Need help with 555 timer circuit

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fonddeath55

New Member

• Aug 12, 2009

• #21

I checked pins 2 + 7 and their not shorted but i did cut the pin 7 connection and it doesnt change anything. but now it doesnt ocsilate it just stays on red and sounds the buzzer. can anyone help me turn it off after it sounds red after like 10 + more seconds to save the battery

 

Last edited: Aug 12, 2009

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fonddeath55

New Member

• Aug 12, 2009

• #22

i checked the pdf and it says this: The circuit starts timing when switched on. The green LED lights to show that timing is in progress. When the time period is over the green LED turns off, the red LED turns on and the bleeper sounds.
Doesnt this mean it wont turn off... after awile..

 

Last edited: Aug 12, 2009

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BrownOut

Banned

• Aug 12, 2009

• #23

It's not designed to trun off. You have to turn it off.

 

marcbarker

New Member

• Aug 12, 2009

• #24

What's supposed to happen is you switch in on, the green is LED on and there's a time period...... Then when the time ends: beep + red LED. It'll stay this way, until either it's turned off, or battery runs flat.

I'll take a guess that you want just a short beep only. You can insert a very large capacitor in series with the beeper. The bigger the cap, the longer the beep.

 

Last edited: Aug 12, 2009

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fonddeath55

New Member

• Aug 13, 2009

• #25

So would these be the right layout. And what size cap would you recomend for 5-10 seconds or around there.
**broken link removed**
And that part was out of this part of the schematic
**broken link removed**

 

Last edited: Aug 13, 2009

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fonddeath55

New Member

• Aug 13, 2009

• #26

so i checked it out and i built the circuit but the capacitor has to connect to the red led and the positive. But the thing is after it goes i have to discharge the capacitor. I know i can add a momentary switch but im wondering if i can attach it to somthing so i wont have to discharge it manually

 

Last edited: Aug 13, 2009

audioguru

Well-Known Member

Most Helpful Member

• Aug 14, 2009

• #27

A diode in series with a resistor (limits the discharge current to 100mA) will discharge the capacitor when the output of the 555 goes high.

Increase the value of the series capacitor to increase the time the bleeper makes noise.

All electronic circuits should have a supply bypass capacitor. I used 100uF.

 

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colin55

Well-Known Member

• Aug 14, 2009

• #28

You haven't explained clearly what you want to do.
Do you want a circuit that sits around, taking very little current, and when you push a button, a piezo diaphragm emits a tone for a approx 1 second, after 10 seconds.
The circuit then stops and consumes very little current.