audioguru

The 4011 has a 15V supply. Its minimum input-high voltage is 11V. Some might work with an input high voltage of 7.5V.

But the 555 has a supply voltage of much less than 9.1V. So its output high voltage is less than 7.8V and most 4011 ICs won't work.

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Uncle $crooge

mvs sarma

Generally high and low voltage sensing is done before filter(C1). Both these signals could be ANDed and drive a single transistor. the so called delay created by the timer cold be also created by RC network (R in series and C in parallel after R).If timer is used, perhaps timer and cmos IC can both have same voltage, say 9V. you may also see the recent comments of Audioguru, in this context. Finally nothing should prevent operating the buzzer from operating from the same voltage even.

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Regards,
Sarma.

ericgibbs

hi sarma,
As I have posted, the design needs a lot of reworking, do you want to volunteer..

Regards

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Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

kris1

If we give the Sensed voltages to the same NAND gate or and gate. as two inputs, we get 1 0 ---->1
0 1 ----->1
0 0------>1
1 1------>0
That means it can sense only one abnormal condition but not both.

As you said same supply for 4011 and timer. The timer will not get supply as long as relay is energised.
As u said i also feel that we can have a simple RC instead of TIMER.
But it need to be discharge soon after switching on of relay.
Then only we can have protection from sudden tripping and resumption.

mvs sarma

Eric, As you are already on the process i would like Kris1 to make it work and learn from the design.
I would, in the mean time try and come out with a so called v.2. Perhaps it is more important that Kris1 should apply himself and learn to improve the design.

__________________
Regards,
Sarma.

ericgibbs

hi Sarma,

The problem there are so many things wrong with the design that it would be easier to start again.

Basically all Kris is trying to do is detect a min/max voltage and operate a relay and a buzzer with a start up delay.

It would be easier to design a new circuit from scratch, rather than keep on modifying his present design.

I agree an OP should always try to come up with his own design and post it for comment, I applaud him for doing that.

'Agu' has also pointed out some serious shortcomings in the design, as have other members.

At some point we have to say to the OP, go back to the drawing board.

Regards

Kris:
I would suggest you make on a project board, the individual sections of the design and test them out one at a time, use a variable bench power supply in place of the mains connection.

Try out the min/max 4011 detection part first.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

mvs sarma

Thanks Eric,
In fact this is an element used in Voltage stabilizers, in India, but, the low and high detection is better done using LM324 with preset reference inputs and sense voltages using a pot as used by Kris1.

I wonder whether we can use the trigger and threshold pins of the timer independently. (i mean use it as a single comparator).

BTW, on the way Kris1 designed, he could perhaps use more gating logic and finally drive a single transistor driving a relay.

AG's comments are just Nice.

perhaps the 4011 can be operated at 5V Vcc and the potentiometers so adjusted to meet the needs. The 555 output can be level shifted to match 4011 input. The output of gate(with Pins 1,2&3) can be inverted by the 4th spare gate and used as input at pin5. and finally have only Q2 driving the relay. ... I have to think of refining the present circuit even. All floating concepts.I shall come out shortly with a reasonable logic.

__________________
Regards,
Sarma.