SC8560 AM/FM clock radio 50Hz drifts

[mvs sarma]

...................

Is 330 Ohm sufficient for R3 & R4 given that the supply is now rectified rather than half wave sine pulses?

Hi, the original value is already indicated by nura100 and the pulse seen by the display is square wave as compared to the half cycle sinewave. to that extent i had increased it value. let it start functioning we can reduce the current depending on brightness. now nura will comeforward to give a perhaps +ve compliance, and eager abt it, as we don't have a device to experiment. Manoj has either completed the project or on vacation for this redesign.


thanks & Reagrds

 

[ljcox]

A further thought.

I believe that the circuit sc8560modification.JPG that you posted can be simplified.

There appears to me no need for another supply voltage.

i already have used the method suggested by ljcox in his diagram, but it doesn't work, when the sources of both the Mosfets are connected to VDD, the display shows some weird symbols which are undesired.
nura

I think the problem of the "weird display" mentioned in the quote above is because the existing Vdd supply is half wave rectified, the Vdd supply rail cannot supply enough current during the half cycles when the diode is off.

Therefore, connect a diode from pin 3 of the transformer to Vdd so that Vdd is full wave rectified and should therefore have enough energy to supply the display. It may be necessary to increase the electrolytic (or connect another one in parallel) in order to cope with the display current.

 

[mvs sarma]

Hi
it will help isolate the display noise not to interfere with clock supply

regards

 

[nura100]

Hello Sarmaji & ljcox

YES! I DID IT,

thank you guys for taking time out to solve a problem started by someone(manoj) and continued by me.

it has a happy ending, after weeks of thought process and patientence.

i already had tried the circuits suggested by our beloved friends long back before this thread had started, but didn't work.

heres my final Working circuit diagram which is Accurate & ticks well!

 

[mvs sarma]

Hello Sarmaji & ljcox

.......................heres my final Working circuit diagram which is Accurate & ticks well!

Hi Arun,

CONGRATS

YOU TRY TO PUT THE ELEMENT OF MODIFICATION AS A JPG . LET US ALSO see and it might help many others.

NOW, THIS CLOCK CAN WORK FROM A DC source,and free from public mains.

Nice of you ARUN,

All the best to you--

Sarma
0 91 94401 54650

 

[nura100]

Thank You Sir,

here's my Ticking Version free from Erratic Mains Freq, Immune to Power cuts, accurate than those 32.768KHz digital Clocks.


i'll post my Project pics with all PCBS shortly, enjoy

Now i can have a goodnight's Sleep

Arun
from Hi-tech City (Sarmaji this clue is for you!)

 

[mvs sarma]

Hi Arun,
Did this clock work from LCD display?
if so why we are wasting power across 150Ohms to ground for cycle 1 and cycle 2?
did you dispense thre tranformer as it is not shown?
why not complete diagram?

 

[nura100]

Hello Sarmaji

yes i have dispensed Trafo for time being, My Clock runs on Battery which has a solar Panel attached for Charging during the Day!

No, LCD is just Pictorial, I couldn't get the image of a Duplex LED Display

You all Have Datasheets of LM8560,i assumed, so i drew the part of the circuit Diagram which was debated .

this Modification Does away with Trafo and can operate in Cars too, planning to have a "BLANK" switch when used in car to save battery drain!

bye
arun

 

[mvs sarma]

.................. i did search google for a standard 50Hz divider, but could not find any standard circuit... ....................i hope my thoughts are not too wierd !!

Hi Manoj

refer to your old post
here is a chip to get you 50Hz and 50Hz_ from 3.579545MHz

https://www.electro-tech-online.com/custompdfs/2006/12/ELM446DS.pdf

 

[ljcox]

Thank You Sir,

here's my Ticking Version free from Erratic Mains Freq, Immune to Power cuts, accurate than those 32.768KHz digital Clocks.


i'll post my Project pics with all PCBS shortly, enjoy

Now i can have a goodnight's Sleep

Arun
from Hi-tech City (Sarmaji this clue is for you!)

Could I suggest some simplifications.
Diodes D1 & D2 are not necessary since the CMOS is switching between Vss & Vdd AND are undesirable as they could cause thermal run away. When the transistors are off, the Icbo current should be shunted to Vdd so that it does not cause Iebo which can lead to thermal run away if the temperature is high.

If the display is an LED one, then you need resistors R5 & R6. And if these are not included then you don't need diodes D4 & D5. But your diagram indicates that it is an LCD one. So these components may be necessary (I would need to study the display data sheet to be sure)

In fact, I originally included these components in my diagram posted on 28 December. If you look carefully at the connections between Z1 & Cycle 1 and Z2 & cycle 2 you will see that they have been done in Powerpoint since I decided to remove these components after I scanned the hand drawing.

I now realise that the Zeners are not necessary. The brightness can be set simply by adjusting the resistor values.

 

[ljcox]

I searched for a data sheet for the LCD display H1331C but to no avail.

Do you have one? If not who is the manufacturer?

 

[nura100]

Hi ljcox,

may be you missed my last post where i had mentioned that i had used the LCD image b'coz i couldn't get the image of Duplex LED Display in my circuit layout software.


Regarding the IN4148 Diodes at the bases of Push Pull Transistors, i used them to protect my CD4013, when experimenting my first CD4013 smoked when one of the Transistors shorted, and let high current into one of Q-Q1 outputs.

so i used them as protection, many push-pull oscillator circuits have these switching diodes at their outputs. (except the ones with SG3525 IC)

by the way, i made the 4 Digit Duplex display myself using Flat/rectangular 5MM LEDs arranged in 7-segment Format.(very tiresome, even when i made own PCB)

i tried a lot to get 4 Digit Duplex Display in our martket, but everybody had 4 Digit Multiplexed ones, which doesn't work with this clock IC.

later i want to make BIG display using 87 to 103 LEDS(round ones) to be visible from 20-30 feet

WISH YOU ALL FOLKS OUTTHERE A VERY HAPPY NEW YEAR 2007 !

arun

 

[ljcox]

I did read your previous post but did not understand the point re the LCD display. Now I understand.

As I wrote, if it is a LED display then you don't need R5, R6, D4 & D5.

If you used Darlingtons for Q1 & Q2, you would not need diodes D1 and D2 since R3 & R4 could be higher (say 15 k) and thus protect the 4013.

 

[nura100]

Thanx Len

i copy that, mate !

arun

 

[manoj.patil.1974]

All,

Apologies for the late posts.. you all guessed it right !! I was on vacation and on the beaches.... did not have internet connection...

But I had decided to work on this design even on the beaches.... as per my last posts, I had theoretically found the issue and as the recent posts show, it was multiplexing the display by 60Hz but driving by a clock rate of 50Hz. So, the solution was simple. I used two SL100 to drive the display common nodes. Of course, the square wave was inverted using a BC547 transistor for one of the SL100's. And it worked !!! but I was on the beach so could not post my sucess... Today i was glad to find out that some one else has also tried this ... he appears from Hyderabad, India itself !!!! waav.... world is very smalll....
This concludes's this thread.. I am so happy to make this clock finally work !!!! I think this clock is worth $5 but i must have spent over $100 by now on the all the components and instrumentation... !! but i am still happy... this is a precious gift for me !!!!

Thanks a lot to everyone who has responded to my questions.... This is a wonderful forum !!!

 

[mvs sarma]

what about the experience you gained and it can not be valued in $$$

 

[nura100]

Hello Friends !

here are my Project Pics which i'd like to share with you all!

bye
Arun

 

[ljcox]

Very good Arun.

A question. How did you manage to compress the photos to 40 ~ 50 kb?

Photos from my digital camera are about 1.9 Mb and I don't know of any software that will compress them.

 

[Hero999]

He probably shrunk the pictures and used a lower resolution.

Great!

How long does that battery last for?

 

[Nigel Goodwin]

Very good Arun.

A question. How did you manage to compress the photos to 40 ~ 50 kb?

Photos from my digital camera are about 1.9 Mb and I don't know of any software that will compress them.

They aren't 'compressed' (apart from JPEG of course), they are just resized - making them smaller makes the file MUCH smaller.