Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Other Topics => Topic started by: rzenc on July 10, 2012, 09:42:26 am

Title: LED timer
Post by: rzenc on July 10, 2012, 09:42:26 am

Hi there,

So, I was asked to built a kind of toy...a push button which turn on a led for about 10s and then it should come off....well, I did in on the protoboard and it worked...build a prototype and it worked...

I gave it to a friend...it's working fine...

Another friend saw it and wanted one too...instead of making another PCB, I decided to build it on the protoboard again in order to check current flow on components and to my surprise..it doesn't want to work anymore... :help:

It turns on but never comes off....

Schem is attached...I used guidelines from LM555C to make a monostable circuit...the actual chip is NE555N

I have fooled around with different combinations of R & C but no joy yet...either it works for about 1.5s and shuts off or it just never turns off...it's driving me mad...

Links to both datasheet of 555 chips

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000479.pdf (http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000479.pdf)

http://www.ti.com/lit/ds/symlink/lm555.pdf (http://www.ti.com/lit/ds/symlink/lm555.pdf)

Can you guys help me out?? don't know where to look since I have limited experience with SS and chips...

Thanks in advance for all

Best Regards

R.

Title: Re: LED timer
Post by: sluckey on July 10, 2012, 11:08:44 am

Where's your timing cap???

Wire it like this...

(http://www.eleinmec.com/figures/004_02.gif)

Title: Re: LED timer
Post by: rzenc on July 10, 2012, 12:41:43 pm

Where's your timing cap???

I may have deleted it accidentaly...

I will try your suggestions

THANKS Steve :worthy1:

Best Regards

R.

Title: Re: LED timer
Post by: rzenc on July 10, 2012, 02:19:16 pm

Thanks a lot Steve!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

It's not only working, but also got a plus since the other circuit was lighting the LED's when first turning it on....and now it doesn't until I hit the button!!!

GOD SAVE STEVE!!!!!!!!!!!!!!

Best Regards

R.