Can a old-fashioned Germanium Diode be used with a 555 to drive a 4017, or drive a 4017 alone?

I was able to do it once before, and now, no matter what can not do it again.
What I got before was a nice, really slow, rather "random" triggering of the 4017.
But now, I can no longer seem o do it, and Ive backed myself into a corner, as Im supposed to recreate it again.
Thanks for any help you may have.
I have now attached the schematic. Diode used is an Oa7

 

Post a schematic, I got no idea where this fantasy diode of your is?

 

Post the circuit you used.
{Sensacell beat me to it}

 

Post a schematic, I got no idea where this fantasy diode of your is?

I have now attached the schematic. Diode used is an Oa7

 

I assume that you are trying to build a random noise generator.
There are random noise circuits using reversed biased PN junction devices. You will have to amplify the signal to make it trigger logic circuits.

 

I assume that you are trying to build a random noise generator.
There are random noise circuits using reversed biased PN junction devices. You will have to amplify the signal to make it trigger logic circuits.

View attachment 308290

View attachment 308291

View attachment 308292

View attachment 308294

WILL THIS DRIVE A 4017?? Thanks!

 

What does it take for a signal to drive a CMOS logic circuit?
Not much. All you need is the signal to exceed the lower and upper switching threshold voltages.

For CMOS gates, the threshold is just below and above Vdd/2.

 

Hi Kim,
What is pin #4 of the 555 connected too, your diagram does not show it??
E
It should be connected to pin #8, +6V

 

Hi Kim,
What is pin #4 of the 555 connected too, your diagram does not show it??
E

it seems to not be connected

 

You haven't got a charge resistor between pins 6/7, it should go across the diode!

 

You haven't got a charge resistor between pins 6/7, it should go across the diode!

so r2 should actually be across the diode, rather than in series to the diode??

 

Yes, but i would also put a 100 ohms resistor in series with the diode as well , because when the chip discharges the capacitor the voltage across it may blow the diode.

 

Hi Kim.
This is what LTspice shows with aGe diode, do you know the actual type?
E

2

2nD image shows pulse expanded.

 

Hi Kim.
This is what LTspice shows with aGe diode, do you know the actual type?
E
View attachment 308295

Its a oa7, but I have many different glass-type Germanium

 

hi Kim.
This is a OA91
E

 

hi Kim.
This is a OA91
E

Ok, please pardon my stupidity, but what does this tell me??

 

It tells you, if wired as shown and using a Ge diode it should work, the image shows the waveform

 

Its a oa7, but I have many different glass-type Germanium

Just add diode D2.

 

Looking at #13, it looks like the C2 charging current is the approx. 1.3 uA. This is a reasonable leakage current value for a germanium diode. I have one old datasheet that lists the 1N34 reverse current as "30 uA @ 10 V". Does it vary enough with temperature, etc. to be a source of randomness? Don't know, but probably not.

To the TS - what is it you are trying to achieve?

What is the goal for the overall circuit?

Do you think you need a random-frequency clock source?

If so, why?

ak

 

Can a old-fashioned Germanium Diode be used with a 555 to drive a 4017, or drive a 4017 alone?

The 4017 has restrictions on the characteristics of the clock signal. The signal must meet these restrictions to reliably trigger the 4017. Basically, the signal needs to be as "square" as possible with sharp edges. The 555 in your diagram conditions the randomized signal so it can reliable trigger the 4017 in a somewhat random fashion.