It doesn't do anything bad, but using a NPN instead of a PNP forces you to set it up in follower mode which becomes reliant on the divider created by the 4017 and the LED net, as I stated above.

 

Your Q1 will start to turn off as the trigger voltage approaches 2/3 V, but that is not a big deal. The main reason was to make it work with the yellow LED. Now that I think about it though, what is the point of the 4017? You could just double the size of C1 and feed the output of the first 555 to Q1.

It doesn't do anything bad, but using a NPN instead of a PNP forces you to set it up in follower mode which becomes reliant on the divider created by the 4017 and the LED net, as I stated above.

ooh I see. I didnt get that was what you meant. Thanks. It makes sense.
As described I want the circuit to terminate after the servo has moved 5 times. And that is why I use the 4017.

 

I don't think that the output of a 555 can drive your servo. Try using a transistor as a driver (being driven by the 555).

But the 555 does drive the servo when LED2 is not in the circuit.

 

But the 555 does drive the servo when LED2 is not in the circuit.

I explained this before. Your LED is drawing so much current that there isn’t enough left from the 4017 to drive the transistor. It looks like a dead short to the transistor base.

Increase the 330Ω ohm resistor significantly (someone mentioned 10kΩ), or add another transistor to drive the LED with a lower current or (I’m not sure you can do this in your circuit) move the LED after the transistor.

BTW, you stated the LED needs 20mA. That’s likely the maximum allowed current. Modern LEDs may turn on with as little as 2mA. That knowledge should make you feel better about increasing the LED current limiting resistor. And may adequately reduce the current demanded from the 4017 when your LED is in the circuit.

If you don’t understand this, please ask more questions. Please don’t ignore it, because that will make you getting an answer more difficult and drawn out.

 

Actually with the transistor in follower mode its input impedance is very high, so its being starved of voltage not current.

But, I'm just being picky.

 

As described I want the circuit to terminate after the servo has moved 5 times. And that is why I use the 4017.

OK, that's a good reason! I missed that part.

 

I explained this before. Your LED is drawing so much current that there isn’t enough left from the 4017 to drive the transistor. It looks like a dead short to the transistor base.

Increase the 330Ω ohm resistor significantly (someone mentioned 10kΩ), or add another transistor to drive the LED with a lower current or (I’m not sure you can do this in your circuit) move the LED after the transistor.

BTW, you stated the LED needs 20mA. That’s likely the maximum allowed current. Modern LEDs may turn on with as little as 2mA. That knowledge should make you feel better about increasing the LED current limiting resistor. And may adequately reduce the current demanded from the 4017 when your LED is in the circuit.

If you don’t understand this, please ask more questions. Please don’t ignore it, because that will make you getting an answer more difficult and drawn out.

Yes you did and I did understand it the first time Maybe you misread something. (You are quoting yourself).

I will look into it this weekend. Thanks again.

 

I have read and tried multiple suggestions but none of them gave me a better result than the one dl324 drew for me.

What I understand is that the IC's works individually and together as long as yellow diode is pulled out.

It has not been possible for me to make the servo toggle between two positions and make the yellow led light up all at once. Even not with dl324's suggestion for a replacement of the Q1.
The yellow LED will be removed in the end though. As I said it is only for me to see what is happening in the progress of creating the circuit.

I am afraid that this is what I can contract from this and simply have to give up. Even though I made the IC's work individually it seems I dont understand to do the calculations (dont even know what calculations) and the connections between them to put it all together and work as one circuit.

Would it be too time expensive for one of you to draw a circuit with same components (2 x 555 and 4017 at 6V this time) like you would have created it for me to put together on a breadboard? I have no idea. If it isn't, I would still learn, see and understand what I was supposed to have done. I think I have come a long way with what I have accomplished so far.

The circuit is to be used in a Santa Jumping Jack. The servo motor are to simulate 5 pulls in the string to make Santa jump/move. The circuit are going to be powered by 2 x 3 volts button batteries (6V).

 

Why not just put the LED on one or more of the other 4017 outputs to check its function? (maybe the carry out) Don't forget the resistor.

In your original description you seem to imply that you wanted a speed change on the servo between 4017 output pulses, also the schematic seems to indicate this, but when I watch the video it seems to only stop and go?

If you don’t really need a speed change I would suggest trying to control the second 555 with its reset line instead of the high side switch as you have it.

Move the output from the diode array from the transistor to the reset line of the 555, and remove the transistor. (and LED)

Reset line is active low…so it will run when the 4017 outputs are high, and stop when low.

 

Why not just put the LED on one or more of the other 4017 outputs to check its function? (maybe the carry out) Don't forget the resistor.

In your original description you seem to imply that you wanted a speed change on the servo between 4017 output pulses, also the schematic seems to indicate this, but when I watch the video it seems to only stop and go?

If you don’t really need a speed change I would suggest trying to control the second 555 with its reset line instead of the high side switch as you have it.

Move the output from the diode array from the transistor to the reset line of the 555, and remove the transistor. (and LED)

Reset line is active low…so it will run when the 4017 outputs are high, and stop when low.

I cant. The last timer is making a PWM signal to the servo.

For now I dont need to change the servo speed as I dont know at this point how fast it will go.

 

Ok, my bad, I was overlooking what it takes to drive a servo...was just thinking in terms of a gear motor.

 

okay so I've done what you told me to do in the other thread and that works.
I have also replaced R4 and R5 with two trimpots so I was able to adjust the position of the servo. And that works fine as well. I'd rather not have them in my final circuit though.

 

As you told me:

With trimpots:

 

okay so I've done what you told me to do in the other thread and that works.
I have also replaced R4 and R5 with two trimpots so I was able to adjust the position of the servo. And that works fine as well. I'd rather not have them in my final circuit though.

I can understand your desire not to have trim pots in the final circuit. Just a point of information, though. Hobby servos positioning is not consistent from servo to servo, nor manufacturer to manufacturer. Hence, it may be to your advantage to keep the trim pots.

A 1750ms signal applied to different servos will result in slightly different positions for each one.

I use a microprocessor library to control servos in my largest project that used the pulse width to position the horn. Since its in software, I have a table of the servos, with values for minimum, neutral and maximum signal pulse widths. And I have a function to map positions in degrees to the specific pulse width for each servo.

That’s my software. You’re controlling the servo via hardware. And thence I recommend keeping the trim pots.

 

I can understand your desire not to have trim pots in the final circuit. Just a point of information, though. Hobby servos positioning is not consistent from servo to servo, nor manufacturer to manufacturer. Hence, it may be to your advantage to keep the trim pots.

A 1750ms signal applied to different servos will result in slightly different positions for each one.

I use a microprocessor library to control servos in my largest project that used the pulse width to position the horn. Since its in software, I have a table of the servos, with values for minimum, neutral and maximum signal pulse widths. And I have a function to map positions in degrees to the specific pulse width for each servo.

That’s my software. You’re controlling the servo via hardware. And thence I recommend keeping the trim pots.

this circuit is just for one single santa jumping jack. Just for fun.

 

Ok, glad to hear.

I guess you could try to match the pot values with combos of resistors in series/parallel etc, but I don't really see any problem with leaving the trim pots in the circuit.

I have dozens of projects built using trim pots that get set once and never touched again, it's just a fact of life when having to make fine resistance adjustments.

Remember if you decide to try the "servo tester" circuit the same problem will probably happen because of the loss across the CE junction of the transistors, that needs to be compensated for.

 

@djsfantasi You just said what I was thinking and didn't quite know how to explain. Good Job! I always like to have some "tweak room" either by adjustable hardware or software. You could measure the pot ohms and match to a fixed resistor but any small variation in hardware parameters immediately puts you behind the 8 ball.

 

this circuit is just for one single santa jumping jack. Just for fun.

Just to let you know... in many of my circuits I leave trim pots in place. You never know when the servo for your Santa Jumping Jack needs replacement. If you design your circuit with fixed resistors, you may have to break down your printed circuit board to replace the resistors with new values?

My circuits deal with audio signals. I don’t want to calculate new resistor values when the audio source changes. Thus, a trim pot. Don’t tell me that your signal sources won’t change! Because in my experience they will! And then you are faced with removing soldered resistors from the PCB and either calculating or experimenting to determine new values.

I guess I’m saying that change happens.

And I’ll take a plastic screwdriver and tweak my resistance values. Done!

In the meantime, I envision you trying to desolder resistors from your PCB, maybe destroying a pad or two, patching in a trim pot to determine new values, removing the patch, soldering in new resistors, testing and cleaning up. If you’re lucky. Otherwise, you need to rebuild the entire circuit! Done!