stepper motor drive circuit (clock )

[radhi]

I need a circuit to drive a bipolar stepper motor used in quartz clocks operated either 1.5V or 3V.

Instead of 1Hz frequency generated by a circuit from fixed crystal frequency in all the quartz clocks, i have a to and fro moving pendulum (with 2 secs beat)which generates an output pulse of 300mv every instant whenever permanent magnet fixed beneath the moving pendulum passes over a fixed coil.
The pendulum is also driven by the same coil.
A simple electronic circuit is built in to drive coil-1 which imparts pendulum to move to and fro and the other coil-2 generates 300 mV due to magnetic flux.
I would like to drive the bi-polar stepper motor only (already provided in the quartz clock) with a suitable circuit with only the input i.e. 300mV pulse.
The required circuit shall generate the following:
a) output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak.
b) second output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak - AFTER 1 sec.
c) The circuit shall able to run by 5V to 6V source.Preferably by a battery and shall consume very less power.
if you need any info. i would feed instantly. Regards.

 

[ljcox]

Is the 300 mV from coil 2 positive going and then negative when the pendulum swings from say left to right and then Neg/pos when it swings the other way?

In other words, does the signal go through zero on each swing and is it the same slope for each swing, or does the slope alternate?

What I have in mind is a zero crossing detector (or 2 ZCDs) followed by a monostable to provide the pulse and then possibly a Flip Flop to provide the pulse after 1 sec.

It would help if you can post a drawing of the 300 mV signal, ie. its wave shape.

 

[Roff]

The required circuit shall generate the following:
a) output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak.
b) second output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak - AFTER 1 sec.

Am I missing something? These seem to be identical waveforms with no phase offset.

 

[radhi]

Is the 300 mV from coil 2 positive going and then negative when the pendulum swings from say left to right and then Neg/pos when it swings the other way?

In other words, does the signal go through zero on each swing and is it the same slope for each swing, or does the slope alternate?

What I have in mind is a zero crossing detector (or 2 ZCDs) followed by a monostable to provide the pulse and then possibly a Flip Flop to provide the pulse after 1 sec.

It would help if you can post a drawing of the 300 mV signal, ie. its wave shape.

All details are given in drawing. could you comment.

 

[ljcox]

I'll think about it and post a suggestion later today or tomorrow

 

[ljcox]

The 300 ~ 500 mV pulses are rather small. They would need to be amplified. Does anyone know of a low current amp?

Or a low current Schmitt Trigger that can be set/reset by the pulses. Another possibility is a low current bistable (Flip Flop) that can be set/reset by the pulses. Any suggestions?

Alternatively, can you take the pulse from the junction of L1 and C1?

If so, what amplitude is it? Is there any ringing? Obviously it will be centred around +3 Volt, but that will not matter if the amplitude is adequate. The issue with taking the pulse from the right hand side of C1 is that it is clamped by the transistor BE junction.

 

[radhi]

The 300 ~ 500 mV pulses are rather small. They would need to be amplified. Does anyone know of a low current amp?

- Will LM 311 would do the anplification job.

 

[ljcox]

- Will LM 311 would do the anplification job.

The LM311 is a voltage comparitor, not an amplifier. However, it could be configured to work as a Schmitt Trigger to do what we want. But is has a supply current of about 3 mA and needs +5 Volt & - 5 Volt supplies.

Is this suitable for your application? I would assume not since you want it to be battery operated.

You did not answer my other questions.

Another question, can you insert a resistor between L1 and C1?

 

[radhi]

[

- The 300 ~ 500 mV pulses are rather small. They would need to be amplified. Does anyone know of a low current amp?

-
- Or a low current Schmitt Trigger that can be set/reset by the pulses. Another possibility is a low current bistable (Flip Flop) that can be set/reset by the pulses. Any suggestions?
-
quote="ljcox"]

- Will LM 311 would do the anplification job.

1. The LM311 is a voltage comparitor, not an amplifier. However, it could be configured to work as a Schmitt Trigger to do what we want. But is has a supply current of about 3 mA and needs +5 Volt & - 5 Volt supplies.

2. Is this suitable for your application? I would assume not since you want it to be battery operated.
-- i would prefer to run with battery source. if envitable, i do not mind to go for a +5V/=5 V supplies required for most of the ICs.

You did not answer my other questions:
a) Alternatively, can you take the pulse from the junction of L1 and C1?

- If so, what amplitude is it? Is there any ringing? Obviously it will be centred around +3 Volt, but that will not matter if the amplitude is adequate. The issue with taking the pulse from the right hand side of C1 is that it is clamped by the transistor BE junction.
r questions.:
-i have not measured it. I would answer to you soon.

b) Another question, can you insert a resistor between L1 and C1?
yes. What way it helps.

 

[ljcox]

A simple electronic circuit is built in to drive coil-1 which imparts pendulum to move to and fro and the other coil-2 generates 300 mV due to magnetic flux.

You appear to have transposed the coil numbers. In your circuit, you have shown L2 as the driving coil. But in the quote above it is Coil-1.

If the pulse at the junction of L1 and C1 is large enough, the amplifier won't be necessary. If not, then the insertion of a resistor may provide enough amplitude.

 

[radhi]

[You appear to have transposed the coil numbers. In your circuit, you have shown L2 as the driving coil. But in the quote above it is Coil-1.

- Yes i agree with your observation. L1 coil is the sense coil and L2 coil is the drive coil.

If the pulse at the junction of L1 and C1 is large enough, the amplifier won't be necessary. If not, then the insertion of a resistor may provide enough amplitude.
- I agree. could you provide me with a circuit to drive the stepper motor.

 

[ljcox]

Here is a suggestion. I don't know if it will work because I don't know the amplitude of the pulse from L1.

If the voltage generated by the coil is too small, then Q1 will not turn on due to the voltage dropped across D1.

If so, then another transistor will be required.

R6 is to limit the current through the motor to the required level.

R3 may be necessary, depending upon the resistnce of L1.

Q1 turns on when x goes positive and Q2 turns on when y goes positive. The pulse from Q2 is stretched by C3 R5 and should be about 200 ms with the values given; but given the wide spread of the CMOS Schmitt Trigger thresholds, you may need to vary R5 to suit.

 

[radhi]

[R6 is to limit the current through the motor to the required level.
- what should be the approx. value of R6?

R3 may be necessary, depending upon the resistnce of L1.
- what should be the approx. value of R3 ?

Will the output waveform would be like given below in attachment.

Thanks for the ckt. i'll build the ckt and will give the feedback.

To openly say, i am novice in electronics but i read a lot to understand.

i agree that the ckt you have given is purely to meet my requirement (battery source <6V), but if you choose other means using NAND schmitt trigger with JK flip flops or D-flip flop NAND with schmitt trigger will the power drawn will be more?

 

[ljcox]

[R6 is to limit the current through the motor to the required level.
- what should be the approx. value of R6? I don't know, it depends on the current drawn by the stepper motor. Only you can answer this question.

R3 may be necessary, depending upon the resistance of L1.
- what should be the approx. value of R3 ? I don't know, it depends on the resistance of L1 and the voltage generated by L1. Only you can answer this question.

Will the output waveform would be like given below in attachment. No, see my attachment

Thanks for the ckt. i'll build the ckt and will give the feedback.

To openly say, i am novice in electronics but i read a lot to understand.

i agree that the ckt you have given is purely to meet my requirement (battery source <6V), but if you choose other means using NAND schmitt trigger with JK flip flops or D-flip flop NAND with schmitt trigger will the power drawn will be more? No, CMOS draws very little current.

The waveforms below are my understanding of what you asked for.

 

[radhi]

Thanks for all the answers.
Will the output waveform would be like given below in attachment. No, see my attachment

-- i read about clock circuit operation some where in the net (see attacment) which is like stepper motor. accordingly, i had mentioned in my first quote as follows:
"The quartz clock The required circuit shall generate the following:
a) output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak.
b) second output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak - AFTER 1 sec."

- i should have explicitly spelt out my output needs in wave form intially which i mentioned in my last quote only. This anamoly created to you to think the output wave form as mentioned in your last quote.
- Could you kindly make some changes in the ckt to get the output wave forms as mentioned in my last quote

 

[ljcox]

quote
The required circuit shall generate the following:
a) output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak.
b) second output of 1 Hz with 20 to 30 % duty cycle with positive 1.5V or 2 V peak - AFTER 1 sec."
This does not make sense. The attachment below shows, a 1 Hz signal delayed by 1 second is also a 1 Hz signal.

What I need is a timing diagram of what you need.

Your attachment did not help me at all.

 

[radhi]

timing diagram

quote
[

What I need is a timing diagram of what you need

please see attachment the timing diagram .

 

[ljcox]

Your output 1 and output 2 have 2 second periods and are therefore 0.5 Hz, not 1 Hz.

And they are very similar to the diagram I posted on Dec 26.

The duty cycle can be adjusted to whatever you need.

However, I am dubious about the output from L1. I expect it will give a positive and negative pulse each time the pendulum passes it, not positive pulse on one pass and a negative on the other. Are you sure that your L1 waveform is correct?