Building home-brew digital clock

[littletransistor]

Dudes,

I know this topic has been posted a million times, and also I have already know how to set up one, the only thing left are the chips which I'm going to order soon.

Basically, I want to run this clock on a +9V battery source, which is much easier for me.

However, the 74 series TTL is very picky as they only needed +5V and also voltage regulation.

So, if I have to use a battery, I have to change them all to CMOS, or just put a +5V voltage regulator for the 9V battery and then feed +5V to the 74 chips from it?

 

[MrDEB]

go with the cmos

lower power consumption and easier to work with as far as power supplies are concerned.
just be sure your grounded to prevent damaging the chips

 

[littletransistor]

lower power consumption and easier to work with as far as power supplies are concerned.
just be sure your grounded to prevent damaging the chips

I see. But I have troubles finding the CMOS equivalent of the 7805 and also the 7490. Right now I have the 4511 which is the display driver for the 7seg ones. Anyone knows of the subsitute?

 

[jbeng]

I would use the 4518 in place of the 7490 and a 4543 instead of the 4511. The 4518 is actually two BCD counters in one package and the 4543 lets you use a cc or ca LED display or an LCD. The type of display is determined by how the 4543 is connected. Some datasheet links:

4518 datasheet
4543 datasheet

Jeff

 

[littletransistor]

Thanks. What if I used the TTL, and use a 7805 voltage regulator and connect it to the 9V battery, will they work?

 

[audioguru]

A little 9V battery will not power an LED clock display for more than a few minutes unless the display is very dim.

A little 9V battery will not power a 5V regulator and many old fashioned TTL logic ICs for more than 1 hour.

But you can't see an LCD display in the dark unless it is lighted with LEDs that will quickly kill a battery.

Use a power supply and an LED display. The CD4511 has much more output current than the CD4543.

 

[littletransistor]

A little 9V battery will not power an LED clock display for more than a few minutes unless the display is very dim.

A little 9V battery will not power a 5V regulator and many old fashioned TTL logic ICs for more than 1 hour.

But you can't see an LCD display in the dark unless it is lighted with LEDs that will quickly kill a battery.

Use a power supply and an LED display. The CD4511 has much more output current than the CD4543.

Ok, guess I need that power supply in the long run. Heh heh!

So, is there any of those pre-made selectable voltage regulators sold anyway?

 

[ericgibbs]

Ok, guess I need that power supply in the long run. Heh heh!
So, is there any of those pre-made selectable voltage regulators sold anyway?

hi,
Wall plug mains adaptors are available in range of voltages and currents.
I would recommend you get a Vdc regulated adaptor.
Something from 9Vdc thru 12Vdc, 250/500mA, use a 7805 for the logic.

You could consider a small 9Vbty for the logic counting chain backup during mains outtages, just let the LED's go blank.

 

[audioguru]

Cmos ICs work when the supply voltage is anywhere from 3V to 18V and do not need a voltage regulator. Their current is almost zero.
Old fashioned and current-hungry TTL logic iCs need a regulated 5V at a fairly high current.

I use an unregulated 9VDC/500mA wall-wart adapter for Cmos projects. Its voltage is about 12V with a low load current and is 9V with 500mA.
i have an unregulated 9VDC/200mA wall-wart adapter that has an output of 22V when its load current is low and it gets very hot when its load current is 200mA.

 

[ericgibbs]

Cmos ICs work when the supply voltage is anywhere from 3V to 18V and do not need a voltage regulator. Their current is almost zero.
Old fashioned and current-hungry TTL logic iCs need a regulated 5V at a fairly high current.

I use an unregulated 9VDC/500mA wall-wart adapter for Cmos projects. Its voltage is about 12V with a low load current and is 9V with 500mA.
i have an unregulated 9VDC/200mA wall-wart adapter that has an output of 22V when its load current is low and it gets very hot when its load current is 200mA.

hi,
I agree, I would go for CMOS in a clock circuit with an LCD display, but IIRC the OP is commited to the 74 series and LED's.??

I would never buy or recommend an unregulated 'wall wart' psu.

 

[littletransistor]

Cmos ICs work when the supply voltage is anywhere from 3V to 18V and do not need a voltage regulator. Their current is almost zero.
Old fashioned and current-hungry TTL logic iCs need a regulated 5V at a fairly high current.

I use an unregulated 9VDC/500mA wall-wart adapter for Cmos projects. Its voltage is about 12V with a low load current and is 9V with 500mA.
i have an unregulated 9VDC/200mA wall-wart adapter that has an output of 22V when its load current is low and it gets very hot when its load current is 200mA.

hi,
I agree, I would go for CMOS in a clock circuit with an LCD display, but IIRC the OP is commited to the 74 series and LED's.??

I would never buy or recommend an unregulated 'wall wart' psu.

Yes, for now, I love to try the 74 series since they are widely available in my store.

Also, I found some regulated +5V AC-adapters. But how am I going to connect the thing to my breadboard? I don't think chopping off the jack will help and strip the end will just do righht?

 

[ericgibbs]

Yes, for now, I love to try the 74 series since they are widely available in my store.

Also, I found some regulated +5V AC-adapters. But how am I going to connect the thing to my breadboard? I don't think chopping off the jack will help and strip the end will just do righht?

If its a 2 pole circular connector, you can buy the matching socket and solder some wires to that.

IF you do strip the ends, take great care NOT to reverse the voltage to your board.

 

[MrDEB]

beware of wal wart units

some are built really cheap=no real filtration
in otherwords the voltage is not real clean
could cause circuit gremilins.
TTL are in need of a very well regulated and clean power supply.
several capacitors on the supply rails.
some plug n go supplies Ive seen are just a couple of resistors a transformer, couple of diodes and not much else.

 

[CCD]

u've gone so far, so design a little supply too. it's quite easy, for yr requirement, u'll need a small transformar (take 230v to 12v), put the diode bridge, have few large elctolyte caps followed by 7805 and finally decap.. there u go, with really a small size!!
otherwise, as u r already thinkin, buy easily available ac-dc adapter (12vdc o/p), put matching socket on yr PCB, follow the 12v i/p again with 7805 and decaps (0.01uF)!! I've tried this one in one of my circuits with TTLs, works great!!
--
https://dharmanitech.blogspot.com

 

[littletransistor]

Ok, so I found a 9V ac adaptor, but with the 600MA current. is the current too much for the TTL chips and the 78L05 regulator?

 

[Krumlink]

That is totally dependent on how many IC's, LED's, etc. For example my Binary clock can pull up to 750ma max at any one time.

 

[audioguru]

A power supply does not force its max current into a circuit.
The circuit draws as much current as it needs which might be almost nothing.

A car battery can supply hundreds of Amps. But only the starter motor in winter draws that much.

Simply add the current draw of each IC and the display. Then select a power supply with enough current plus a little more.
If you are rich then you could use a huge power suoply with a max current of way more than your circuit uses. The extra current simply will not be drawn.

 

[littletransistor]

Ok, I got the "second" part almost correct, but with some glitch. The 10s part is correct, it counted up to 9, but not the 0-5 part.

The modulo-6 one is having the problem, when the BCD LEDs I've set up doesn't seen to go up to 4. The LED won't lit up on the extreme MSB, and I can still see that it's counting up to 5 and reset to 0, like this:

000
001
010
011
000 <- ??? (should be 100)
001 <- ??? (should be 101)

000
001.. and so on...

I dunno what ever happened to the QC output...

edit: btw, my 74LS90s are Hitachi ones, and the A and the B inputs are reversed.

 

[davidbball13]

thats funny all of my 4000 series and 7400 series chips are made in Malaysia and you are from there

 

[futz]

Ok, guess I need that power supply in the long run. Heh heh!

Have a look at my **broken link removed**. It's powered by a 12V wall wart and has 9V battery backup. Might give you some ideas.

There's no reason it couldn't have an LED display instead of the LCD. A couple of **broken link removed** or similar would simplify the display wiring immensely, too.