LED Candle, help! Does this circuit work?

[HarveyH42]

First, I didn't design this circuit.
Second, I used 4011 NAND gates insted of 4093 (what I had)...

I simulated this with Livewire, works. And then built it on a proto board, which doesn't. The LED stays on, no flicker or fade. Hooked up my cheap hand-held scope, each gate seems to oscilate, but not all together, or at the LED. Perhaps I need to isolate the NAND outputs with diodes (1N914).

 

[jbeng]

Any idea as to what R9 is supposed to be doing for the circuit? Seems to me that it's just wasting ~9ma of battery current.
JB

 

[eblc1388]

First, I didn't design this circuit.
Second, I used 4011 NAND gates insted of 4093 (what I had)...

Course you don't. Ever wonders why a "schmitt trigger input" 4093 is used instead of 4011?

 

[audioguru]

Schmitt Trigger oscillators don't work without having gates or inverters with Schmitt Trigger inputs.

The oscillators will all operate at different frequencies and their outputs add and subtract which randomly brightens and dims the LED.

 

[HarveyH42]

Thanks. I could have sworn I've seen a 4011 used as a clock for something. I generally stick with what I know, 555 based astables. I'll look for some 4093s next time I surplus shop. I've got some 40106 inverters coming soon, maybe I can rework this some...

 

[audioguru]

Thanks. I could have sworn I've seen a 4011 used as a clock for something.

Yes, an ordinary Cmos inverter or gate is an oscillator if two of them are used like this:

 

[ljcox]

The 40106 is a hex Schmitt and will work in this circuit. But connect the inputs of the 2 unused inverters to gnd.

Schmitt Triggers provide hystersis which is necessary for the oscillator function.

I suggest you replace the energy wasting R9 with a 100 nF capacitor to provide some bypassing.

You don't need the 2 inverter oscillator, the single inverter one works well.

 

[wolfyeb]

2 questions!

a) Is there a way to make this circuit run off a 12v current

b) is there a way to get it to drive multiple LEDs... say 5? or possably an array like

 

[Hayato]

Harvey. Use the logic gates to sink current, not source.

 

[audioguru]

Harvey. Use the logic gates to sink current, not source.

No.
Look at the datasheet for any buffered ordinary Cmos gate or inverter. They source almost the same amount of current as they sink because they are symmetrical.

 

[Hayato]

Indeed. I forgot we were talking about CMOS.

 

[kchriste]

We are also talking about a thread from 2006!

 

[mvs sarma]

you may try using CD4093 instead of CD4011
The pin outs are same, as I remember. It should work.

 

[Hayato]

We are also talking about a thread from 2006!

Oh My... Looks like we have some grave violators over there.

 

[audioguru]

Its nice to have an LED that flickers like a candle. It doesn't matter that it is almost 4 years old.

 

[HarveyH42]

Wow, didn't even remember posting this one. It's from before I started using microcontrollers, did it with an 8 pin AVR for under $1.00 ... I've got several boxes of 74xx and 40xx chips, that likely will never get used, but who knows. Most were pulled from sockets, and should be good.

Anyway, kind of like seeing people pull up old threads, better than the same questions being asked over and over. With all the flame-less candles on the market, surprised that there aren't LEDs with built in flicker circuits. They blink, they fade RGB, why not flicker?

 

[kchriste]

I always preferred the the look of **broken link removed** over LEDs. But if it is hidden in a pumpkin and needs to be battery powered, the LED technique wins the prize.

 

[audioguru]

About 48 years ago I made neon bulb Chasers that were powered from two 45V batteries in series. Then I cast them in clear solid plastic.
They blinked for 6 months then blew up because the batteries were sealed in the plastic and the gasses could not vent out.