TTL Clock with 7447 7490 and 7400 IC's

[krye]

Hi Krye,

I don't think I ever built a clock, that makes me the ideal
person to give you some advice on how to build one.

Connect all R9's to gnd, that will make the clock count
instead of displaying six nine's.

QD of U5 and CLKA of U6 are both connected to +5 volt, that's
probably a typo.

The setting for minutes and hours is completely wrong.

And . . . the hours counter will count from 0 to 13 ?????

As I said before, I don't know much about clocks so I could
be wrong.

on1aag.

You're right. It's wrong. It's all wrong! I don't know what I was thinking. I removed the schematic so I can redo it.

 

[mneary]

@krye: The flip flop should be set to toggle on the falling edge of the "1" driver.

 

[on1aag]

@krye: The flip flop should be set to toggle on the falling edge of the "1" driver.

Maybe like this ?

on1aag.

 

[mneary]

That's the basic idea.

 

[krye]

Hi Krye,

I don't think I ever built a clock, that makes me the ideal
person to give you some advice on how to build one.

Connect all R9's to gnd, that will make the clock count
instead of displaying six nine's.

QD of U5 and CLKA of U6 are both connected to +5 volt, that's
probably a typo.

The setting for minutes and hours is completely wrong.

And . . . the hours counter will count from 0 to 13 ?????

As I said before, I don't know much about clocks so I could
be wrong.

on1aag.

Cool, thanks

K

 

[FLores]

RODALCO PLS EMAIL ME THE SCHEMATIC DIARGRAM OF DIGITAL CLOCK WITH 555 TIMER pls. ..

sweet_ko2007@yahoo.com

 

[FLores]

I need the diagram of digital clock with 555 timer

Help me guys!!

 

[pao_wikhan]

im having problem with my clock hour simulation...my 12:00 time isnt goin back or rather resetting to 00:00...how am i goin to do so..im using ttl gates mainly 7490 & 7492 as seconds mins and hours...nid help..tnx

 

[sali147]

i have made a keypad 3*4 scanner and now i wanna to make a simple adder and mutiplier with keypad 4*4,anybody helps me?

 

[cacophony]

I have seen various threads with TTL requests regarding how to and build a TTL clock or counter with discrete components.

As I have build around 7 of these clocks in the early 1990's and these TTL, LED clocks are still going strong I decided to have a look in my archives and post the basic diagramme for it.

I have learned building them also by trial and error and from various sources like TTL Cookbook (Don Lancaster) and Digitale klokschakelingen (Herbert Bernstein) written in Dutch origin Germany.

As i like the old TTL technology and with carefull and accurate ratsnest wiring a very accurate clock can be build at very low cost but labour intensive but that doesn't matter for a hobby.

Important is the decoupling of every 74xx IC with a 100 nF disc capacitor.
I omitted these in my earlier clocks and later addition of these was painful but not impossible.

The numbers 6 and 9, can be made with tails by adding an extra 7408 AND gate to drive a BC 547 to sink the A and D segment when these have to light up.
A 74247 IC has those functions built in but i have never seen one of those.
IC's.

Attached is the basic schema which works well and i'm more than happy to give more info to potential TTL clock builders. Also i'm happy to post more photo's if required.

**broken link removed**

hm: :mu: hm:

Hi! Could you send me a copy of this schematic in a large-scale so I could clearly see the pins? I've built a schematic just this morning and ericgibbs told me that it might take a while to debug the errors. Could you also please point to me where the errors are? BTW, I've based my schematic on the attached file seen in one of the topics here about digital clock originally made by Sujoy Mukherjee et al.

Thanks!

 

[RODALCO]

TTL clock

cacophony

Attached schema is the only schema I have drawn up and works fine.

As long as the 100 nF decoupling capacitors are attached across the voltage terminals of the IC's it should work with no major problems.

My clock is now nearly 22 years old and happily ticking away in TTL technology.

 

[Lazze]

Hi guys !

I'm doing my first TTL clock and I'd be clad if someone could check my schematics briefly for any errors.

Thanks.

 

[audioguru]

Your 4521 is ordinary Cmos, not old TTL. So its max oscillator frequency is only 0.9MHz, not 4.2MHz when its supply is only 5V.
The output current of the 4521 oscillator is too low to drive the old fashioned TTL counters. Maybe a 74HC4521 will work.

When the switch is turned on then you have outputs shorted together. Which output will win?

 

[Lazze]

Audioguru, thank you for your tips. I'm a complete novice what comes to electronics but I'm eager to learn

Are you sure the 4521 can't handle that >4MHz frequency? I thought the limit was more around 6 MHz. You also said there wasn't enough current to so I put an Mosfet driving that first counter and couple of diodes to those minute and hour adjustment circuits. (btw, I made those switches debounced.) and now there are also switches for seconds reset and counter stop.

Any comments?

 

[audioguru]

Your Mosfet symbol is for a Jfet and does not show its drain or source pins. If its source is connected to ground then its drain is its inverted output but its drain is not connected to the counter IC. Instead, the counter's clock pin is wrongly connected to ground.

 

[Lazze]

Again thanks for clarifying things up.

I corrected the mosfet symbol, changed the output location and increased the gate-to-ground resistor to 100k.

How does this look like?

 

[mneary]

Your schematic shows a "4521N" which is the generic number, and the original ones were very slow on 5V. If you have a CD4521B, you would be lucky to get one MHz. If it's an HCF4521 from ST it might be good to 2MHz. Only newest ones (HEF4521) from NXP are guaranteed at the speeds you expect.

 

[global_wonda]

Hello everyone, am new here. I'v alwayz found this forum very interesting and educative. Pls, i want you guys to help me on HOW TO CONFIGURE A 74LS161 modulo 16 COUNTER TO WORK EXACTLY AS A 74LS160 MODULO 10 COUNTER.

 

[audioguru]

I was wondering why you use antique old TTL logic. Then I looked in Google to see that you are in Nigeria. Too bad.

 

[RODALCO]

7447 IC pin details

Hi, I'm not going to redraw the schematic as I haven't got the time for that.
I give you the pin details for the 7447 IC

PINS
1 BD
2 R0,1
3 R0,2
4 NC
5 Ub+
6 R9,1
7 R9,2
8 Qc
9 Qb
10 U- (neg)
11 Qd
12 Qa
13 NC
14 A