555 and ceramic caps

Can I use electrolytic capacitor instead of ceramic?
I have "tons and tons" of electrolytic but no ceramic ones (only the ones I received in starter kit) and I am trying to build 1KHz astable 555

This seems to be the easiest one:


The pin 5 to ground through (C2) 10nF - can I use a electrolytic capacitator here? How about C1? Is there an easier way to create 1KHz ?

(Trying to debug my oscilloscope why it's flickering :cold_sweat: )

BR,
newbie

That is for 1Hz
You will have to calculate for 1KHz
C1 can be electrolytic if need be.
C2 is there for stability, OK to not use it.

If you have an Arduino, do things in software.

.

Ceramic caps are very cheap... try eg ebay for mixed selections .

Allan#

No, large value ceramic capacitors are not good for timing because of the "voltage coefficient of capacitance".
Your 10uf X5R is not really 10uF. You will get a much smaller value.

Excellent article here:

allanhurst:
Ceramic caps are very cheap... try eg ebay for mixed selections .

Allan#

Already ordered! But takes a little time

LarryD:
That is for 1Hz
You will have to calculate for 1KHz
C1 can be electrolytic if need be.
C2 is there for stability, OK to not use it.

If you have an Arduino, do things in software.

.

Thanks, smallest I found was 0.10.1uF
Any idea how much this affects the hz?

Read the datasheet !

google NE555 and do the sums…

Allan

Dumb question, how do I know when the schematic's pinouts start to go to ground? Most of them are now in Vin

You have four connections to ground and only three to Vin.
Ground is that line at the bottom.

outro:
The pin 5 to ground through (C2) 10nF - can I use a electrolytic capacitator here?

So exactly how many 0.01uF electrolytic capacitors do you have there?

Grumpy_Mike:
You have four connections to ground and only three to Vin.
Ground is that line at the bottom.

Thank you so much. I got confused because the line is connected in bottom left!

If you want stable frequency C1 should be plastic film of some sort, ceramic and electrolytic are
not stable and ceramic isn't at all linear.

(This is for large value ceramic caps - the 1-200pF sort are stable but not large enough values for
low frequency oscillator)

Very confused.

So you need a 555 to oscillate at 1kHz? If the above circuit is correct and it oscillates around 1Hz, then simply dividing the capacitance by 1000 will get to 1kHz.

10nF = 0.01uF

Readily available in ceramic capacitors. Not the most stable in that range. As MarkT says, if stability is required, use a plastic film capacitor. AKA poly or mylar. They look like green chiclets or orange candy.

MarkT:
If you want stable frequency C1 should be plastic film of some sort, ceramic and electrolytic are
not stable and ceramic isn't at all linear.

(This is for large value ceramic caps - the 1-200pF sort are stable but not large enough values for
low frequency oscillator)

I believe there's multiple different construction techniques for ceramic capacitors. The large ones tend to be MLCC (multi-layer ceramic capacitor), not sure what technique the small values use. It's most likely the construction method that determines this, not the absolute value.

It is the type of ceramic used. The high dielectric constant stuff is not stable over temperature, voltage, or time.

The high value ceramic caps use ferroelectric materials like barium titanate which are not only non linear and
very temperature sensitive, they are microphonic (strongly piezo-electric). The dielectric constant of such materials
is measured in the 100's and 1000's

The low value ceramics are more normal ceramic materials with normal dlelectric constants, hence the
much smaller values of capacitance. For RF use frequency stability is critical and such ceramics can perform
extremely well: http://www.farnell.com/datasheets/1796416.pdf

There are 3-symbol codes for class of a ceramic capacitor like C0G and X7R, encoding temperature range and
stability with temp.

Can I use electrolytic capacitor instead of ceramic?

YES you can. If you do not need constant frequency values you can use any capacitor.
Some of the posts in this thead seem to have more a philosophical than a practical value.

For stable frequencies you should take another chip, not the 555.

I use a 100µF capacitore to generatie a 0.1 Hz signal with a NE555. It works well.

A crystal oscillator with a divider chain will give you a more stable frequency, but a 555 is good enough for many things and is simple.

Depends what yoiu need it for.

Allan

Thanks a lot everyone for your answers.
I came to ask quite simple question (with the wrong schematics :smiley: ) and I learned way more than I expected!

My main point was only to test what I can do and just mess around and try it with my oscilloscope.
One thing I noticed, that the oscilloscopes "signal" ( the green line ) is not as sharp as in in the "test" 1kHz signal which is integrated in the oscilloscope? Any thoughts?

And any thoughts on what should I do when I can't seem to get the signal sharp in general?

It's an analog trio (-77) oscilloscope