A Pulse from a rising edge & a Counter issue

[haxxx]

1.)When my counter IC (4029)counts from zero to one pin 7 Goes high (7.5v)
I want to use that rising edge to pulse a second circuit. Any faster way to get a pulse other than using the 555, if not is it okay to invert that pin 7 output and go straight to pin 2 Of the 555.
2.) Also another little problem, A backward count from zero to nine also makes pin 7 go high. I understand y it happens based on the counters 4 outputs but is there any way around it, that is: “zero to one: yes” “zero to nine: no”.

Thanks,
Haxxx.

 

[Roff]

1.)When my counter IC (4029)counts from zero to one pin 7 Goes high (7.5v)
I want to use that rising edge to pulse a second circuit. Any faster way to get a pulse other than using the 555, if not is it okay to invert that pin 7 output and go straight to pin 2 Of the 555.

What kind of pulse do you want (voltage, current, width, polarity, etc.)?
Beware of using carry outputs to trigger a oneshot. Many counters have glitches on their carry outputs which can trigger the oneshot at the wrong time. You can generally solve this problem by gating the carry output with the clock.

2.) Also another little problem, A backward count from zero to nine also makes pin 7 go high. I understand y it happens based on the counters 4 outputs but is there any way around it, that is: “zero to one: yes” “zero to nine: no”.

Thanks,
Haxxx.

You can gate the carry output with the up/down control, so that it is only allowed to pass when you are in "up" mode.

 

[haxxx]

I need to trigger a relay for momentary on. 1 second pulse.
I don't mean to be a pain but
All my experience is from online reading.
I did already gate the clock and pin 7 Into a 4081(AND)
so my question is whether i can just invert that to a low to trigger a 555.
or whether the 555 is a must at all. If so, in the monostable circuit pin 2 on the 555 is normally held high by a resistor. How should i make my connection here.

Thanx.
Haxxx

 

[Roff]

I need to trigger a relay for momentary on. 1 second pulse.
I don't mean to be a pain but
All my experience is from online reading.
I did already gate the clock and pin 7 Into a 4081(AND)
so my question is whether i can just invert that to a low to trigger a 555.
or whether the 555 is a must at all. If so, in the monostable circuit pin 2 on the 555 is normally held high by a resistor. How should i make my connection here.

Thanx.
Haxxx

What is the clock frequency into your counter?

 

[haxxx]

I got a variable resistor on it and my led just blinks for a fraction of a second.
basically to debounce the counters clock, but the pulse width is flexible.
Oh by the way when i said any faster way to get a pulse i actually meant my labor not actually a faster pulse, sorry if there was any confusion.

Haxxx.

 

[Roff]

I got a variable resistor on it and my led just blinks for a fraction of a second.
basically to debounce the counters clock, but the pulse width is flexible.
Oh by the way when i said any faster way to get a pulse i actually meant my labor not actually a faster pulse, sorry if there was any confusion.

Haxxx.

I'm willing to help you with this, but I need to understand what you're trying to do.

Why do you have a counter?

Why do you have it count up or down?

What do you want the LED to do?

Can you post a schematic of what you have now?

 

[haxxx]

Basically i have this built so far all i need now is to be able to activate a relay on the count of one and a second relay when the count falls back to zero.
the led merely shows the timers pulse.

 

[Roff]

Basically i have this built so far all i need now is to be able to activate a relay on the count of one and a second relay when the count falls back to zero.
the led merely shows the timers pulse.

This is baffling. You started out by asking about getting a 1 second pulse from pin 7 on the 4029, and you don't even show pin 7 on your schematic. You talked about problems with counting down, but you have no control over up/down. You haven't answered most of my questions. Perhaps you think they are unimportant.
This is a moving target. I'm not offering any more advice until you can give us a coherent, well-thought out definition of what you are really trying to do.

 

[haxxx]

I apologize for any confusion.
The schematic I found online and did the necessary changes,
I've since gated the clock and the up/ down pin and switched to a normally closed trigger for the monostable. The circuit will be monitoring cars arrival and departure sounding an alert when the first one comes and when the last one leaves.
Again there was no deliberate aversion.

Haxxx

 

[Roff]

I apologize for any confusion.
The schematic I found online and did the necessary changes,

Yeah, that's what I thought. That's sorta like complaining that your fried chicken doesn't taste right, so we ask you to post your recipe, and you post the one for barbecue chicken that you found on the internet, which you modified but didn't tell us what changes you made.

I've since gated the clock and the up/ down pin and switched to a normally closed trigger for the monostable. The circuit will be monitoring cars arrival and departure sounding an alert when the first one comes and when the last one leaves.
Again there was no deliberate aversion.

Haxxx

Do you really want the counter to roll over to nine on the next down count after zero? Isn't that an error condition, indicating that the lot is "emptier than empty"? It seems like you need to do more than simply inhibit the pulse generated when the carry output ends.

 

[haxxx]

I hear u loud and clear.
A count of 10 will be sufficient for now. I've figured a way to stop it alarming when it gets to that zero after count 9. I'm using entry and exit sensors. Possible cascading later. any advice on the connection from the carry out to
pin 2 on the 555.

Thanks
Haxxx

 

[Roff]

I hear u loud and clear.
A count of 10 will be sufficient for now. I've figured a way to stop it alarming when it gets to that zero after count 9. I'm using entry and exit sensors. Possible cascading later. any advice on the connection from the carry out to
pin 2 on the 555.

Thanks
Haxxx

Here is a partial schematic showing how to deglitch the Carry Out, and also trigger a 555 when it goes back high.
When both Carry Out and CLK are low, the NOR gate output goes high. It will go back low when Carry Out goes back high (actually, CLK will go back high a few nanoseconds before Carry Out). When the NOR gate output goes low, the pulse is differentiated by the RC network and triggers the second 555, which I assume you know how to set up for a 1 second pulse.

 

[haxxx]

I'm grateful for everything. I'm a Screen printer/ machine embroiderer. Now online self-teaching "Electronics student". Reading learning daily.
I know the comparator at pin 2 in the 555 is looking for 1/3 vcc could u explain the theory of how U3 in ur diagram would recognise the NOR low output, while it is being held high. as well as what is happening at this connection when the cuircuit is at rest with carry out low and nor output high.

Thanx
Haxxx.

 

[Roff]

I'm grateful for everything. I'm a Screen printer/ machine embroiderer. Now online self-teaching "Electronics student". Reading learning daily.
I know the comparator at pin 2 in the 555 is looking for 1/3 vcc could u explain the theory of how U3 in ur diagram would recognise the NOR low output, while it is being held high. as well as what is happening at this connection when the cuircuit is at rest with carry out low and nor output high.

Thanx
Haxxx.

The capacitor blocks DC, so pin 2 on U3 is pulled to Vcc by the resistor. When the output of the NOR gate goes from Vcc to zero abruptly (when Carry Out terminates), the voltage across the capacitor can't change instantaneously, so pin 2 on U3 also gets pulled to zero volts, which is below 1/3 Vcc, so the U3 triggers. The capacitor then charges through the resistor until pin 2 again reaches Vcc. Pin 2 just has to get above Vcc/3 before the 555 oneshot times out, which it will easily do with the RC time constant I have chosen. This RC circuit is called a **broken link removed**.

 

[haxxx]

Again hats off, I'll post back on completion.

 

[haxxx]

I hadn't considered power failure
Would i have to backup the entire circuit so as not to lose count or is there a way to use a small battery to backup up the 4029.

Haxxx

 

[Roff]

I hadn't considered power failure
Would i have to backup the entire circuit so as not to lose count or is there a way to use a small battery to backup up the 4029.

Haxxx

Read through this parking lot counter thread. I brought up the power failure issue, and also suggested a more complicated counting scheme that doesn't have a problem with power failure.
I think you could use a backup battery. The only problem then is if your counter gets a glitch (not likely, but possible). From time zero, when you reset the counter, it never gets a real-time count of the spaces occupied (or available). If it misses one or gains one, it is wrong until you manually reset it.

 

[haxxx]

I think I may have figured out the counting part of the circuit. I'll post back as soon as i'm done, If i'm wrong i'll humbly apologize, I'm arranging so it counts a maximum ten then can only count down. also the audible alert now requires three different inputs based on the direction of the vehicle before it switches on. The counter is gated with the 555 pulse if still glitches i'm not sure there's anything more i could do, but to manually adjust it. May also put a capacitor across the 555 to help prevent a false trigger.

Thanks again,
Haxxx