In the double action condition, does it close the same contact twice for the 'engage' action, if so the single micro would be simple, but even so, if double contact, it should be easy to make up a double switch arrangement, particularly as there is a single actuator through the middle.
Is it possible to post a pic of the switch?
Max.

I can't do anything to a switch itself, but i can put a different switch on the panel and solder it the board in parallel to the original.

 

Is the existing button only switching logic-level voltages, or something higher?
Is the button switch NO or NC?

 

Is the existing button only switching logic-level voltages, or something higher?
Is the button switch NO or NC?

Logic level, NO

 

I've also found this diagram. Can someone explain to me the other 3 gates do on this one?

 

It is just creating an exclusive OR gate using four NAND gates.

Les.

 

Heres an idea:

2 555s, first one configured as a one shot and the second one is for square wave generator. The trick is to get the timing just right for 2 pulses. You'll have to calculate the timing value as this is just for demonstration:

 

Heres an idea:

2 555s, first one configured as a one shot and the second one is for square wave generator. The trick is to get the timing just right for 2 pulses. You'll have to calculate the timing value as this is just for demonstration:
View attachment 182018

Except it will create a series of pulses for as long as a button is pressed, which isn't ideal. I think i'm going to stick with a XOR. Here's the final design. Any thought?

 

Except it will create a series of pulses

No it does not.

 

I would put a low value resistor (A couple of hundred ohms.) in series with either SW1 or C1 so you do not create a negative pulse on the 5 volt rail when SW1 is pressed. (You are trying to charge C1 instantly so it will pull a large current for a very short time from the 5 volt rail.)
I am assuming that you are using a CMOS XOR gate. I'm not sure if your relay drive circuit will work as the base current will be less than 1 mA and the minimum hfe value for BD139 is only 25. It may work if you can find a relay that requires a very low current. I would use a small mosfet such as a 2N7000 which should be OK for a relay that requires up to about 100 mA.

Les.

 

I don't know of a CMOS XOR gate that can drive 24 mA output but even if it does you have a 5 K resistor between it's output and the base of the BD139.

Les.

 

I am assuming that you are using a CMOS XOR gate. I'm not sure if your relay drive circuit will work as the base current will be less than 1 mA and the minimum hfe value for BD139 is only 25. It may work if you can find a relay that requires a very low current. I would use a small mosfet such as a 2N7000 which should be OK for a relay that requires up to about 100 mA.

Les.

I was going to use this 40mA relay with this cmos gate. This should be better then.

 

Depending on the timing and input characteristics of your equipment, here's a possible solution using a microswitch (as Max suggested) :

 

My idea for one version would be to use a similar miniature Microswitch as in #11 and use a Telemecanique ZB2B P.B. SW body, the switch sections themselves would not be required, these have a metalic body and the ordinary illuminated PB head has a 1/2" dia hole in it where a short length of hardwood dowel could be inserted, a small notch in the dowel would activate the M.S. when pushed it would be off-on-off, the same on release, the PB itself has a spring return.
The stroke however is only 3/16" so the notch would have to be such that gives the right off/on/off sequence.
This would preclude the need for extra electronics.
Max.

 

So i've finally got around to building a pcb. Seems to work fine. Just had to add couple filters for the noise .




UPDATE
Tested it in the equipment. Worked but inconsistently. Pulse width probably too short. Replaced the XOR gate with a sequential timer on three 555's. Works like a charm.



Link to EasyEDA project:
https://easyeda.com/vadim_1133/seqtimer