Help re-creating a replica movie prop

[d123]

Hi,

I appreciate the effort here, gents. Thank you. But, I'm going with the YouTube video I posted last night--it's just easier for me. Even with your video, I don't know how to even start this circuit.

A couple of questions:
How can I add the 12 toggles to the YouTube circuit?
What would I need to adjust pitch and duration? Just different values of capacitors and resistors? I need a higher pitched tone and shorter duration than what was in your video, D123.

Thanks again!
John

Let me break this to you (not especially) gently, John. You can't use a monostable timer to drive a speaker because a speaker is an oscillatory device, it has a (paper) membrane that needs to oscillate to make any sound - otherwise it will just make a pathetic, barely audible crackle. The YouTube video you posted is no use to your objective, unfortunately, unless you use a DC buzzer and that will limit the sound you can reproduce to the default buzzer sound. That removes the need to answer the first question. The second question is (with an astable 555 circuit): use a smaller capacitor around the speaker and a smaller capacitor from pins 2 and 6 on the astable timer (the one to the right).

I fail to understand why a person who makes a seven-segment display circuit function - who says they had no prior electronics experience - thinks they are unable to make a simple 555/556 circuit, it seems more like stubborn caprice than truthfulness. I remember the start of this thread and you fussed over suggestions and pretty much went back to the first one suggested to you, here we go again.

Lastly - I just wanted to help you, so don't bother with the "helped me" button, it's not about "points mean prizes" for me - I'll guess that in this film you're the star of here on the forum you haven't been able to notice that people on this forum show their gratitude to the people who help them by pressing the "helped me" button, give it a try sometime and be a little less selfish/self-centred.

Sorry to be honest with you, it's not very glamour and showbiz but it is all fair comment by now...

Anyway, you need an astable timer and you're more than capable of putting that 556 circuit, or two 555s, together by yourself.

Good luck and hope it all works well for you. Thanks again!

See you!

 

[betwixt]

The toggles are the switches you already have in your existing design, you just wire the end of the diode to the existing switch that activates the display. The idea is that the diode only conducts in one direction so there is no path for any switch to interfere with another - but - any of the switches closing will trigger the beep.

Yes, the values control the length of beep and it's tone. Using the schematic in post #99, the resistor and capacitor on pins 1 & 2 of the first timer decide the length, dropping either value will make the beep shorter. I would suggest dropping the 82K value is easiest but don't go below about 1K. I would guess you want a beep about half as long so drop it to half value, maybe 39K or 47K standard values.

The idea of the first timer is it produces a fixed length single pulse when triggered by a switch closing, without it the tone would be present whenever a switch was closed. We call it 'mono-stable' timing, meaning the circuit only has one stable state which it changes to and stays at after the timing period has elapsed. The pulse is used to activate the second timer and sets the length of the beep.

The second timer is the same type of device (or other half of a dual device) but it is wired in 'astable' mode. An astable timer resets itself and keeps repeating, it doesn't have a stable state so it oscillates between two conditions. The resistors and capacitors on pins 8, 12 &13 decide how quickly it changes state and the values show make it change around 800 times a second. It is that 800 cycle changeover that drives the loudspeaker and produces the tone you hear. Again, the values decide the frequency and lower values result in shorter times which means higher pitch. In astable mode, both resistors will set the pitch but they work in slightly different ways, there are some combinations of values that will not work so I recommend dropping the capacitor value (pins 8 & 12) instead. Try 47nF to roughly double the pitch.

The pulse turning the beep on and off from the first stage goes into pin 10 of the second stage. It holds the astable part in a reset state (not oscillating) unless it is enabled by the pulse from the monostable part. So the sequence is: switch closes, monostable produces a short pulse, pulse activates astable, astable output drives speaker to make tone, pulse ends, speaker goes silent.

Brian.

 

[skarkowtsky]

Hi,



Let me break this to you (not especially) gently, John. You can't use a monostable timer to drive a speaker because a speaker is an oscillatory device, it has a (paper) membrane that needs to oscillate to make any sound - otherwise it will just make a pathetic, barely audible crackle. The YouTube video you posted is no use to your objective, unfortunately, unless you use a DC buzzer and that will limit the sound you can reproduce to the default buzzer sound. That removes the need to answer the first question. The second question is (with an astable 555 circuit): use a smaller capacitor around the speaker and a smaller capacitor from pins 2 and 6 on the astable timer (the one to the right).

I fail to understand why a person who makes a seven-segment display circuit function - who says they had no prior electronics experience - thinks they are unable to make a simple 555/556 circuit, it seems more like stubborn caprice than truthfulness. I remember the start of this thread and you fussed over suggestions and pretty much went back to the first one suggested to you, here we go again.

Lastly - I just wanted to help you, so don't bother with the "helped me" button, it's not about "points mean prizes" for me - I'll guess that in this film you're the star of here on the forum you haven't been able to notice that people on this forum show their gratitude to the people who help them by pressing the "helped me" button, give it a try sometime and be a little less selfish/self-centred.

Sorry to be honest with you, it's not very glamour and showbiz but it is all fair comment by now...

Anyway, you need an astable timer and you're more than capable of putting that 556 circuit, or two 555s, together by yourself.

Good luck and hope it all works well for you. Thanks again!

See you!

Whoa,

You just flew off the handle. Chillax. I'm not sure why you're taking this personally, or why I have to beat a dead horse and reiterate that I just don't comprehend the 555 circuit. The 7 segment circuit was much easier for me to understand. I can't tell you why.

As for the Help button: I have under 60 posts on this forum, sometimes I notice the button, most times I don't. I'm still new here and don't know the culture. It's not matter of me being self-centered or selfish. It was an honest oversight. You're being way too presumptuous about a person you've never met in the real world. No harm was meant toward your ego, which seems damaged and overly sensitive. But definitely not by me and my trivial posts about electronics.

There's a difference with you being honest and being way off base. Unfortunately, it's the latter.

Again, not sure why you are so upset with my decisions. I don't discount your knowledge or effort, I just don't understand the circuit because I'm inexperienced. You're welcome to remain in this thread and I'll forget your infantile outburst and gross generalization of my character, as I've enjoyed our conversations.

J

- - - Updated - - -

The toggles are the switches you already have in your existing design, you just wire the end of the diode to the existing switch that activates the display. The idea is that the diode only conducts in one direction so there is no path for any switch to interfere with another - but - any of the switches closing will trigger the beep.

Yes, the values control the length of beep and it's tone. Using the schematic in post #99, the resistor and capacitor on pins 1 & 2 of the first timer decide the length, dropping either value will make the beep shorter. I would suggest dropping the 82K value is easiest but don't go below about 1K. I would guess you want a beep about half as long so drop it to half value, maybe 39K or 47K standard values.

The idea of the first timer is it produces a fixed length single pulse when triggered by a switch closing, without it the tone would be present whenever a switch was closed. We call it 'mono-stable' timing, meaning the circuit only has one stable state which it changes to and stays at after the timing period has elapsed. The pulse is used to activate the second timer and sets the length of the beep.

The second timer is the same type of device (or other half of a dual device) but it is wired in 'astable' mode. An astable timer resets itself and keeps repeating, it doesn't have a stable state so it oscillates between two conditions. The resistors and capacitors on pins 8, 12 &13 decide how quickly it changes state and the values show make it change around 800 times a second. It is that 800 cycle changeover that drives the loudspeaker and produces the tone you hear. Again, the values decide the frequency and lower values result in shorter times which means higher pitch. In astable mode, both resistors will set the pitch but they work in slightly different ways, there are some combinations of values that will not work so I recommend dropping the capacitor value (pins 8 & 12) instead. Try 47nF to roughly double the pitch.

The pulse turning the beep on and off from the first stage goes into pin 10 of the second stage. It holds the astable part in a reset state (not oscillating) unless it is enabled by the pulse from the monostable part. So the sequence is: switch closes, monostable produces a short pulse, pulse activates astable, astable output drives speaker to make tone, pulse ends, speaker goes silent.

Brian.

Thank you, Brian.

 

[skarkowtsky]

Hi guys,

Would anyone be willing to confirm if this 555 circuit I created is correct? It's based on D123's initial schematic (for two 555s). I know the attached image is wonky, but I hope it's clear enough to understand. Thanks!

The image:
R = Resistor
C = Capacitor

 

[betwixt]

Looks wrong to me. Check the tracks around pin 7 of the second NE555.

You should be able to connect those grounds together and supply points together too, it will save a lot of manual wiring. Suggestion:
You need 12 diodes a resistor and a capacitor at the trigger input to the first NE555, they are not on the main display board so you would have to wire them somewhere between. Why not fit them on the new board so all you need is a single wire to each switch?

Brian.

 

[d123]

Hi,

Nice work.

If I've understood the pcb design correctly -
First 555:
· It looks like the resistor from 9V to pin 7 (and pin 6) is missing.
Second 555:
· The end of the second resistor (that starts at the end of the first resistor, the one that goes to 9V and ends at pin 7) shouldn't be connected to ground, it needs to be connected to the junction of pin6/pin 2/capacitor.
· I guess no 100 Ohm resistor from pin 3 to the speaker is needed/has been omitted deliberately (?).

Also, I agree with Brian's suggestion.

 

[skarkowtsky]

Thank you, guys. I'm following most of both of your edits. Please excuse my ignorance, when you say Diodes, are you referring to those "one direction" components, or are they the capacitors? Looking at the schematic, and again, I'm not experienced enough to fully understand a schematic, I didn't notice Diodes. But I'm certain they're there and I didn't know what to look for. Please help me figure out how to include them.

D, I most certainly removed the 100Ohm resistor to speaker by accident.

Brian, I do have this drawn down the center of the large circuit board, and there is still enough room to add more to it. Please help me include the missing components.

Thanks again, guys.

John

 

[betwixt]

They are the 'one direction' components but they are a completely different species of animal to capacitors. The 1N914 or 1N4148 (equivalents) are small glass beads with a colored band around their cathode ('-') ends. The cathode is the end the arrow points toward, the end it points away from is called the anode. From a PCB point of view, they mount the same as resistors. The only mechanical constraint is keep the legs in line with the glass body for a short distance as bending them too close can ***** the glass.

What you should consider adding is the components on the left in post #94 but add the extra capacitor and resistor in post #97. Note that you do not need the switches, they are the ones already enabling the displays. So what you should have is 12 connection points, one from each of the 12 diode cathodes to go to one of the existing display switches. The idea is that when you close any of the switches, the displays turn on and at the same time the diodes create a pulse to trigger the beep timer. It doesn't matter which diode goes to which switch, they all work identically.

Brian.

 

[skarkowtsky]

Thank you for the explanation. I think I'm following. I'll draw another circuit and post it for review.

Also, can I replace whatever resistor controls the pitch and length of the beep with a board-mounted single turn, slotted potentiometer? It will make replicating the tone a lot easier than constantly switching out different value components until I get it right. If so, which resistor(s) need to be replaced in my circuit?

Thanks again!

 

[betwixt]

For the beep length, the 82K resistor on the first NE555 needs to be adjusted. You can replace it with a potentiometer but the value shouldn't be allowed to go too low so I would suggest changing 82K to a fixed 47K resistor and adding a 50K potentiometer wired as a variable resistor (connect the wiper to one end) in series with it. That will give a range of 47K (potentiometer = 0) to 97K (potentiometer = 50K + fixed 47K).

For the beep pitch, there is a trick you can use when the NE555 is wired in astable mode like it is. Connect a potentiometer (suggest 50K ) with one end to ground, the other end to the positive supply and the wiper to pin 5 of the second NE555. Adjusting the potentiometer will change the tone but you might find it cuts out at one or both ends of the adjustment, just set it where it's needed.

Use linear potentiometers in both cases.

Brian.

 

[skarkowtsky]

I'm following. Do Diodes have values? Which value would I need for the switches?


Thanks,
John

 

[betwixt]

They don't have values in the same way as resistors and capacitors but there are thousands of different types. They tend to be rated by maximum voltage, maximum current and how fast they can turn on and off. They do have part numbers but rather like ICs, there is no particular pattern to their numbering system.

For your application speed is of no consequence (unless you can wiggle the switches millions of times a second :smile and both voltage and current are very low so I would suggest the ones to use are type 1N914 or 1N4148. They are probably the most common types ever made and cost virtually nothing. Despite having different numbers they have exactly the same specification and are 100% interchangeable. Although they will work perfectly well, I would avoid using 1N4000 series diodes which are also very common and inexpensive on the grounds that they have thicker legs and are therefore a bit harder to mount.

Brian.

 

[KlausST]

Hi,

To give a clue what "designing electronics" means:
There are manufacturers and distributors for electronic parts.
The manufacturers provide datasheets for (almost) every single part.
Distributors sell parts from many different manufacturers.
FARNELL is one if this distributors.
It lists more than 13,000 diodes. Only diodes ... and they sell all other electronic parts additionally...
A datasheet
* for a diode maybe has 4 pages,
* for a transistor 10 pages,
* for a logic IC or an Opamp or a comparator maybe 15..20 pages,
* for a modern 8 bit microcontroller maybe 300 pages.
It does not mean one needs to read every single page of every datasheet, but a good designer should at least have a good overview..
...and he needs to understand it.

Designing electronics should begin with learning the basics, school. But it will be endlessly reading datasheets..

I assume .. learning basics about diodes and so on ... can't be written in a forum post

I don't want to discourage you... do your hobby....
But if you want learn about electronics I recommend to do some courses.
Nowadays there is the internet, you will find good video courses and you will find lots of good documents...

Klaus

 

[skarkowtsky]

Hi Klaus,

Thank you for the advice. When I started this thread, it's was primarily to build the replica, and it still is. But as I've picked things up here and there from the members in this thread, I've started to reference hobbysit books on electronics. At first just to try to keep up with Brian and D123, but now because electronics is holding my interest.

Still, even with the books I'm reading, the project I'm working on is a bit advanced for me, and for that reason, I appreciate and welcome all of the help I've received thus far.

Cheers,
John

 

[betwixt]

I commend you for your persistence and willingness to learn. I've been learning electronics for the past 60 years and I'm still far from mastering it!
Your project certainly falls in the 'fairly advanced' category, if only for complexity rather than being technically difficult and it isn't one I would recommend to a complete beginner to start on.

Brian.

 

[skarkowtsky]

Hi,

I think I got it. All contacts go to traces (green is underside of board). I also tapped into the main power and ground traces from the digits. This runs down the center between both rows of digits, at the very top. Please let me know if it looks right. I labeled the screenshot as follows:

C - Capacitor
D - Diode
R - Resistor

Thanks!
John

 

[d123]

Hi,

Looks good. Is the first pull-up resistor to V+ that goes between the diodes and the series capacitor there? I can't see it labelled on the design.

A thought would be to add an 100nF (0.1uF) or a 1uF capacitor from pin 8 (V+) of each timer to ground. Reservoir capacitors are used on IC supply pins to insure against the IC seeing small voltage drops in the supply line or sudden current draws from the IC in question from seeing the voltage drop which may affect reliable performance (have a little read about decoupling and bypassing).

 

[betwixt]

It isn't a bad idea to add capacitors across supply and ground near the ICs but this circuit is almost static in operation so those voltage drops probably wouldn't cause a problem in this instance. For clocked designs they are essential.

I can see a few minor problems with the PCB, there are no pads for the loudspeaker wires and there is a track linking across each of the diodes that shouldn't be there.

Question: are you following the normal course of PCB design where you start with a schematic and generate a netlist from it or are you doing it all by hand. Both ways are perfectly feasible but using a netlist will highlight any problems as you lay out the tracks. It will tell you if there are any missing or shorted connections and may suggest (if you use autorouting) alternative and more practical ways to join points together.

There is one other trick you might be able to use but it would be extremely tedious if you are laying out entirely by hand, that is to 'flood fill' the grounds. Basically it means instead of linking ground points together with just a track, it fills all the available board area with copper and extends it to include all the ground points. It has several advantages, the most important in your design being that the resistance of the copper along the ground tracks is considerably reduced. It's a process best suited to a PCB design package as finding the optimal widths and spacings around other tracks and pads would take forever by hand.

Brian.

 

[skarkowtsky]

Hi guys,

Thank you for reviewing and correcting.

D,

The resistor is there, but I think I put in the sequence backwards. I went Diode > Capacitor > Resistor > Pin 2 of 555. If I'm following you, it seems the resistor goes before the capacitor. Is that right?

Brian,

I'm doing this all free hand. So, no Central trace to bring the switch signals up? Run them all up independently? All traces should go to a square pad that then leads out to the resistor headed toward pin 2??

I'm using a 30mm speaker with lead wires coming out of it. It won't be mounted on the board, but will be attached to the bottom of the inside of the briefcase. The idea was to just attach those leads to their connection points.

 

[betwixt]

There should be a resistor before and after the capacitor as shown in post #99.

I'm doing this all free hand. So, no Central trace to bring the switch signals up? Run them all up independently? All traces should go to a square pad that then leads out to the resistor headed toward pin 2??

There's nothing wrong with the way you are doing it but consider that the diodes go to other parts of the PC (where the switch connects to) so it would make sense to link them with a copper trace if possible to save on wiring and soldering during assembly.

I'm using a 30mm speaker with lead wires coming out of it. It won't be mounted on the board, but will be attached to the bottom of the inside of the briefcase. The idea was to just attach those leads to their connection points.

Again there is nothing technically wrong but I would suggest you add pads rather than solder to the component legs.

I have to say, and in no way am I being critical of what you have done, that designing a PCB of that complexity by hand is not something most of us would have attempted. It is FAR easier to do it with a CAD package and enter a schematic first. It would save days of your time and produce all the files ready to send for PCB manufacture automatically. Most importantly, as long as the schematic is drawn correctly, the error checking would alert you to any errors on the layout.

Hint: if you are using templates for components on the board, use a two-pin header for the loudspeaker. You don't have to actually fit the plug/socket but it will put the right sized pads on the board for you.

Brian.