On 1/19/14 10:11 AM, Chuck Harris wrote:
Given the relatively low currents needed by the clock
motor, and the relatively high currents that can be
sourced/sinked by the arduino, and the fact that the
motor winding is floating relative to the arduino,
one could probably connect the motor like this:
D0---SomeResistor--MOTOR-----D1
Then, how to describe the way to drive it?
Well, starting out with D0=D1=0,
Set D1=1, then in 0.1 sec set D0=1.
Wait 0.9 sec then:
Set D0=0, then in 0.1 sec set D1=0...
Wait 0.9 sec then:
wash rinse repeat...
That's what I'm going to try.
Actually, on an arduino, you can set the output pin to Hi Z..
So it's more like
#define PulseLength1 100 // milliseconds
#define PulseLength2 100
void ClockTick(){
digitalWrite(D0,LOW); //preload the bits
digitalWrite(D1,HIGH);
pinMode(D0,OUTPUT); // now make them an output
pinMode(D1,OUTPUT);
delay(PulseLength1); // wait til pulse first part
digitalWrite(D0,HIGH); // flip direction
digitalWrite(D1,LOW);
delay(PulseLength2); // wait til second part
pinMode(D0,INPUT); // turn off pulse
pinMode(D1,INPUT);
}
That way you're not drawing power most of the time..
-Chuck Harris
Jim Lux wrote:
On 1/19/14 9:17 AM, Chuck Harris wrote:
The usual quartz clock that runs off of a AA cell is a little
trickier to drive than you might think. You need to feed
its stepper motor coil with an alternating +1.5V and -1.5V pulse.
The pulse follows the rising or trailing edge of a 1/2 Hz square
wave. I have driven them using a series capacitor and resistor
to ground...arranged as a differentiator, but I don't recall the
part values anymore.
You arduino could certainly be made to generate such a pulse using
a couple of resistors and a couple of digital outputs in a simple
DAC sort of circuit.
Yeah.. that *is* the challenge.
Use two outputs and make a sort of "H bridge"
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