LED Strips Display driven from 555 / 4017 counter

A 4093 (4 gates) or 40106 (6 gates) Schmitt nand gate can make a very simple oscillator with one resistor and one capacitor on each gate.
You need to know the voltage and current consumption of the LEDs before chosing the MOSFET.

 

If you can understand the 555 as an oscillator, then a Schmitt trigger oscillator will come as a pleasant surprise.
Put a resistor from output to input and a capacitor from input to ground. You will get an oscillator with equal on and off times, just the job for flashing LEDs. A 4093 gate has two inputs, these should be connected together.
The frequency f = 2.7/(RC) so 10μF and 270k will give 1Hz approximately.
Any unused gates should have their inputs connected to something, usually ground. The CMOS will supply very little current unlike the 555 but can drive a FET easily.

Using one output from a 4017 will give a 9:1 on of ratio but more than one output can be used.

I have the book 'CMOS Cook Book' by Don Lancaster (1977) but I do not know if it is still in print.

 

The inputs to CMOS have very high impedance so they will switch the gate from stray voltages in the vicinity. If the gate goes into fast oscillation, the gate will consume a lot of power and perhaps overheat.
Connecting the gate to something stops this wild behaviour.

If you use a 4093 gate driven from the oscillator, then you have two outputs to drive two LED strings, one being on when the other is off. The 40106 has six gates and could be used as an alternative to the 4093.
I often use the 4093 since I bought what I thought was one at a radio rally and I was handed a tube with well over a dozen in.

 

I know the 4093. The 4093 is a friend of mine. The 4093 is one of the all-time great CMOS parts, and I routinely suggest it as an alternative to the 555.

BUT - the circuit described in post #4, with a single resistor and capacitor forming a symmetrical square wave oscillator, can be done with a 555. The advantages are that a 555 has significantly more accurate transition levels, so the oscillator accuracy is much better, and it does not drift with temperature changes. The disadvantage is that there are no extra gates left over to do other things. If *all* you need is one oscillator, the 555 gets you there with the same parts count in an IC package that is half the size of a logic gate.

ak

 

Second that

 

The 555 and 4017 can run directly off the 12 V rail. Both chips can tolerate up to 18 V.

ak

 

Ok, so you cut 10 strips for the 4017?

Each 4017 pin out will require a mosfet capable of delivering the max load, use a multimeter and get the total current (in series) used per strip..

This will tell you the minum load and the cheapest mosfets to do the job, if the total load is under 500ma... i might even consider a cheaper power transistor over a fet...

(Eg tip31/npn or similar)

 

Not all TIP's are created equal. By datasheet, a 4017 will not saturate a TIP31 at Ic=500 mA. Real world parts, almost certainly. But there's not much margin for the base resistor value between undercurrenting the base and overcurrenting the 4017.

ak

 

Depends on the current draw... i guess if you wanted to save extra, buy 50 2n2222s for a dollar or so, then use the 2n2222 and TIP31 in a darlington pair configuration....

That's providing you need the extra current, i'm sure in the real world a 200ohm resistor from the 4017 out to the base of the TIP31 should do what you want...

Infact, when it cools down (38c in the kitchen, 110f or so? I have my setup in there) i'll try it myself...

What's the max current for 4017? I'll google it lol

 

http://www.ti.com/lit/ds/symlink/cd4017b.pdf

 

The LED strip is 99 cents on ebay !!!!!