Led flasher circuit (ne555n)

Thread Starter

lubnaan90

Joined Jan 13, 2010
198
Planing to make a led flasher circuit out of NE555 ,
My question is,is it possible to make the circuit work on a 14volt , 0.5 amp transformer.
Do i need to change the POT or any other components .
Any help will be deeply appreciated.
 

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beenthere

Joined Apr 20, 2004
15,819
The device is only able to operate with a DC voltage. You will need to rectify and filter the transformer output (unless it's a DC wall transformer).
 

Thread Starter

lubnaan90

Joined Jan 13, 2010
198
The device is only able to operate with a DC voltage. You will need to rectify and filter the transformer output (unless it's a DC wall transformer).
Ofcourse , i am using a rectifier chip , like the one shown below .i have etched a special place to solder the same on the PCB.
 

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Thread Starter

lubnaan90

Joined Jan 13, 2010
198
i have almost finished etching , will clean the pcb & solder components with in 5 mins , will keep updated .
 

Thread Starter

lubnaan90

Joined Jan 13, 2010
198
DONE !
finished making the circuit ,
seems something is wrong ,
The circuit seems to work fine (Led Blinking) on a 12v .5amp wall DC adapter.
but doesnt seem to be working (led not blinking , just steadily lit) on the transformer (14v .5amp) .
Note: I have used the rectifier but not used a filter (since i dont have a capacitor wth me now) , can that be the problem ?
 

SgtWookie

Joined Jul 17, 2007
22,220
The circuit will not work without the capacitor.

If you are using a 14VAC transformer, you must also use a voltage regulator after the filter capacitor, or you will quickly burn out your 555 timer.

I will guess that you will have about 19v to 24v on the filter capacitor, which is over the limit for your timer.
 

bertus

Joined Apr 5, 2008
20,893
Hello,

Without the buffer capacitor the DC voltage afther the rectifier will be pulsed.
The 555 is every time starting again.
You say you want to use a 14 Volts transformer.
Use a 1000 uF / 35 Volts capacitor as a buffer.
The rectified and buffered voltage will be about 1.4 X higher, so 14 X 1.4 is about 20 Volts.
The maximum voltage for a 555 is about 15 Volts.
You could use a LM7812 to stabelize the volatege back to 12 Volts.

Greetings,
Bertus
 

Thread Starter

lubnaan90

Joined Jan 13, 2010
198
Hello,

Without the buffer capacitor the DC voltage afther the rectifier will be pulsed.
The 555 is every time starting again.
You say you want to use a 14 Volts transformer.
Use a 1000 uF / 35 Volts capacitor as a buffer.
The rectified and buffered voltage will be about 1.4 X higher, so 14 X 1.4 is about 20 Volts.
The maximum voltage for a 555 is about 15 Volts.
You could use a LM7812 to stabelize the volatege back to 12 Volts.

Greetings,
Bertus
Thank you all for your interest
Can I use L7812C Instead of LM7812 ?
 
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