spark causes my timer to reset?

[skmdmasud]

I made a timer circuit using the following

**broken link removed**

and added a digital wrist watch which has its alarm output using a transistor connected to the reset to reset the circuit at a defined time. In this way i can start my timer and the timer itself stops using its own timer.

My circuit **broken link removed**

when the timer expires it DE-energises the relay and stays off. Everything is working fine so far but i have notices when the relay is in DE-energized mode any sparks formed by inserting/removing plugs in multiplug(220V ac) causes the timer to reset by itself. I know that spark is a noise in the line so how do i filter it or do something so that my circuit stops this behavior.

 

[mvs sarma]

manage a spark quench comprising of a resistor and capacitor in series across the relay contact and it helps to quench the spark., (say 0.01uF630V Polyester capacitor and 220 0hms 1watt) CAUTION beware of shock hazard

 

[alec_t]

All those lengthy wires will act as antennae and pick up stray EM radiation (from mains appliances switching on/off etc). Make everything neater, more compact and enclose your circuit in a screened housing.

 

[skmdmasud]

mvs sarma i think you are a plugin which generates answers by searching different place.
alet-c you are may be correct i will test my circuit for interference.

 

[mvs sarma]

nothing like that.
I had exposure to electronics and telecom for over 39 years and spark quenchs are extensively used by most telecom manufacturers.
Perhaps A sudden reply from me might make you think like , i have Googled and put up some bla bla.

 

[audioguru]

The relay contacts have nothing to do with the problem. It is the messy wiring that causes the problem.

When the relay is de-activated (not doing anything) then sparks caused by other electrical products or inserting/removing other AC plugs causes the circuit to reset.

 

[skmdmasud]

My apology Mvs Sarma your answer seemed different. As others have said relay is off so there is no spark from relay coils turning on off etc.

alec_t and audioguru can i use my mobile phone to test for interference since it creates huge amount of radio wave while making calls. I will shorten the wires first and use some more pcb for those hanging components lol.

Thanks.
Masud.

 

[mbarazeen]

reduce the resistor 100K (R6) that is connected from reset to ground, may be you can try with 10k. also add 104pf across C1. it may solve your issue..

Edit: connect 104 pf very near to pin#16 and to ground.

 

[audioguru]

Most cell phones in my country work on extremely high microwave frequencies that are much higher than a simple electrical spark.
Maybe in your country cell phones still use fairly low frequencies like sparks.

Your problem is caused by sparks so you should use sparks to see if your re-wiring fixes the problem enough. Maybe your circuit needs a shielded enclosure.

 

[skmdmasud]

reduce the resistor 100K (R6) that is connected from reset to ground, may be you can try with 10k. also add 104pf across C1. it may solve your issue..

Edit: connect 104 pf very near to pin#16 and to ground.

Thanks a lot for the modifications mbarazeen. Inshallah I will try it out ASAP.

 

[skmdmasud]

Most cell phones in my country work on extremely high microwave frequencies that are much higher than a simple electrical spark.
Maybe in your country cell phones still use fairly low frequencies like sparks.

Your problem is caused by sparks so you should use sparks to see if your re-wiring fixes the problem enough. Maybe your circuit needs a shielded enclosure.

cell phone in our country uses GSM 900/1800 MHz, i think your country uses the same if its GSM. I think mbarazeen solution will work since it has to do with reset only.

 

[skmdmasud]

My light timer in box and labeled.


**broken link removed**