I have a problem with unstable hot water boiler manifold valve end switches. They open and close multiple times in succession making my gas boiler go on/off each time they close and open. This isn't good for the boiler. Using a 74HC14N Schmitt Trigger to help keep the chatter under control until the end switch is closed for 10 or 20 seconds or so.

I think using diode-OR + inverters to emulate an SR latch would work.

Any ideas how I can do that?

 

Need more info.
What voltages are on these switches and how many?
So when the switch opens for the first time you want that to trigger a 10-20 second delay?
Sounds like a relay may be required as well.

 

Please post a schematic of the control circuit as it is now, and another with the modifications you are asking about. They don't have to be computer-generated drawings, just clear and legible. Be sure to add a unique reference designator (SW1, R2, etc) to each component so we can discuss them without confusion.

ak

 

A time-delay relay might be the simplest way to do what you want.

 

If this were a hobby circuit application, the previous suggestions would be good choices, BUT, SINCE THIS IS A CONTROL SYSTEM FOR A GAS FIRED BOILER, they are all poor choices because of reliability concerns. If your timer latches on for some reason, you could, at best, have an overheated boiler spraying boiling water out of a pressure release valve. Worst case would be a burst boiler.

Industrial-quality time delay relays are available from many suppliers. My favorite, currently, is "AUTOMATION DIRECT", but there are quite a few other honest suppliers. I would not trust any seller of modules found on amazon, for parts for such a critical application.

 

I have a problem with unstable hot water boiler manifold valve end switches. They open and close multiple times in succession making my gas boiler go on/off each time they close and open. This isn't good for the boiler. Using a 74HC14N Schmitt Trigger to help keep the chatter under control until the end switch is closed for 10 or 20 seconds or so.

I think using diode-OR + inverters to emulate an SR latch would work.

Any ideas how I can do that?

I am not sure what you mean by "End Switches" on a manifold. Are they thermostatic switches?? Or perhaps pressure switches??Isthis a new boiler installation?? Or a system that has been working OK for many years, but now is not?? Pressure and temperature sensor switches do fail from wear some times.
I am guessing that the gas valves are powered with 24 volts AC, that is the most common in the USA.

 

I believe it's a motorized valve that activates the switch at the End of it's travel making sure the valve is fully open before turning on the boiler.

 

Why the malfunction?
What does the manual say in the troubleshooting department?
Good luck......

 

I doubt very much that any manual would discuss that sort of problem. And it is not likely that the TS even has access to such manual. Besides that,a motorized gas valve ( with no backup closure method) is a huge invitation to a huge disaster in the event of a power failure. ( By huge disaster mean a serious explosion).
Natural gas applications need to be very reliable and FAIL SAFE!! ALL of the controls for natural gas need to be well designed. THAT is why I suggested using industrial timers from honest providers.