Hi. This is my first time posting at electro-tech-online. I have a fairly simple question for the more advanced electronics afficianados. Here's my question. I have a schematic for a blinking led that runs on a 555 timer chip. The schematic checks out. However I went to lay out five of them in a parallel array and things got screwy. Basically two or more LED's would go off or on at the same time much more often than one would expect to be chance. It's a very slow blink rate so its easy to notice when they swich. I want them to operate as individual lights. The blink rate for each LED is uniform and periodic and is slightly different from the blink rate of the others.
So basically .. how could I better wire a multiple LED array for unsynchronised blinking lights?
Also.. is there software out there where I can test the response of the LED's in a simulated environment?
hi,
If the 555's are the older TTL type, they can 'inject' noise into the power supply rail, when their output pin #3 change state.
You should always have decoupling capacitors, say a 100nF near the 555 across pin#8 and pin#1 of each 555. also say a 47uF or higher across the supply rails.
hi,
They are the +V supply and 0V supply wires. For a battery supply thats, +V terminal and the -V terminal [ the -V terminal is considered to be 0V reference]
Those are the 555 IC pin numbers. pin #1 is 0V and pin#8 is +V
Hello. I just noticed something. In my email auto notify the message says..
(1st)
"You should always have decoupling capacitors, say a 100nF near pin#8 and pin#4 of each 555. also say a 47uF or higher across the supply rails."
But in the forum it says..
(2nd)
"You should always have decoupling capacitors, say a 100nF near the 555 across pin#8 and pin#1 of each 555. also say a 47uF or higher across the supply rails."
So I drew two drawings under the first instruction from email. One of them has the 47uf cap inside the individual led circuit and the other drawing it's outside. Im not sure which one is the way to do it since both have 47uf caps connected to 0V and +V.
Pin 4 is normally tied to pin 8.
Then a .1 ufd. from pin 1 to 8 and a 47ufd. also from pin 1 to 8.
It is also good practice to add a .01ufd from pin 5 to ground. (pin1)
Here's what I have. (Attachment) I'm new to electrical forums where people ask for advice. So this is a big relief for me that I was able to find others who are willing to help who are knowlegable. I'll add a star to your reputation(s).
I had a problem posting, I noticed that I had pin#4 instead of pin#1, I edited the post, but the posts disappeared and I got into a 'post' loop. I hope the multiple posts didn't cause you too many problems.
Oh hey! Thanks for the input Mr RB. I had been away from the project for quite some time and had not scrolled down in my emails to see there where reposts on the topic.
I had tried the circuit as described but I was not able to un-couple the LED array even with different orientations of the caps. I'm not sure what to do. This was the first circuit I designed and perhaps I could make it work with the 7414 IC.
Actually second thought. It appears that the 7414 would not give that unsyncronised effect that a series of multiple 555 timers would give. Is this a fair assumption? I would be interested in any ideas even if it meant I would have to revamp and rebuild the circuit. Thanks.
Why don't you use a pic16lf628 with a pseudorandom algorithm , can drive up to 16 LED without other external components except the limiting resistors for LED-s. I'm sure somebody will help you with a simple program for it
Im thinking I'm going to try to stick to the original suggestion by ericgibbs.
Mr RB: Thanks for the input I'll keep it in mind. I may decide to switch over.
M Dorian: That's another good idea I'll also keep that in mind however I dont think I'm at that skill level just yet.
Audioguru: I'm posting the current up to date drawing. Within it are 5 caps of each type. There are 5 LEDs in parrallel listed under "(A)". You mentioned that only one 47uf and one 0.1uf is nessisary. Im not sure where they go. I would guess: around the battery. However I'm not sure.