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Circuit help

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Jony130

Active Member
In your circuit, you can not get the TL = TH. You have to add a diode, as in my schematics
Diode are 1n4148.
 

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audioguru

Well-Known Member
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1) You have 8V worth of LEDs but the output high voltage of the 555 is 7V with a brand new 9V battery which drops lower and lower as it is used. So the LEDs will not light.
2) The datasheet for the 555 (NE555, TL555 or LM555 shows the parts values for any frequency.
3) Every IC circuit powered from a little battery needs a supply bypass capacitor (use 100uF).
 

Boncuk

New Member
1) You have 8V worth of LEDs but the output high voltage of the 555 is 7V with a brand new 9V battery which drops lower and lower as it is used. So the LEDs will not light.
2) The datasheet for the 555 (NE555, TL555 or LM555 shows the parts values for any frequency.
3) Every IC circuit powered from a little battery needs a supply bypass capacitor (use 100uF).
He doesn't source the LEDs but sink.
 

audioguru

Well-Known Member
Most Helpful Member
He doesn't source the LEDs but sink.
Yes. But the output voltage loss is even more for sinking.
The saturation voltage loss of a 555 when it sinks 100mA is typically 2.0V but could be 2.5V which is its max.
 
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