Need an expert's suggestion.

[simo_x]

Hi all, I am working on a little circuit that it count from 1 (showing it when turned on) to 6 when button switch is pressed.

I have used an RC of 100K and 100n to give a PGT to Master reset, from 0 to 1.
Another RC of 10K and 10uF is used to give a PGT to the clock passing through a transistor Q1.
The signal from the switch pass through Q2, and the R15 is needed to limit the returning 0V from Q2 to Q1's emitter.

My doubt is: as I still don't have very strong knowledge about transistors, I am not sure this circuit will correctly work, however in the simulator seems all ok, but obviously I don't trust at all.

What do you think about it? I appreciate your suggestions.
Thank you for your interest.

 

[ericgibbs]

Hi all, I am working on a little circuit that it count from 1 (showing it when turned on) to 6 when button switch is pressed.

I have used an RC of 100K and 100n to give a PGT to Master reset, from 0 to 1.
Another RC of 10K and 10uF is used to give a PGT to the clock passing through a transistor Q1.
The signal from the switch pass through Q2, and the R15 is needed to limit the returning 0V from Q2 to Q1's emitter.

My doubt is: as I still don't have very strong knowledge about transistors, I am not sure this circuit will correctly work, however in the simulator seems all ok, but obviously I don't trust at all.

What do you think about it? I appreciate your suggestions.
Thank you for your interest.

hi,
It looks OK, but the circuit is over complicated.
As you are using the PLd to set the count to '1' after the '6' I would have used that line to initialise to a '1' at power up rather than pulse the clock.
That would remove the need for the two transistors.

Whats the NAND gate circuit connected to the 4511 doing.???

 

[simo_x]

hi,
It looks OK, but the circuit is over complicated.

Thank you for your answer.

Whats the NAND gate circuit connected to the 4511 doing.???

When the number 6 is showed to the display, segment a will be turned off.. As I use a NAND gate to load the preselect pin, I use the rest of the gates to turn on segment a when number 6 is showed. Also, I prefear it on..

Two last questions.. What are the correct R values to connect at the base of BC548?? I unsure about it but I am thinking about 10K..
Also, I am thinking to substitute R15 with a diode to prevent the returning 0 V to Q1 emitter.. Should be better, right?

Again, thank you for your reply.