Please help modified a circuit

[audioguru]

Your counter ICs are old fashioned TTL that need a 5V regulated supply and a 5V input signal. They will blow up with a 9V supply. They have a very low input resistance that stops your other circuit.

The CD4026 counter iC is new Cmos that works fine from a 9V battery. It has a very high input resistance that won't stop your other circuit. It counts when its input goes high so it needs a transistor as an inverter.

EDIT: The CD4026 uses a common-cathode 7-segment display.

 

[cannibal]

so I have to replace which IC with CD4026 counter iC ???

U1 or U2

and how the connections will be ???

 

[audioguru]

The 74LS90 is an old TTL counter IC.
The 74LS47 is an old TTL seven-segment display driver IC.
The CD4026 does both.

I was wrong before. The CD4026 can use its Clock Inhibit pin as a low-going counter input. Then a transistor inverter is not necessary.

Look at its datasheet to see how to connect it.

 

[ljcox]

Could you please show the connections in the diagram

I am getting confused

and what about the B1 which is 9V

That's why I suggested that you use a CMOS device.

The 4000 series CMOS can operate on a supply voltage between 3 and 15 Volt. So it will work quite happily from the same 9V battery as the 555.

Also, it uses much less energy than TTL, so your battery will last longer.

The data sheet shows how to connect the IC. I suggest you draw the full circuit and post it so we can check it for you.

 

[cannibal]

I suggest you draw the full circuit and post it so we can check it for you.

In progress

 

[cannibal]

Here it is

I tried to search for CD4026 IC but too bad I couldn't find it

need your comments

 

[ljcox]

What is the transmitter part? how does it relate the the rest?

Resistor R8 is wrong. The brightness of the display will change depending upon how many segments are lit.

Replace it with a short circuit and insert a 470 Ohm in series with each segment.

You also will need to insert 100 nF bypass capacitors. One between pins 5 & 10 of U1 and one between pins 1 & 4 of the 555.

Also, you are powering the 74LS ICs from the 4.5 Volt battery.

The manufacturers of 74LS series recommend that the supply voltge should be between 4.75 and 5.25 Volt. So your circuit will probably work when the battery is fresh, but it may become marginal as the battery ages. Why don't you supply it from the 5 Volt supply?

 

[cannibal]

I done what you said
please check and tell me if I done it right or wrong

the trasmitter will be 5 volt power supply with 2 laser pointers


about why I didn't want to use power supply with 5V in receiver is because the shap of the final device will not be near to the main supply

 

[audioguru]

The minimum supply voltage for an ordinary 555 is 4.5V. Your three alkaline battery cells start at 4.5V but quickly drop to 3.6V then the voltage drops slower down to 3.0V.

Your old TTL logic ICs need a regulated 5.0v supply to work properly.
Most ordinary 5V regulator ICs need a minimum input voltage of 7.5V.

 

[cannibal]

Ok now I will use 9V cell

and as 555 works fine with 9V

Could you please add in the image a regulated 5V before the TTL IC's to supply

 

[audioguru]

The voltage from a 9V battery is 9V when it is new but drops quickly to 7.2V when it is used. Then its voltage drops slower to 6V.
Most ordinary 5V regulators need a minimum input voltage of 7.5V.

A 9V alkaline battery will soon be dead when driving a voltage regulator and the high current of old TTL ICs and the segments of a 7-segment LED display.

If the 555 uses a 9V supply and drives the old TTL IC then a voltage divider is needed so the 9V doesn't destroy the TTL IC.

That is why we said to use a CD4026 IC that has an extremely low supply current and works without a regulated supply.

 

[cannibal]

I searched for CD4026 but I couldn't find it
may be it's not available in my country

in the some time I don't want to use fixed voltage power supply from the main supply

could you please tell me how can I make a 5 volts reach the TTL while I am using the 9V battery

by the way this will be only for showing and testing several times not for daily use, that’s why I don't bother if the 9V battery will die

 

[ljcox]

I done what you said
please check and tell me if I done it right or wrong

the trasmitter will be 5 volt power supply with 2 laser pointers


about why I didn't want to use power supply with 5V in receiver is because the shap of the final device will not be near to the main supply

You should have used a ceramic capacitor for C4, not an electrolytic.

Electrolytics have too much impedence to be of any use as a bypass.

 

[cannibal]

and what about C3 ??
and how can I make a 5 volts reach the TTL while I am using the 9V battery ?

 

[audioguru]

and what about C3 ??
and how can I make a 5 volts reach the TTL while I am using the 9V battery ?

Use a low-dropout 5V regulator for the TTL and the 555. If you can't find a low-dropout regulator then use an ordinary 7805 and replace the battery when the circuit doesn't work anymore.

 

[ljcox]

and what about C3 ??
and how can I make a 5 volts reach the TTL while I am using the 9V battery ?

Sorry, I forgot C3. Yes, it should be a ceramic also.

I agree with Audio re the 5 Volt supply.

 

[cannibal]

Could you please see if what I did is right or wrong ?
and do I have to add something where red question mark is

 

[audioguru]

Look at the datasheet for a uA7805 regulator. They recommend using a 0.33uF input capacitor. Yours on the receiver has nothing.

Look at the datasheet for any old TTL IC. The absolute max input voltage allowed is 7V. Your circuit feeds it 9V.

Insted of using a voltage divider on the input to the old TTL IC then power the entire receiver circuit from the regulated 5V supply.

 

[cannibal]

Hi again

please check this attachment


and C5 is electro or ceramic ? its not clear in the datasheet

 

[audioguru]

A ceramic capacitor is a low impedance up to a very high frequency.

An electrolytic capacitor is wound around and around like an inductor at high frequencies.

Some film capacitors are also wound around and around like an inductor.

An inductor is a high impedance at high frequencies.
You want a low impedance at high frequencies at the input and output of a voltage regulator.