Still no schematic, so this might be wrong. A 555 astable circuit powers up with the output in the high state . . .

1. Is this a requirement for the replacement circuit? I ask because after a POR, the CD4060 powers up with all outputs in the low state.

2. How much current does the power switch have to switch?

My preliminary schematic is ready; just waiting to see what you have.

ak

 

A 555 astable circuit powers up with the output in the high state . .

If you connect the timing capacitor to V+ instead of ground, it should power up with the output low.
After that it will operate normally.

 

If one of the basic requirements is "simplicity" I can't see how learning to code meets that requirement.

I assume "simplicity" refers to the circuit complexity, not what it takes to do the design.

 

If you connect the timing capacitor to V+ instead of ground, it should power up with the output low.

Agree, but I think it is a safe assumption that the TS circuit is not like that. Although, it has been 23 posts and we still do not know much about it.

ak

 

Ok, just tooling around and wanted to see if I could actually still do this kind of thing.

This is only a proof of concept, not a finished design.

In my original concept the voltage-controlled switch would be replaced with a DPDT relay as to accommodate whatever the "Main Power Switch" is and have a second pole to light the LED with whatever power source is available after each cycle.

The relay would be switched by a single NPN but LTSpice won't let me switch the Voltage-Controlled switch via the low side.

What I mostly wanted to proof was getting the first cycle of the 555 as close to the rest of the following cycles as possible, but I really didn't want to push the limits, so I settled for what you see here...just a small fraction of a second longer.

The time is set to about 30 seconds for each segment, but I understand the OP wants a variable time. The pot and limit resistor would replace R1. (R2 can be reduced but I don't see the need)

The total time would be available at the relay and the output of the 4072. The segment times would be available at the 4017 outputs.

And I really can't guarantee that this circuit would work in real life because the subcircuits I have are powered all the time, and I really don't have the time or expertise to change that, but I will bet that the basic principle will work.

 

I assume "simplicity" refers to the circuit complexity, not what it takes to do the design.

Well, we all get to make our own assumptions...right?

 

Well, we all get to make our own assumptions...right?

Right.
I try to make the most logical assumptions, which I assume you also do.

 

What I mostly wanted to proof was getting the first cycle of the 555 as close to the rest of the following cycles as possible,

Because the timing cap is grounded and starts at zero charge, the first half-cycle, during which the output is high, will be about 30% longer than all of the subsequent high half cycles. You can minimize the effect this has on the overall output frequency by making the high half-cycle periods very short relative the the low half-cycles periods.

The same is true for the oscillator in the CD4060, but because the Q10 output frequency is 1/1024th the oscillator freq, any anomaly in the very first half-cycle is trivially small compared to the output waveform periods.

ak

 

You can minimize the effect this has on the overall output frequency by making the high half-cycle periods very short relative the the low half-cycles periods.

That is exactly what I did, I got the first half cycle down to a very small fraction of a second.

But you can't do that with the standard timing configuration.

 

But you can't do that with the standard timing configuration.

Here's a modification that starts the oscillation with the output at 0V, and sets the initial cap voltage at startup to minimize the first half-cycle effect.
Interchanging R4 and R4 (and inverting the timing capacitor polarity) will have the same effect, but it will start with the output high.

 

The first impression I got was that the TS already had the pulser working and wanted to add this additional feature. The second impression I got was that this is a one-off personal project.
If this is a product development then commercial consulting rates apply!!!

 

@crutschow

Did you mean R4 and R5?

I'm curious...where would you place a pot/VR to change the frequency?

 

Did you mean R4 and R5?

Yes, excuse the typo.

where would you place a pot/VR to change the frequency?

R2, as would be usually done.
My addition has no effect on the normal operation of the 555, it only sets the initial condition.

 

I see...good tip.

 

My addition has no effect on the normal operation of the 555,

True, as long as the Thevenin equivalent of R4 and R5 is much lower than the timing resistor values. It appears in series with R2.

I've seen some strangely complex circuits trying to deal with the first half-cycle issue. This is better.

ak

 

I've seen some strangely complex circuits trying to deal with the first half-cycle issue. This is better.

Simplicity has it limits.
The caveat is that it only works for startup from zero supply voltage, not for using the Reset pin to start and stop the oscillation.

 

Thanks a lot everyone for your opinions and contributions, and with all due respect I'm trying to avoid microcontroller.
Please allow me to re-phrase my query.
I already have my circuit working perfectly but in continuous mode. What I wonna do is to have it working automatically like so:
1. Once i switch the main power switch it works for 30 (or 40) minutes then cut-off the output for 10 or 20 minutes.
2. It will repeat that cycle for 4 times
3. At the end of the 4th "On" period it should come to full stop until I reset it (or manually switch off the main power)
It's more or less similar to the washing machine programs. It stays powered on but no operation.. only a small LED indicating the program has finished.

What I initially had in mind is to do these on/off timings with a 555 (bad choice I know) where I would control the input power to the circuit to get the required On & Off times and was only looking for a way to get it to full stop after 4 cycles again by controlling the input power to the circuit.
Hope it's more clear now so all suggestions are welcomed.
Thanks again to all.

 

If the 15 volt supply will stay on, then the solution is fairly simple. use a CD4017 counter IC to count the pulses, and when the count of 4 is reached then the output switches off the power mosfet. Then to start it over, a momentary pulse to the reset of the 4017 resets the counter. You may need to invert the 555 output to the 4017 so that it will switch off when the fourth pulse ends.

Yes the 15V supply is always available and please look at my latest post where I re-explained exactly what I wonna do. Also using the 555 to control these timings is not a necessity.. any other simple ideas are welcomed. Thank you

 

If one of the basic requirements is "simplicity" I can't see how learning to code meets that requirement.

Now if the OP already knows how to code then the suggestion to use a micro is like telling a carpenter to use a hammer on the nails.

Of course, someone can provide the code, but that is something I rarely see working out very well.

You read my mind... got no time or in a mood to start learning codes.

 

Still no schematic, so this might be wrong. A 555 astable circuit powers up with the output in the high state . . .

1. Is this a requirement for the replacement circuit? I ask because after a POR, the CD4060 powers up with all outputs in the low state.

2. How much current does the power switch have to switch?

My preliminary schematic is ready; just waiting to see what you have.

ak

I may have badly explained what I need, I added another reply with full details. Also the attached diagram may better explain the requirements