Need more power with 555/4017b

Thread Starter


Joined Nov 22, 2008
I am using a 555 counter and a 4017B to activate both running lights and sounds associated with each light. I utilize ten 31a transistors. I am using two 6v lantern batteries to power everything. I need more power for my display. Can I use two separate power supplies? one for the ic's and one for my display?


Joined Oct 26, 2011
yes you can ,if you wish you can use one battery for the 555/4017 side and the other to power yr display or if you wish use a 12v supply-build one or buy one to run the whole thing-post your schematic....

Thread Starter


Joined Nov 22, 2008
do I need a common ground for both power supplies? do I still use the same transistors or some other type of switch?


Joined Feb 19, 2009
The grounds need to be common, the transistors will perform the voltage transition.

Instead of 6V collector Voltage, use 12V collector voltage, such as two lantern batteries in series, but with the negative of the 12V tied to the negative of the 6V supply.

To oversimplify: Without the common, the transistor's emitter wouldn't be able to reference both voltages to switch or amplify.


Joined Jul 17, 2007
You said 31A's - I'm assuming you meant TIP31A transistors.

The 4017 wil not be able to source enough current for the TIP31A bases to sink more than about 150 ma current.

I suggest that you use logic-level N-ch MOSFETs instead of the TIP31A transistors.

If you don't want to do that, then you will need to something else to drive the TIP31's, like maybe 2N2222's wired as emitter followers.

I can't draw you a schematc for you, as I am on a "Web tv" kind of thng.. Perhaqps some other kind soul will.


Joined Jul 9, 2011
How much current DO you need for the loads?

Is the 3A max rating the TIPs have not enough or is the collector current you get from them not enough because the CMOS chip output current x DC current gain is too small? (as Wookie suggested)

Post a diagram and tell us how much output current you need.

Is it THIS circuit plus the TIPs at the output of the 4017?