Hi all,

I would like to ask the following, since it is the harder part for me to understand... I only have electronics as a hobby. I am doing a clock, and want it to be very precise, at many temperatures actually from -5c to +45c.

This is what I need to do:
Part A of project:
1 second timer circuit of which must use the TLC555IP
the output will be going to a 74ls192 decade counter.

What components would make very accurate 1sec pulse for the clock?
The place that I wil be buying my components (caps & resistors) from is Jaycar
Jaycar Electronics

They have MKT miniature Polyester, greencap polyester or mylar, Tag tantalum, ceramic, monolithic blue chip.
The TLC has different requirements than the normal 555 in the selection of components.

Part B of project:
somehow to use a 555 as a flip-flop so it can handle the multiplexing needed for some alpha numeric displays that I am expecting. how can it be used to be giving (or sinking in my case, since it is a common cathode) to be alternating the character.
here is a link for the segment display that I will be using.
Dual led alphanumeric display

or a very common multiplexer or a flip-flop ic commonly found would do too, but I have those handy(the 555's) same as the TLC, but the SA555 can source / sink 200mA but the TLC555 on the other can only do these:
* Sink 100 mA Typ
* Source 10 mA Typ.


Btw, I also have another timing circuit with a crystal (32.768Khz and a 4060...) but I really want to do it with the TLC555 since I want to make it "simpler" for me to do, since I would like to use what I have mostly at hand.

I also have a few '556's to use for the displays power. I think that will make it less 555's ;-)

Thank you to all that will help me.

 

Bad idea, keep the crystal and 4060 - they're much more accurate than a 555 who's frequency will drift all over the place.

If you want simple, then use a microcontroller rather than many ICs.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

Thanks, I know that, just wanted to try it out.

Any ideas on how I can be alternating the ground on/off between the various ground pins of the display so it would appear as it is always on? I think there was a way to do that with a 555 or a 556. That display is a 2 digit alphanumeric display, with each digit cut in half.

As for a microcontroller, I had only looked at the PIC series, but I don't have any of of the programming software and hardware, neither do I know programming, so I see that as a much harder option for me, since i don't want to copy 100% some one elses, but I want to do some of my own thing too. :-( besides, I wanted to be a little 'retro' I guess. I think of it as learning the building blocks before venturing out to the deep.

Attached Images

circuit-a.GIF (3.4 KB, 21 views)

 

You can use another crystal and an MM5369 as the oscillator.
I used the 555, a 4017 and four 4N25 optos in a name-in-lights project 20 years ago, later used as a Christmas light switcher, and it worked as cold as -45C ( windchill). Up to 100 bulbs were used.

 

Hi shokjok,
your project sounds great. Do you have any schematic of how you had done that part including the 555, 4017 & 4n25? Just asking since this sounds like something I will need for what I am planning.

Thank you.

 

Flashing Christmas tree lights don't need accurate timing so a 555 is ok. A clock needs accurate timing so a 555 won't do, use a crystal oscillator.

A one IC crystal oscillator is possible but the CD4521 and a 4194304Hz crystal are hard to get hold of these days.

__________________

I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

Hi Hero999,
Thank you for the image :-) I am able to obtain both of those parts ;-) plus the caps of which are 50v Ceramic, and resistors that are 5% carbon for the 4M7 1/4w and 2k2 in many variations ;-)
As for me asking for the lighting circuit, that was due to another part of the project.

It goes like this:
timing circuit, counter circuit, display circuit.
the 4n25 etc would be needed for the multiplexing part for the display. I will use 6 7 segment LED's and two alphanumeric LED's, that need multiplexing to display a word. So I would need to be alternating between between the two ground pins per character since it is dived in two.
As for the 1Hz signal, I was planning on using the 555 due to that I have a few of those, and wanted to test the concept before finalising it. I was going to use a breadboard to test the various parts before doing a board.

I hope that explains what I am trying to do.

if the multiplexing works, I might use the rest of the modules, depending how hard it will be

Here are the images for the part that will be showing the day of the week.



link to thread with info on these display's:
Dual led alphanumeric display

I might later try different alphanumeric displays in the future after about a month or so.

 

For alpha 14segment displays you're going to most likely need a microcontroller, or just treat them like seven segment displays.

__________________
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Smart Kits build Smart People
http://www.blueroomelectronics.com/

 

Hi guys,
Just wanted tp say thank you to all you guys that have helped me out. Also to a great guy too by the name of Rob Paisley.

I seen a circuit that I believed that would be perfect for the multiplexing part with a 555(556 actually), and asked him if he could assist me too.

So thank you so much guys for your assistance. Once USPS delivers the displays, I will take a couple of pictures to show how it will sort of look like :-D

So now I have sorted out the timer, the counters, the displays and the multiplexing :-)

Attached is the circuit that he helped me with.
His URL is the following:
LM555 Timer Circuits
It will take you directly to the circuit that had alarm bells ringing in my head as soon as I saw it ;-)

Attached Images

Display_Driver.GIF (5.3 KB, 20 views)

 

Hi guys,

Just wanted to say thanks to all.
My clock is progressing slowly but steadily, especially now that I have a lower back issue. For those that are interested, it is something called "L4/5 central spinal canal stenosis".

Anyway, I took a few pictures just earlier, when it was counting from 00-99 and then a short video after I added a 74ls08 AND gate to be resetting once it was reaching 60, actually only when it reaches 6 on the second '192. I am so proud of my self. I have about 30 minutes a week.

You can find further details in my blog over here:
Various writings, mumblings and dialogs.
It contains my thoughts about the circuit and how it is progressing.

So, for those that are interested, here are the pictures:

Attached Thumbnails

       

 

Good job aries but I find your blog difficult to read. I think you need to increase the size of your font and change it to a brighter colour like white or yellow so it stands out from the black background. (just my opinion)

 

Hi Colin,
Thank you for the feedback. I have changed the colour and also the font size. I guess it is due to that I like looking at smaller fonts so I can read more on a page :-) Just something I got use to the way I normally print. I also do two pages per side ;-)

Thank you for bringing it up. I have also changed the font colour too. It is a lime green colour.

Let me know if it is more enjoyable now.

 

Hi aries. That colour makes the blog much easier to read now IMO.