Hello everyone,
I hope someone can help me with this.
I want to build a circuit, which I think will be based around a 556, where the power is continuously applied, and when a button is pushed to trigger the 556 two pulses (to switch relays) are produced.
The first pulse happens immediately, and is about 0.5s in lenth, the second happens about 2s later again with a pulse of about 0.5s.
This would be wether the trigger button is held down or just 'jabbed'
I can't seem to find just the right circuit on the net, hoping someone here can help.

Many thanks in advance

Karl

 

You have got three times to er.. time, so you need three timers - perhaps a '556 and a '555.
What do you want to happen if the button is pressed a second time before the sequence has ended?

 

If the button was pressed before the sequence had completed, my preference would be it was ignored, but if it started the sequence again that wouldn't really be much of a problem.

Thanks

 

Deleted circuit.
Did not meet the OP's requirements.

 

Are the two pulses on one output line, or one pulse each on two separate wires? For separate output wires, I did a dual pulser circuit for an AAC thread in September, 2015. Let me find it and update it. Rather than staged timers, it had one output timer that was directed to one of two output lines, so the two pulses were guaranteed to be the same width, and adjustable by changing only one resistor.

ak

 

Here is a quick cut of a first rework. Input monostable, diode or logic, output monostable, diode steering, outputs. One CD40106 hex inverter, lotsa other stuff.

U1A and B form the input 2-second monostable that locks out the input while timing. U1E and F form the 0.5 s output pulser. The start of the 2 s pulse drives the output pulser through D2, and the end of the 2 s pulse drives the pulser through D3. D5 and D6 enable the appropriate output driver.

ak

 

OK, here is a more simple version. In this one, the two output pulses have independent timers. The circuit uses a single CD4093 quad NAND w/ hysteresis.

Edit: R1 should have a 1N914 diode in parallel with it to shorten the recovery time between cycles.

ak

 

This would be wether the trigger button is held down or just 'jabbed'

I think I may have misinterpreted your statement.
Do you mean you want both pulses, independent of how long the button is pressed?
Or do you want the second pulse only when the button is held down?

 

If you are familiar with small 8 pin μchips, you could do it very simply with very few components.
12f1822, at low cost and small footprint..
Max.

 

Both when it's given a short press and when it is held down.
Just to confuse matters first push on press & 2nd on release would also work.

Thanks

 

Both when it's given a short press and when it is held down.
Just to confuse matters first push on press & 2nd on release would also work.

Those are two contradictory condition sets. The second pulse can be timed (to 2 seconds or whatever) after the start of the first press, or tied directly to the release of the first press. You can't have both.

Please choose.

ak

 

Both when it's given a short press and when it is held down.
Just to confuse matters first push on press & 2nd on release would also work.

Thanks

May I ask why? For what is this logic applied to?

What are you going to be controlling with that logic? I'm almost certain that if us would know that then we could possibly find a suitable solution.

Edit: controlling some relays without known purpose doesn't help

 

May I ask why? For what is this logic applied to?

What are you going to be controlling with that logic? I'm almost certain that if us would know that then we could possibly find a suitable solution.

Edit: controlling some relays without known purpose doesn't help

When the button is pushed, a solenoid is operated for about 1/2 sec, the about a second later a 2nd solenoid is operated for about 1/2 sec.

Thanks

Those are two contradictory condition sets. The second pulse can be timed (to 2 seconds or whatever) after the start of the first press, or tied directly to the release of the first press. You can't have both.

Please choose.

ak

Yes, that post of mine was a poorly written, ideally what I am after is that the sequence runs through after first trigger regardless, but if a running sequence restarted at a trigger that would not be a deal breaker

 

can't seem to find just the right circuit on the net,

A few 555 or nand gates will do.

But it would be a perfect job for a MCU.

 

A few 555 or nand gates will do.

But it would be a perfect job for a MCU.

I was trying to keep it very simple, battery powered & low cost (<£/$10)

 

I was trying to keep it very simple, battery powered & low cost (<£/$10)

a mcu-based solution would be very simple and of low cost - a mcu plus a button and maybe a capacitor is all you need.

Obviously, you will need to know how to program the chip and maybe associated hardware if you don't already have them.

here is one example of how it could be done with a mcu (a pic12f675 here):

1. The input pin is on GP0, active low. I enabled pull-up here to save a resistor. An optional capacitor can be put on the line to counter any transients.
2. Once the input is asserted on GP0 (=it goes low), the first output (GP1) is asserted for 100ms, regardless of if the input is still asserted;
3. Once GP1 goes off, the mcu will wait about 500ms, and then assert the 2nd output (GP2) for 100ms.

and the life goes on from there.

I picked those timing parameters for each of simulation but it can be practically anything you want them to be.

Depending on the chips you pick, getting it done with $1 is entirely doable.