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.
I believe that the circuit sc8560modification.JPG that you posted can be simplified.
There appears to me no need for another supply voltage.
nura100 said:
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.
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?
.................. i did search google for a standard 50Hz divider, but could not find any standard circuit... ....................i hope my thoughts are not too wierd !!
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.
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 !
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 !!!