Circuit Problem!!!

[semajholland]

**broken link removed**

Can anyone tell me the matter with the circuit in the link above. I need it for a project that needs to be finished in 10 days and i'm starting to get desperate. Also there is an un-named transistor by the 555. Anyone suggest a suitable value????? Please help, thanks.

 

[HiTech]

The 555 is a timer IC chip not a transistor. However the transistor whose collector is tied to pin 2 of the chip isn't identified in that diagram.

 

[OutToLunch]

The unlabeled transistor is just a simple NPN - low current and the CE voltage will be low as well. The sole purpose of the transistor is hold pins 2 and 6 at a certain level to disable triggering in the 555. Use a 2N2222 or a 2N3904, etc.

As far as the circuit not working properly, I would suggest going through and debugging in steps. First make sure that the circuit is built properly - take your time and be anal. Have copies of datasheets at hand so you can look at pinouts, etc.

If it is still not operational after making sure it is wired properly, then start at the 555 timer and see if that is doing what is should be when eneabled (the output (pin 3) should be approx 1 sec pulses).

 

[oldtimer]

The 555 is an astable which pulses at a 1 second rate, the pulses are fed into the 4518 counter and when pin 7 goes low the relay is energised. The 4011 is a quad 2 input nand gate and is used to forwrd bias each diode or combination to display the pulse count..Any general purpose transistor will do in the 555 circuit.

 

[oldtimer]

You didn't say what wasn't working,does the display work? does the relay energise? check pin 7 on the counter does it go low,are there pulses on the counter clock pin.

 

[oldtimer]

Hitech,

I think you ought to take that silly comment out, it makes you out a moron.

 

[eng1]

The 555 timer is connected for astable operation. The 4510 is a BCD counter and the 4511 is a BCD to 7-segment decoder. After the 9th pulse the carry (pin 7 of the 4510) should switch the relay off. Try with one transistor that drives tha relay, with a base resistor. What's the problem exactly?
The unnamed transistor can be a bc547.

 

[semajholland]

I know a 555 IC isn't a transistor, i meant the transistor by the 555 chip. (Learn to read HiTech!!!!!) It's un-named. I wanted to know if i could put any old npn in it's place.

The display isn't lighting up and when i connect 12v across the circuit the relay automatically turns on straight away and doesn't do anything.

The output of the 555 is held high by the switch when it's off. But flick the switch and the out put goes low but stays low. No pulsing. I noticed the discharge wasn't connected into the circuit is this essential for correct operation.

All i want is a circuit that either counts down from 9 via a 7 segment display or by LED's turning off. Anyone have any circuit diagrams????

Great help, Thanks.

 

[Papabravo]

Hitech,

I think you ought to take that silly comment out, it makes you out a moron.

People are free to express themselves in any way they see fit. I think your comment makes you out a fascist, and a destroyer of our cherished liberties.

 

[Roff]

It sounds to me like your switch may be normally closed instead of normally open. Can you check it with a multimeter? You could also try holding the switch closed (open?) and see if it runs.

 

[eng1]

I noticed the discharge wasn't connected into the circuit is this essential for correct operation.

No, this is a minimum component astable multivibrator. It's ok.

Try to connect pin 4 of the 555 to 12 V. Don't connect the relay and check the output of the timer.

All i want is a circuit that either counts down from 9 via a 7 segment display or by LED's turning off. Anyone have any circuit diagrams????

This can be easily done with a microcontroller, can you use it?

EDIT: pin 7 of the 4510 is inverted?

 

[HiTech]

People are free to express themselves in any way they see fit. I think your comment makes you out a fascist, and a destroyer of our cherished liberties.

Thank you! It's amazing how many peeps there are on this globe who desire to squelch others. The right to free expression exists in America, but still has it boundaries as set by laws. Within Internet forums, for the most part, self-expression is bounded by the rules set forth by the administrator(s) or parent organization.
What some folks have failed to realize about my choice of sig lines is my sarcasm (however funny or not). My current sig line is non-threatening (in reality) and I don't plan to edit nor change it just because another member feels put out by it!

Now, having said all that, may I suggest that we keep this thread on topic?

 

[semajholland]

I think the problem could be the I.C's. Because i couldn't get hold of a CD4510and a CD4511. I had to substitute them for a BEF4516G and BEF4511B. I don't think these are doing their jobs the same. Does anyone know where i can get hold of these I.C's??

When i test the output of the timer, sometimes it pulses at 1 second intervals and sometimes it doesn't. Loose connection?

Can anyone come up with a circuit that counts down with L.E.D's instead of a 7 segment display?

Thanks.

 

[Hayato]

I think the problem could be the I.C's. Because i couldn't get hold of a CD4510and a CD4511. I had to substitute them for a BEF4516G and BEF4511B. I don't think these are doing their jobs the same. Does anyone know where i can get hold of these I.C's??

When i test the output of the timer, sometimes it pulses at 1 second intervals and sometimes it doesn't. Loose connection?

Can anyone come up with a circuit that counts down with L.E.D's instead of a 7 segment display?

Thanks.

Once upon a time, in a cars message board:
Well, I have a Mustang, nothing works there!
...After some time, after all the replies...
Well, I forgot to say that I could not afford a Mustang and I had to buy a Galaxie!

Well, from CD4511 to BEF4511B there is no difference.

But from CD4510 to 4516 there is a BIG difference, the 4510 is BCD, the 4516 is binary. So it will not drive your 7 segment display, unless you add a binary->BCD converter there.

The relay is not working, is it? Try to remove the 2N3053 (NPN, the one that is connected to the relay coil), the transistor pair there is not needed.

 

[Roff]

Once upon a time, in a cars message board:
Well, I have a Mustang, nothing works there!
...After some time, after all the replies...
Well, I forgot to say that I could not afford a Mustang and I had to buy a Galaxie!

Well, from CD4511 to BEF4511B there is no difference.

But from CD4510 to 4516 there is a BIG difference, the 4510 is BCD, the 4516 is binary. So it will not drive your 7 segment display, unless you add a binary->BCD converter there.

The relay is not working, is it? Try to remove the 2N3053 (NPN, the one that is connected to the relay coil), the transistor pair there is not needed.

Yeah, but for a single digit, BCD and binary are the same. The counter is being jammed to 9 when the switch is depressed, so either counter should work fine.
The 2N3053 is useful if you are driving a high-current relay coil (>100mA). Otherwise, as you say, you can remove it and ground the collector of the PNP.

 

[Hayato]

Yeah, but for a single digit, BCD and binary are the same. The counter is being jammed to 9 when the switch is depressed, so either counter should work fine.
The 2N3053 is useful if you are driving a high-current relay coil (>100mA). Otherwise, as you say, you can remove it and ground the collector of the PNP.

Yes, the transistor pair there (the PNP and NPN) is not needed, it's acting like a Darlington/Sziklai pair, I think that the high current gain is jamming the correct functioning.

I completely agree with you, about the single digit BCD and bnary.
But if you take a look in the CD4510/4516 datasheet, the IC's timing diagrams (page 5) are a little bit different:
https://focus.ti.com/lit/ds/symlink/cd4510b.pdf

 

[Roff]

Yes, the transistor pair there (the PNP and NPN) is not needed, it's acting like a Darlington/Sziklai pair, I think that the high current gain is jamming the correct functioning.

I completely agree with you, about the single digit BCD and bnary.
But if you take a look in the CD4510/4516 datasheet, the CI's timing diagrams (page 5) are a little bit different:
https://focus.ti.com/lit/ds/symlink/cd4510b.pdf

But CI* is not used (it's grounded).
How can high current gain jam the Sziklai follower?

 

[Hayato]

But CI* is not used (it's grounded).
How can high current gain jam the Sziklai follower?

Oops, I'm sorry, it's not CI it's IC.
CI = Circuito Integrado = Integrated Circuit (IC).

Well, The Sziklai follower has almost the same current gain of the Darlington pair, isn't it?
The 2N3906 beta is about 30 to 300.
The 2N3056 beta is about 50 to 250.
So we can have a beta of 1500, up to 75000. (if we get 2 good transistors with the higher beta).
If the circuit is very sensitive to very low currents variations, the relay will be activated with anything that is minimun. For example, the 555 IC reset pin current drain.

 

[Roff]

Oops, I'm sorry, it's not CI it's IC.
CI = Circuito Integrado = Integrated Circuit (IC).

Well, The Sziklai follower has almost the same current gain of the Darlington pair, isn't it?
The 2N3906 beta is about 30 to 300.
The 2N3056 beta is about 50 to 250.
So we can have a beta of 1500, up to 75000. (if we get 2 good transistors with the higher beta).
If the circuit is very sensitive to very low currents variations, the relay will be activated with anything that is minimun. For example, the 555 IC reset pin current drain.

The base of the 2N3906 is driven by the Carry Out pin of the counter. The Sziklai circuit is just a high gain emitter follower. High beta will not cause it to respond unpredictably, unless it happens to oscillate, which in my experience is only likely when both transistors have similar Ft's (transition frequencies).

 

[oldtimer]

People are free to express themselves in any way they see fit. I think your comment makes you out a fascist, and a destroyer of our cherished liberties.

They cetainly can,and do,but this is an electronics talk site.Get the idea.