[SOLVED] designing an alarm clock circuit

[milan.rajik]

I observed RTC running 5 minute back per day in clock.that means accuracy of a rtc is not good.How to solve this type of problom.Please reply.

DS1307 doesn't vary 5 minutes a day.

If you need precision clock use DS3232.

 

[tapu]

Dear all,Thank you for replies.above problom have solved.
Now I want to know how to generate second pulse in ds1307.& how to program in AM/PM mode, becouse it is in 24 hour mode.

 

[arun_190175]

Dear all,Thank you for replies.above problom have solved.
Now I want to know how to generate second pulse in ds1307.& how to program in AM/PM mode, becouse it is in 24 hour mode.

enable sq bit in cantrol res and set rs0,rs1 for requred fq.

 

[tapu]

But how to enable control register in ds1307.I am confusing aout it.

 

[arun_190175]

read data sheet and this is like as other regs.

 

[ud23]

**broken link removed**

 

[arun_190175]

 

[tapu]

Dear All,
Thank you for replies.above problom have solved.Now I am facing one series problom.Here I am using 230v AC electeric bell for alarm.(according to its use) & 12v dc relay for switching.When bell rings & stop then clock stops & keypad also not work.seems controller hanged.Please reply.

 

[arun_190175]

i think this is due to back emf problem try to use diode or 47uf near relay

 

[ud23]

surely back emf problem you can try the mov(variestor) at the relay output.

 

[tapu]

Dear All,
is varistor or diode is diectly conneted to relay output to controll back emf? where AC voltage is their in on state.My relay circuit is given in post 7.

 

[ud23]

https://www.phoenixcontact.com/assets/downloads_ed/global/web_dwl_technical_info/105396_en_00.pdf

 

[tapu]

That means my problom mentioned above is becouse relay circuit is not protected.As I connect relay direcly to the load.

 

[ud23]

yes dear tapu if you want to debug and know try with the isolated power supply for your 12v relay from controller supply.I was also doing like you connecting relay with load with out protection and then i realized that very freaky noise level at industry world so need to protect our device.

 

[tapu]

Dear ud,only varistor is enough or RC circuit is required for protection?

 

[ud23]

IF its bell then varistor (MOV ) do the job i guess

 

[tapu]

Dear sir,Now I add protection to relay as you advised.Here I am using same power supply for microcontroller circuit & relay circuit.is it ok?

 

[ud23]

ya you can try with same power supply.

 

[tapu]

Dear sir,Before this thread I studied snubber also in google. can i add snubber with varistor for more protection Or varistor is enough in relay output?

 

[ud23]

just try with the MOV first and check the result then go further.Go step by step its good to avoid put unnecessary components.