ).

*The clock will be set to 12:00 and will immediately start running.  But the hands may not be initialized or adjusted to the correct zero positions.  To adjust them change the mode switch to Adj Hour Hand  and manipulate the up down switch untill the hour hand moves to 12:00 ( this does not change the internal time of the clock ), switch to Adj Minute Hand and adjust it to 0 minutes.

*Switch the clock back to run, the hands may move a bit, the time is very near 12:00 ( unless it took you a long time to adjust the hands ).

*Switch to set hour to set the correct hour.

 

 

 

 

 

 

 

Then send an ! to the clock, the clock should respond with "Stopped; turn on serial mode" and you can then use the commands in the following table.

 

 

|Stop whatever is running, enter serial control mode.

|Adjust the hands to their 0 positions ( 12:00 ). If they are not correctly line up use the J and Y commands below

|( Y is above the H ) adjust the hour hand by an amount n, where n is a signed number from about -100 to 100.