So if you still want the delay with servo operation, then it would seem you will need to add a third 555 that generates two different pulse streams to control the servo.
Typically the pulses needed are shown below:

The pulses occur at a 20 mSec (50 Hz) interval, and vary between 1 and 2 mSec in width.
Common servos rotate over a range of 90° as the pulses vary between 1 and 2 mSec -- they should be at the center of their mechanical range when the pulse is 1.5 mSec.





pulse to position

Understood. Hopefully I can tune the timing of the DC motor to produce about a 180 degree rotation in order to avoid using the servo. Motor gets here next week so I’ll try it then. I’d like to stay away from implementing a third timer chip, so hopefully the tuning works.

 

Understood. Hopefully I can tune the timing of the DC motor to produce about a 180 degree rotation in order to avoid using the servo. Motor gets here next week so I’ll try it then. I’d like to stay away from implementing a third timer chip, so hopefully the tuning works.

I think it will still require a third chip even if you get the timing correct. The motor turns 180 then stops briefly and either reverses 180 or continues 180. This
is going to require another timer.

 

Perhaps it would be good for you to post again, exactly what you want the motor to do, and when it should do it, as that's become a little fuzzy at this point.

 

This is an overview of what this entire thread is about:
A timer circuit that does the following to output to a DC Motor:
1) Motor Starts OFF
2) Button is pushed
3) Motor stays OFF for 8 seconds
4) Motor turns on for 1 second
5) Motor OFF

I desire the motor to rotate 180 degrees. So, the 1 second is arbitrary and will require tuning. Some are saying that the motor will rotate more after the 1 second on period. Not sure until the motor ships next week and I tune the ON timing.

 

Then the motor does not need to return to the starting position until the next button press?

 

Is the motor geared to 30 RPM? If not, how do you expect it to rotate only 180° in 1 second. An ungeared motor will spin at 1000s of RPMs. In one second it will spin many times around.

And using timing to achieve an accurate amount of rotation is not going to work. It will not be accurately repeatable. Trust me. Systems that rotate a controlled amount need feedback of some form. A servo uses a potentiometer. The resistance changes as it rotates. It is also geared. To make something rotate 180°, place a physical switch and cam of some sort such that the switch is activated at the desired position.

 

Perhaps it would be good for you to post again, exactly what you want the motor to do, and when it should do it, as that's become a little fuzzy at this point.

Is the motor geared to 30 RPM? If not, how do you expect it to rotate only 180° in 1 second. An ungeared motor will spin at 1000s of RPMs. In one second it will spin many times around.

And using timing to achieve an accurate amount of rotation is not going to work. It will not be accurately repeatable. Trust me. Systems that rotate a controlled amount need feedback of some form. A servo uses a potentiometer. The resistance changes as it rotates. It is also geared. To make something rotate 180°, place a physical switch and cam of some sort such that the switch is activated at the desired position.

The motor I am looking at is geared it rotates at 200 rpm.

 

Then the motor does not need to return to the starting position until the next button press?

The motor never needs to return to its starting position. It just needs to rotate 180 degrees every button press.

 

The motor I am looking at is geared it rotates at 200 rpm.

That's about 0.15 second to turn 180.
A continuous rotating servo might work better.

 

That's about 0.15 second to turn 180.

Yeah. That’s why I want to implement a microservo rather then a dc motor. But the micro servo seems to cause bigger problems

 

How accurate do you need the 180° rotation to be?

 

How accurate do you need the 180° rotation to be?

Pretty accurate. The motor is fixed to a cam which drives a down a blade. Like a cam and follower system. It is a cutting mechanism. The motor is driving the cutting motion.

 

Pretty accurate. The motor is fixed to a cam which drives a down a blade. Like a cam and follower system. It is a cutting mechanism. The motor is driving the cutting motion.

I’d say within 10 degrees of 180. If the cam doesn’t turn near 180 then the follower will not retract back to its original position. That would be an issue because there needs to be clearance under the cutter for the next cut (or button press).

 

I’d say within 10 degrees of 180. If the cam doesn’t turn near 180 then the follower will not retract back to its original position. That would be an issue because there needs to be clearance under the cutter for the next cut (or button press).

Then I think you need either the servo motor, or limit switches to control the motor movement.

Would it be possible to use a solenoid for the cutter?

 

Then I think you need either the servo motor, or limit switches to control the motor movement.

Would it be possible to use a solenoid for the cutter?

I could use it if it is small enough. I’ve used a solenoid before with Arduino to fire a piston, but how do you expect it to drive down the razor?

 

how do you expect it to drive down the razor?

Have to see a picture of what you are trying to do before I can answer that.

 

I could use it if it is small enough. I’ve used a solenoid before with Arduino to fire a piston, but how do you expect it to drive down the razor?

This is an interesting and exciting idea. I see how solenoid valves work now that I looked it up. Please let me know what the best solenoid application would be here (e.g. solenoid valve, etc.). I will mention that the razor must travel 1 inch in length for a full and proper cut.

 

Have to see a picture of what you are trying to do before I can answer that.

The Cam is the blueish thing right above the razor. This is an example using a servo and bevel gear train.

 

What is the stroke length for the razor?

 

What is the stroke length for the razor?

If by stroke length you mean the length the razor cuts to its ending position (before retracting back up), then it is 1 inch.