555 Timer Circuit Short pulse Help

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
No, pin 8 is positive supply, pin 4 goes to to the resistor and capacitor like in post #66,
Use a 1 mega ohm resistor and 1micro farad capacitor and the power up delay will be Approx 1second, if its not long enough use a 2.2 microfarads.
Ahhh, OK I think I know what was going on.
OK if I wait a little while I guess the capacitor drains and I plug in my power supply and it does not send a pulse, if I unplug my power supply and then plug it in again quickly then it does send a pulse.

:)
 

Dodgydave

Joined Jun 22, 2012
8,589
Ok,when the rockers are pressed do they need to send a pulse to a different dtmf chip via the timer,

Do you want each rocker switch to sends a pulse to its own dtmf chip,?
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
Ok,when the rockers are pressed do they need to send a pulse to a different dtmf chip via the timer,?
Nope, luckily the DTMF random tone generator of the voice box simply makes a connection to ground normally via a momentary switch, hence the need for the momentary pulse ;)
What I do is pass ground pulses from buttons into a series of diodes set up as a "Multiple IN - single Output" type of scenario. Like thisSpaceMattButtonsWiringWithDiodes_LR.jpg
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
DTMF_PulseForDPDT_Rockers_LR.jpg
Ok so where does the pulse go to then, as its not on your circuit?
Check out post 84, The DTMF is in the voice box. It just needs a negative pulse, Basically from our timer circuit I'll take the positive output from pin 3 of the timer IC and run that into an optocoupler through a 470R resistor, the switch of the Optocoupler will send the negative pulse to the DTMF tone generator in the VB through that multiple in single out rectifier diode scenario.

Here is the 555 timer circuit with the Optocoupler attached.
 
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ScottWang

Joined Aug 23, 2012
6,843
*-
Ahhh, OK I think I know what was going on.
-
OK if I wait a little while I guess the capacitor drains and I plug in my power supply and it does not send a pulse, if I unplug my power supply and then plug it in again quickly then it does send a pulse.

:)
If this is happened in the 555 parts then it was not discharge completely, you may try adding a discharge resistor in parallel with 12V and GND, the discharge current from 1~10mA and the R values from 12K~1.2K.

I assuming that was bjt stage caused that, so the pin 2 adding an in4148 in parallel with 100K(Pin 2 to 12V) and the "-" of 1N4148 connecting to 12V.
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
*-
If this is happened in the 555 parts then it was not discharge completely, you may try adding a discharge resistor in parallel with 12V and GND, the discharge current from 1~10mA and the R values from 12K~1.2K.

I assuming that was bjt stage caused that, so the pin 2 adding an in4148 in parallel with 100K(Pin 2 to 12V) and the "-" of 1N4148 connecting to 12V.
Sounds cool, could you diagram that out for me just so I'm clear on it. Also does the Diode have to be IN4148 or can it be another value like IN4007?
You know I always thought they were called 1N4007 (1 instead of I) lol Still learning so much of this stuff.
The various types of transistor pinouts drive me pretty batty too lol
BTW what is "bjt"?
 
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Thread Starter

Michael Knight

Joined Nov 5, 2015
90
Mike , if your dtmf chip needs a negative pulse, why the bother of using a 555 timer and inverting it with an opto,..is the dtm working on a different supply?

You can use a CD4538 dual monostable, it has either positive or negative triggered inputs, and both positive and negative output pulses...

http://schematics.dapj.com/2004/11/monostable-multivibrator.html?m=1
Well soak me in pig drippings and spank me silly :)
I never knew such a thing even existed.... lol like I say I'm very new to a lot of electronics, I have a very basic knowledge at best, but I can follow a diagram and even make some simple tweaks if I comprehend it well enough, lol been doing a lot of that on this project ;)

Yeah the Voice box in the Knight Rider electronics is run on 12V, I did fry the random DTMF chip one by hooking it up wrong and had to get a replacement chip sent out from Knight Rider World, since then I have taken to isolating the pulses going to it through an optocoupler as it totally ensures that I don't do that again ;)

Soooo.... how does this other funky chip work?

The only chips I have gotten in my collection since getting into all of this a fair amount are:
CD4060BE (I had bought this one for a police lights flasher circuit I wanted to try out)
CD4017BE (Which I have been experimenting with chaser circuits with)
CD4049BE (And I can't for the life of me remember why I ordered that one lol)
 

ScottWang

Joined Aug 23, 2012
6,843
Sounds cool, could you diagram that out for me just so I'm clear on it. Also does the Diode have to be IN4148 or can it be another value like IN4007?
You know I always thought they were called 1N4007 (1 instead of I) lol Still learning so much of this stuff.
The various types of transistor pinouts drive me pretty batty too lol
Using 1N4148 for quick speed, light current, using 1N4007 for high voltage, if you want to using 1N4007 to replace 1N14148, I think it's ok here, please check D6 and R9, maybe you can using one 2K + VR10K to replace R9, and to testing the discharging time.

I only using one 1N4007 to replace 1N4001~4007, because they look almost the same, so I decided to use the same number.
DTMF_PulseForDPDT_Rockers_LR_ScottWang.gif
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
Using 1N4148 for quick speed, light current, using 1N4007 for high voltage, if you want to using 1N4007 to replace 1N14148, I think it's ok here, please check D6 and R9, maybe you can using one 2K + VR10K to replace R9, and to testing the discharging time.

I only using one 1N4007 to replace 1N4001~4007, because they look almost the same, so I decided to use the same number.
View attachment 94398
OK thanks ScottWang,
I'll give this a shot, the amount of discharge time is not totally important as it seems that when I unplug the power supply, if it is off for (and I'm guessing here) maybe a 5 or 6 second count that is more than enough time for practical day to day usage, as the ignition would be off, and by the time you started the car and started pressing buttons from the last shut off time the chip or caps should have had plenty of time to be discharged... again just guessing based on plugging it in and unplugging it.But hey if this does it faster and ensures the discharge time is faster I'm all over that my friend ;)

Oh is there much difference between those Diodes, I see in a lot of 12V circuits that they seem to hover around those number ranges, so I had bought a bunch of different kinds in that range because I see them used a lot.?
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
Using 1N4148 for quick speed, light current, using 1N4007 for high voltage, if you want to using 1N4007 to replace 1N14148, I think it's ok here, please check D6 and R9, maybe you can using one 2K + VR10K to replace R9, and to testing the discharging time.

I only using one 1N4007 to replace 1N4001~4007, because they look almost the same, so I decided to use the same number.
View attachment 94398
Oh before I get too far ahead of myself here either Dodgydave or ScottWang,
How would I continue this scenario for my other 4 DPDT rockers? I'm not sure if I need a separate 2N2222 transistor for each switch?
And if I would do my switches in blocks like in the diagram?
Or if they just continue on branched off from what is here?
 

Dodgydave

Joined Jun 22, 2012
8,589
CD4538, Its a dual timer,

here is one half drawn to give a pulse out with a negative input pulse on pin 5, the timing is the values of RxC in seconds, so for a 1 second output pulse use 1 Meg ohms R, and 1 microfarad C, the positive pulse output is on pins 6, while pin 7 gives a negative pulse at the same time,


del10002.png


Datasheet here http://www.uni-kl.de/elektronik-lager/418169
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
CD4538, Its a dual timer,

here is one half drawn to give a pulse out with a negative input pulse on pin 5, the timing is the values of RxC in seconds, so for a 1 second output pulse use 1 Meg ohms R, and 1 microfarad C, the positive pulse output is on pins 6, while pin 7 gives a negative pulse at the same time,


View attachment 94400


Datasheet here http://www.uni-kl.de/elektronik-lager/418169
Oh wow! That is pretty cool, so I could probably get away with using one of these bad boys for all of the rockers I guess. This is something to definitely think about if I get some of those chips. But for right now I have lots of the 555 timers ;)
 

Dodgydave

Joined Jun 22, 2012
8,589
The only way i can see using one 555 timer with multiple rockers is to use diodes on the rocker switch contacts,to isolate one from the other,

the cd4538 will give the same result but with a choice of two outputs, and two trigger modes,
 

Thread Starter

Michael Knight

Joined Nov 5, 2015
90
The only way i can see using one 555 timer with multiple rockers is to use diodes on the rocker switch contacts,to isolate one from the other,

the cd4538 will give the same result but with a choice of two outputs, and two trigger modes,
Ok so they will take up a little less space circuit board wise but given I don't have them I should stick with the 555 timer option for now?
But thanks for putting me onto that CD4538 IC though as I think for future projects that could be very useful.

So on what we have how do I continue for each additional rocker switch?
 

ScottWang

Joined Aug 23, 2012
6,843
OK thanks ScottWang,
I'll give this a shot, the amount of discharge time is not totally important as it seems that when I unplug the power supply, if it is off for (and I'm guessing here) maybe a 5 or 6 second count that is more than enough time for practical day to day usage, as the ignition would be off, and by the time you started the car and started pressing buttons from the last shut off time the chip or caps should have had plenty of time to be discharged... again just guessing based on plugging it in and unplugging it.But hey if this does it faster and ensures the discharge time is faster I'm all over that my friend ;)
If you don't mind then it's ok.

Oh is there much difference between those Diodes, I see in a lot of 12V circuits that they seem to hover around those number ranges, so I had bought a bunch of different kinds in that range because I see them used a lot.?
You can say that 1N4148(100~300 mA) was designed for high frequency rectifier as f ≥50MHz and 1N4001~1n4007(1A) were designed for low frequency rectifier as 60Hz, you better use their current less than 60% of rating current.
 
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