7555 pulsating led

[MrDEB]

designing a Statue of Liberty lapel pin for the 4th of July 2023'
have two similar schematics for a pulsating led (white 3mm led) but the capacitors are electrolytic caps that are larger than 3mm in diameter (have only 1/4 inch height restriction. THINKING of maybe using a titanium cap or? need to order parts but the capacitor size?
both of the schematics are basically the same.

 

[Pommie]

Resorted to shouting now eh. Can you not post an example? Why must I follow links? Is it so complex that posting examples is difficult?

Post an example. Note, no shouting involved.

Mike.

 

[danadak]

Have a nice day.

 

[Pommie]

So, no example then. Oh well.

Mike.

 

[danadak]

links take you to examples

do you want files, go to respective block language site and download their
examples, or to their user groups.

or duplicate the screen shot block examples in the links i posted for you and forum to click on.

 

[MrDEB]

the Tayda flashing LEDs are 5mm at 1.5hz (90-96 per minute)
going to experiment with the LEDs in series (flashing(5mm) and white 3mm LEDs.
I might get away with just 1-2032 coin cell battery.
just blackout the flickering LED with tape or?

 

[danadak]

< 2 Hz will satisfy :

https://www.epilepsy.com/what-is-epilepsy/seizure-triggers/photosensitivity

Only question is this part good over T and V to stay around 1.5 Hz or do you need
more margin.

Epileptic population estimated at 1.2 Million in US so this consideration should be handled.....

just blackout the flickering LED with tape or?

What is this consideration for ?


Regards, Dana.

 

[Pommie]

links take you to examples

do you want files, go to respective block language site and download their
examples, or to their user groups.

or duplicate the screen shot block examples in the links i posted for you and forum to click on.

You push this nonsense all the time. If I learn a language, Spanish, c, python, whatever. I know that language. If I go with your block stuff then I learn how to use that software, not a language. Bit like learning how to use Word or Photoshop. Exactly why you can't post an example. Or can you?

Mike.

 

[danadak]

218,000,000+ hits on Google, not just me discussing this. For Scratch alone I got 35,000,000 hits,
how about you, you doing some searches to educate yourself ? S4A I got 500,000 hits, 2,700,000+
for flowcode.....and the beat goes on.....

OMG just found Microsoft in the hunt https://www.microsoft.com/en-us/makecode

MIT and Google and Berkeley and.....all working in this area, guess they are pushing this

links take you to examples

do you want files, go to respective block language site and download their
examples, or to their user groups.

or duplicate the screen shot block examples in the links i posted for you and forum to click on.

 

[Pommie]

Can you post an example yet?

Mike.

 

[AnalogKid]

One like this will work.

Great find! RCA had some signal transistor arrays back in the 60's and 70's, and I've used Motorola quad 3904's, but somehow I missed this one.

ak

 

[Tony Stewart]

Ceramic caps will work fine here. But a coin cell is inadequate and adds a few hundred ohms. So your requirements are unclear. But using Schmitt 74LVC14 's are the simplest solution.

https://tinyurl.com/2jzty2p4

 

[MrDEB]

that looks tooo simple. will look ito it for the reindeer project

 

[AnalogKid]

that looks tooo simple. will look ito it for the reindeer project

Belieeeeve it. Some logic gates have Schmitt Trigger inputs, which makes things very simple (though not super-stable). The technique was first published in 1936. Schmitt was studying the nervous system of a squid.

A 555 with reasonably decent parts around it will have better frequency stability, and the actual frequency will be closer to the calculated value. The issue with Schmitt Trigger gates is that the two transition voltage levels are not tightly controlled in production. This means tha for a given set of R and C, the actual frequency can vary with temperature, and from one chip to another. Nothing huge, maybe +/-10%, but a 555 comes in at around 2% (working from memory).

I like ST oscillators. I'm not a huge 555 fan, plus I often work with circuits that already need logic gates for other stuff. If there really is no need for the other gates in a package, then an 8-pin 555 is smaller than a 14-pin hex inverter of quad-NAND.

For really small size, Micrel(?) makes 555 derivatives that are missing a few pins. One is optimized for a monostable, and one is optimized for an oscillator. I think they are in a SOT-5 or -6 package.

For even smaller size, people make tiny CMOS logic components that have only one gate or inverter per package.

https://www.diodes.com/assets/Datasheets/74LVC1G14.pdf

https://www.digikey.com/en/products/filter/gates-and-inverters/705?s=N4IgjCBcoKxaBjKAzAhgGwM4FMA0IB7KAbRABYAGCgZgHYKR9KaA2ADkfKrogF18ADgBcoIAMpCATgEsAdgHMQAX3xgW8EEkhoseQiRAAmMgE4wMOPxDDREmQuX4WJjVp058RSKUonqfkCsbSHEpOUUVIzJaVxQMD31vEGoYE1paDiCRELtwxxBUw1jteL0vUjA2NhgKTMFs0PsI1RM2F2hNON1PAwZeSIBaIo6tKQBXMoNLJUj1DukAE1EBsAoIetFOIQBPAWxRVEwkGaA

ak

 

[danadak]

Can you post an example yet?

Mike.

prior links in multiple posts take you to examples

do you want files, go to respective block language site and download their
examples, or to their user groups.

or duplicate the screen shot block examples in the links i posted for you and forum to click on.

 

[MrDEB]

will consider the 74LVC1G14
It looks too simple but if it works.
curious What simulator is Tony Stewart using?

 

[danadak]

Circuit Simulator Applet

Regards, Dana.

 

[danadak]

As tempting as the Schmidt is it has very large V and I suspect T
device to device variation. If this is a one off no problem. But for
a design with relatively accurate pulse rate.....doe not look good :

Look at Hysteresis values all over 2:1 kinds of variation. (at 1 specific power supply value), its ~4:1
over Vcc variation. Then throw in T variation on top of that.

Not only that we have problem with input leakage, creating huge offset thru 10M R......, the large R
used to facilitate small cap use. So to mitigate we need much smaller R, hence larger cap, meaning we
get large cap pile on T errors.

Regards, Dana.

 

[tumbleweed]

This is for a blinky led, so I doubt accuracy matters much

 

[AnalogKid]

As tempting as the Schmidt is it has very large V and I suspect T
device to device variation.

My guess was +/-10%. Picking a set of values from the chart you posted comes in at +11% / -12% worst case, with no typical value given.

To evaluate this information in the context of this application, consult the Index Of Good-Enoughness.

ak

 

[danadak]

My guess was +/-10%. Picking a set of values from the chart you posted comes in at +11% / -12% worst case, with no typical value given.

To evaluate this information in the context of this application, consult the Index Of Good-Enoughness.

ak

And thats not including passive T effects.....and if you back into the trip levels worst case for the
min/max trip levels from hysteresis (crude approach) I think you are looking at 50% or more.
I looked for a good spice model for Schmidt, no luck so far, to run some monte carlo sims over
T and V to confirm my suspicions. Maybe just a quick heat gun and power supply test would
suffice.

The above came from me looking at a different vendor who did not spec the actual min / max trip
levels, just the min max hysteresis.


Regards, Dana.