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Simple 555 Timer

am.steen

Jul 10, 2023
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this staircase automatic timer drives me creasy as it is very simple but not working

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when power the circuit the Bulb becomes on without press S1 or S2 buttons
what I do
1. removing NE555 from its socket then apply power the bulb is off.
2. replacing the 555 IC and TRIAC but same problem bulb is on.
3. I connect a led and resistor to pin 3 of 555 and power the circuit the led is off then press S1 the led is on for timer period then off ( the Bulb is always on ) this means 555 operation id right.
note
R1 was 10k in original circuit but with this value the 555 triggered from it self ( also with R1=10k the bulb was on ).

What is the problem ??
Or if anyone have a tested staircase timer with TRIAC schematic please send it.
 

crutschow

May 7, 2021
861
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May 7, 2021
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What is a "staircase timer"?
What is the purpose of the 555?
What exactly do you want the circuit to do?
 

crutschow

May 7, 2021
861
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May 7, 2021
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when power the circuit the Bulb becomes on without press S1 or S2 buttons
Why is that a problem?
Is the power not applied continuously to the circuit?

Try connecting the positive side of C2 to the V+ supply, and the negative side to pin 6 and R3.
Also change R1 back to 10kΩ.
R3 is not needed--you can connect pins 6 and 7 together.
With that the 555 should power up with a low output.

Be aware that one leg of the 220Vac is connected to the push-buttons.
 

bertus

Moderator
Nov 8, 2019
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Hello,

I see that the origenal circuit asks for a BT136
You are using a BTA08, wich has a much higher gate current.
Compare the datasheets I attached.

I have also attached a collection on application notes in one PDF for Thyristors and Triacs.

Bertus
 

Attachments

  • BT136-600E.pdf
    162.1 KB · Views: 1
  • BTA08.pdf
    288.2 KB · Views: 2
  • AN1001_AN1010_PowerThyristorApplicationNotes.pdf
    949.7 KB · Views: 2

Bluejets

Oct 5, 2014
7,041
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Be aware that one leg of the 220Vac is connected to the push-buttons.
This is the part that concerns me........... Not a good idea by any means and more likely than not, violates any building code.
Be prepared to face a grilling and other consequences if it ever goes belly up and electrocutes someone.

My advice would be to strongly suggest you forget it and buy a commercial product designed for the job.
..............and get a qualified lecky to fit it as well and save any house insurance queries.
 
Last edited:

Alec_t

Jul 7, 2015
3,638
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Jul 7, 2015
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3,638
Your use of a 10k/10W dropper resistor would be a concern for me. It will dissipate nearly 6W and get HOT. It's a fire risk and not eco-friendly. It will cost more to run than the bulb.
Perhaps a mains-rated 6W LED bulb could replace the whole circuit and be left on permanently?
 
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