Problem with parallel 555 Timer Circuits

[ChuckW]

I have built several 555 timer circuits to drive flashing LEDs on a model railroad layout. They work fine when powered separately but don't play well together when connected in parallel to a 9VDC power supply. The flash rates speed up considerable when more than 1 circuit is connected to the PS. Is ther a way to isolate the circuits from each other yet power them from the same PS?

 

[ronv]

There are several possibilities because they should work. Probably the first thing to make sure of is that you have decoulpling capacitors on the 9 volts to ground. The second is a small cap on the control voltage pin. The third is neat wiring. Maybe a schematic is also in order. There is a lot of info in most 555 datasheets.

Battery or power supply???

 

[audioguru]

A new 9V alkaline battery can supply a few hundred mA for a few minutes.

A 555 causes a 400mA supply current spike (as shown on Intersil's datasheet for their Cmos 555) when its output switches high or low. Supply bypass capacitors are explained on the datasheet of the LM555 and they show two in parallel to help prevent interference to other circuits using the same supply.

Maybe your 9V battery is old and its voltage drops to nothing when the 555 output switches and tries to draw 400mA.

 

[ChuckW]

Thanks for your prompt reply. You were right on the mark. A 0.1 μFD capacitor across the power inputs solved the issue. All the flashers are playing together nicely and working exactly as they did on the workbench.

 

[307pavlos]

Would you mind to post your circuit here or send it to me by email? Just for education purposes, as i'm studying electronics! thank you in advance my friend!

 

[ChuckW]

The circuits I used were taken from this web site: https://www.555-timer-circuits.com/

 

[colin55]

All these circuits https://www.555-timer-circuits.com/
have been taken from my website without my permission.


Colin Mitchell

 

[Ian Rogers]

Not copyright 6-7-2011 Colin Mitchell You can copy and use anything.

Colin55... this is at the bottom of your website...

 

[Mikebits]

Colin55... this is at the bottom of your website...

LOL...

Obviously you have put an inordinate amount of work into to you website Colin, but do you honestly claim it all to be your original work?

 

[nickelflippr]

Interesting debate. Regardless of whether the circuit diagram is original or not, the artwork and photos out to be copyrightable. If someone clones your webpage art and descriptions, are they not stealing searchable web hits and traffic from you. Colin should have copyrighted his web page.

 

[audioguru]

It costs a fortune to fly to the copying country, hire a lawyer, stay in a hotel and sue somebody who might not have any money.

 

[nickelflippr]

I saw recently where a prominent Chinese electronics website, copied a U.S. company's description of a provided serivice. The service description, table of materials, units of measure were ripped directly from the site, of course the cost was considerably less, that is the way the world works nowadays .