Small problem with a 555-timer

[Jeskaar]

Greetings.

I have recently bought myself some electronic components, and have been testing out a 555-timer. Currently, I've hooked it up in monostable mode. The problem I am having, is that the pulse won't end.

Here's the schematics.


Now, if I understand correctly, once the voltage at 2 (trigger) drops below a third of the supply voltage, the pulse starts, and stops when the voltage at 6 (threshold) is greater than two thirds of the supply voltage (at 5, control).

If my calculations are right, the pulse should end in .01 seconds. Not much, but it's the biggest capacitor and resistor I have at the moment.

However, it doesn't. I've measured the voltage at 5 to be 8 volts, and 6 to be 10 volts. Still, it doesn't end.

What am I doing wrong?

edit: Also, if someone could point me to a program where I can make schematics on my PC, I would be grateful. Doing it with MS paint isn't too practical.

 

[KeepItSimpleStupid]

Look at the following programs (free versions anyway):

1. DIPTRACE - A PC layout program
2. EAGLE - A PC layout program
3. KiCAD - An open source full featured PC layout package (totally free)
4. LTSPICE - A circuit simulation program (totally free)
5. Solid Edge - General CAD
6. Draftsight - General CAD

No particular order

 

[BrownOut]

However, it doesn't. I've measured the voltage at 5 to be 8 volts, and 6 to be 10 volts. Still, it doesn't end.

What am I doing wrong?

Nothing. You won't be able to see such a short pulse, so there is no reason to even try to measure it. The voltage at pin 3 will be "high" at the end of the pulse. It pin 3 is somewhere near VCC, then the pulse ended.

 

[SABorn]

Change the led to be between output 3 and V+ as this way the led should be off and only flash when the circuit is triggered.

Pete.

 

[SODA]

Greetings.

I have recently bought myself some electronic components, and have been testing out a 555-timer. Currently, I've hooked it up in monostable mode. The problem I am having, is that the pulse won't end.

Here's the schematics.
View attachment 50327

Now, if I understand correctly, once the voltage at 2 (trigger) drops below a third of the supply voltage, the pulse starts, and stops when the voltage at 6 (threshold) is greater than two thirds of the supply voltage (at 5, control).

If my calculations are right, the pulse should end in .01 seconds. Not much, but it's the biggest capacitor and resistor I have at the moment.

However, it doesn't. I've measured the voltage at 5 to be 8 volts, and 6 to be 10 volts. Still, it doesn't end.

What am I doing wrong?

edit: Also, if someone could point me to a program where I can make schematics on my PC, I would be grateful. Doing it with MS paint isn't too practical.

0,01 sec is the same as 1us. I bet the person that can see that fast must be a super human. Try and get hold of a 1uF cap and a 150k resistor. this will give you a 0.5 sec delay which you'll be able to see

 

[Boncuk]

Did you use a momentary switch to trigger the circuit?

 

[janagyjr]

Look at the following programs (free versions anyway):

1. DIPTRACE - A PC layout program
2. EAGLE - A PC layout program
3. KiCAD - An open source full featured PC layout package (totally free)
4. LTSPICE - A circuit simulation program (totally free)
5. Solid Edge - General CAD
6. Draftsight - General CAD

No particular order

I prefer TinyCAD myself.

SourceForge.net: TinyCAD - tinycad

 

[Jeskaar]

Look at the following programs (free versions anyway):

1. DIPTRACE - A PC layout program
2. EAGLE - A PC layout program
3. KiCAD - An open source full featured PC layout package (totally free)
4. LTSPICE - A circuit simulation program (totally free)
5. Solid Edge - General CAD
6. Draftsight - General CAD

No particular order

Thank you, I will check them out.

Did you use a momentary switch to trigger the circuit?

Yes.


Thanks for your help, guys. I realize my mistake. Initially, I thought the pulse would start counting immediately as pushed the switch, and I would see a short flash. Obviously (now anyways), it won't begin until the switch is released, and is way too short to see.

Cheers.