Very low duty cycle oscillator circuit based on 7414 IC

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  • Last Post 01 October 2018
cd_sharp posted this 13 September 2018

Friends, I'm going to try to make an oscillator with these requirements:

  • very low, adjustable duty cycle in range 0.01% - 0.1%
  • adjustable frequency above 50 Hz
  • use IC 7414

I will use as a starting point this circuit from Chris:

which translates to:

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Chris posted this 13 September 2018

Hey CD,

For Input Pins not used, good idea to Ground them. See Video:

 

I believe this is correct unless I have missed something simple:

 

 

Note, this is not enough to achieve your Goal, extra stages are needed.

See: 74HC14 Datasheet

I redrew the Circuit from Akula's Circuit:

 

 

When you replicate the Circuit, you will see some parts are redundant, not necessary. This is a handy circuit to have on hand for simple tests!

   Chris

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cd_sharp posted this 13 September 2018

Thanks, Chris, but the circuit is a little bit different. I've put it directly in Circuit Wizard, exactly how I see it in the video, except the Pin13 connection to the ground, which the author neglected. It's more stable with it.

I prototyped it on a bread board:

It looks good, it's stable, goes from 200 Hz to about 90 KHz, and despite what's being said in the video, the variable resistor adjusts the frequency and the duty cycle at the same time.

Still, this is a step forward.

 

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Chris posted this 13 September 2018

Hey CD,

Yes, you're right, the grounding is for stability.

Excellent work! I should say, the Diodes, they are acting as Directional Devices, the Resistance on one path is different from the other path, thus the Duty Cycle can be adjusted ever so slightly, but the video is not the best way to do it, as you noted!

The stages help, start with a Frequency Stage, push this on to another stage and start looking to adjust the Duty Cycle on another Stage, this way the Duty can be adjusted without affecting the Frequency. Because they are on different stages:

 

 

I hope this makes sense.

One of my Breadboard Prototypes: Notice no Grounded Inputs in my layout...

 

 

I started the same as you!

   Chris

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Chris posted this 14 September 2018

@CD

Re-reading my last post, this may have been a little confusing.

The simplest 74HC14 Circuit is as follows:

 

 

This uses One Hex Inverter, what I meant by a Stage..

 

 

The Diode is better if its a Signal Diode, they are faster than the 1N4001's faster the better. Replace the Diode with a Resistor of the same Value as R1 and this should change the Circuit dramatically.

I am sorry if I was confusing. Also the above Circuit, the Capacitor should be Ground one leg, Pin One the other leg. I will fix this and replace the image.

   Chris

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cd_sharp posted this 14 September 2018

Thanks buddy, it's a real pleasure to think how this stuff works.

This

is this:

Also, I found out and checked practically that this controls the duty cycle only:

These are the stages, but I didn't understand yet how they can work together. I'll do some more studying.

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Chris posted this 15 September 2018

Hey CD,

The goal, Short Sharp Duty Cycle, I have tried for sometime and its not an easy goal.

I have used Microcontrollers to get some pretty good results. Thus the Microcontroller Category on the right hand side at the top under Hardware.

I have done some Arduino and also .NET Microfamework. 

About as low as I can get is 0.1 Duty Cycle, but its nice and sharp.

I can share some more data if you wish?

   Chris

cd_sharp posted this 15 September 2018

Hi, Chris! Thanks for letting me know. 0.1 duty cycle is also the limit of my function generator. I'll stick to Akula's circuit, I'll try to reverse engineer it, although that is very tough considering the low quality video of lantern no 4. I can definitely see he has 2 transistors near the integrated circuit. A mistery to solve..

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Chris posted this 15 September 2018

Hey CD,

The two Transistors are a Push Pull driver for the Coil Pulsing Transistor. You can see the Push Pull on some of Ruslan's replications:

 

 

The average Mosfet Driver is based on the same ideas:

 

Ewf: https://www.quora.com/What-is-the-purpose-of-a-MOSFET-gate-driver

 

 

Not all Mosfet Driver IC's are based on the same layout, but generally the Mosfet Gate is bought up High and bought don low as fast as the signal input requires.

 

Note: Akula used a KT805 Transistor to drive the Coils.

 

 

Its worth noting: Class A and B Amplifiers use a similar NPN PNP Transistor pair called a Push Pull Transistor Array.

 

 

I am no EE Guru, I know enough to be dangerous, but this is what I have learnt.

I would not use a Push Pull Transistor pair as in the Akula Circuit, I would replace this with a proper Ultra High Speed Driver. Way easier to get a good result!

   Chris

 

High Def is available, but only one person has it, how did they get the High De Version?

 

 

Chris posted this 15 September 2018

Hey CD,

A little research on the fastest Hex Inverter, fastest I can find is: 2.5 ns

This is the: 74LVC04

Most are around 6 to 12 ns. 2.5 ns is a big difference!

   Chris

 

Attached Files

Vidura posted this 16 September 2018

Hi Chris,

This super-fast IC are very good indeed, but we have to consider if it is really necessary , for building a nanopulser it might be a good choice, but i don't think that it's really necessary for this circuits, and if it makes much sense. A fast mosfet driver have also a rise-fall-time of 5 to 10 ns, then the mosfet and all other components AND wires -traces have an inductance,which has a notable effect when we are dealing with nanoseconds. I would guess that better improvements can be made relatively easy and cheap making a good ,clean layout and wiring, the important components close together, use the capacitors nearby the mosfet, eventually use hi frequency electrolytic caps, so you can achieve a quite fast response. I hope that this helps a little.

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Chris posted this 16 September 2018

Hey Vidura.

I agree, your' e correct!

We know Akula's Frequency was: 256.360Hz

 

 

As you know, the Period of the Frequency is: 1 / f so the Period is: 1 / 256.360Hz = 0.003900 Seconds

The On Time period is approximately: 19μs

So, we can calculate: 19μs /  3900μs = 0.004871μs * 100.00 = 0.4871% Duty Cycle.

That is approximately if my bad math is correct. 0.5% Duty Cycle is pretty easily achievable.

The only reason I bought this up was CD's specification of sub 0.1% Duty Cycles. I hope I have not confused anyone!

   Chris

cd_sharp posted this 16 September 2018

Guys, awesome info, lots of stuff to learn. I understand the push-pull circuit.

But, if it's using a NPN and a PNP transistor then why are they oriented one in reverse of the other?

I think it's most likely that the 2 transistors are identical and judging from the connections, they are NPN. I'll be posting revision 3 soon.

Again, thanks for all the help.

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cd_sharp posted this 16 September 2018

Guys, all the pots I know have 3 pins or 6 if they are stereo. The one in the image above has a leg connected to the zero voltage rail (the one closest to the integrated circuit). On the other side, the pot looks like it has 3 pins aligned on the same column (3rd column counting from the left) and one on the 5th column (closest to the IC). So, that makes 4 pins and this confuses me.

Anyone has any idea if this type of pot has 4 pins indeed and why would Akula use this type of pot?

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Chris posted this 16 September 2018

Hey CD,

A good question:

But, if it's using a NPN and a PNP transistor then why are they oriented one in reverse of the other?

 

This is because the Pins are different from NPN to PNP:

 

Guys, all the pots I know have 3 pins or 6 if they are stereo. The one in the image above has a leg connected to the zero voltage rail (the one closest to the integrated circuit). On the other side, the pot looks like it has 3 pins aligned on the same column (3rd column counting from the left) and one on the 5th column (closest to the IC). So, that makes 4 pins and this confuses me.

Anyone has any idea if this type of pot has 4 pins indeed and why would Akula use this type of pot?

 

Some, not all, some Pots ground the case, this helps stop noise and this is also to stabilize the Pot on the PCB, helps stop the breaking of connections to the pins already connected.

   Chris

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cd_sharp posted this 17 September 2018

Yes, it makes a lot of sense. Thanks!

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cd_sharp posted this 17 September 2018

Friends, this is my latest progress. with Akula lantern no 4 circuit reverse engineering:

Here I tried the driver circuit as I "read" it from the video. Very big effort:

The signal that supposedly is applied to the power transistor base is similar to this.

We know that the signal must be very sharp square wave. So, I probably "read" something wrong.

If you have any idea how to modify the above circuit to output a sharp square wave please let me know.

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Chris posted this 17 September 2018

Hey CD, whats your signal before the NPN / PNP Transistor Array Driver?

Seems there is a lot of capacitance in there?

   Chris

Vidura posted this 17 September 2018

Hey cd The transistors npn-pnp are reversed in your schematic, check it out.both emittors should go to the output(mosfet gate)

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Vidura posted this 17 September 2018

The HD version of the video is most certainly copyrighted by akula and steho energy, there seems to be a comercial relationship with OU.com also.Recently they showed a video disassembling a TPU device made by akula too.

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Chris posted this 17 September 2018

Hey CD,

I have used the MCP1403 and a few other Driver Chips. They are very easy. I have had problems with Transistor Array, getting tidy clean switching:

 

 

In the Akula Circuit, the Transistors have to be matched and biased correctly. I have just found an easier way, no fiddly messing around.

Yes, perhaps I am a little lazy when it comes to this, but the way I look at it, better things to spend my time on!

   Chris

cd_sharp posted this 18 September 2018

Hey CD, whats your signal before the NPN / PNP Transistor Array Driver?

Seems there is a lot of capacitance in there?

The signal is almost constant voltage. It's clear that I got something wrong near the IC. The capacitors values can be found only be experimenting.. Lots of work.

The transistors npn-pnp are reversed in your schematic, check it out.both emittors should go to the output(mosfet gate)

You're right.

I have just found an easier way, no fiddly messing around.

Please show me!

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Chris posted this 18 September 2018

Hey CD,

My Thread: Reliable and Flexible Switching System is where I have tried to share information on these topics.

I will tell you, these tools have made my work way easier!

I have been using Microcontrollers for some time to get to the end goal. Its a huge time saver and a very clean accurate way to take note of input settings!

   Chris

cd_sharp posted this 18 September 2018

Hey, man! Quadratron seems complex with those 4 stages. For now I just need one. I have no experience with microcontrollers.

Perhaps a basic, simple intro would be better. I'm experienced in .net, so I would prefer .NET Microframework.

I understand I need to buy some microcontrollers and a board that helps interfacing and programming the microcontrollers. That's all I know about microcontrollers.

Thanks for you guidance.

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Vidura posted this 18 September 2018

Hey CD!

I am not familiar with the .net framework, i only used microchip tools and software. 

If you want to continue with one single switch i would recommend you to use a mosfet with a mosfetdriver , the MCP1403 which suggested Chris is fine, I use  MCP1407 with a single input, these drivers are simple and will enhance the switching a lot. They can operate upto 18V supply voltage, But 12V is OK. Just connect the signal directly to the input, connect also a 100nF decoupling cap together with the supply pins of the IC , and the output pins directly to the mosfetgate, normally no other parts are required for a single mosfet.

If you which to employ it in the circuit from the video replace  R2 , C6, R5, Q1 and Q4  with the driver, the supply on C5+ and 0V.

Input IC1 pin 12 , output directly to the mosfetgate, check if you have a clean waveform on the input also.

PD: For practice with microcontrollers it would be best to purchase a board like the arduino or similar experimental tool ,some have integrated programming interface, ready to connect to your PC; and start with simple projects to become familiar with programming and so.

Good Luck!

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Chris posted this 18 September 2018

Hey Guys,

I am happy to help and share what I have learned. You don't need all 4 stages, you don't need the whole circuit, just the MCP1403 / 7 or similar Driver IC and a few resistors and Caps would be fine!

I believe Netduino is the only current .NETMF Controller on the market right now. GHI Have one of two but I don't know anywhere selling them.

It is possible to port the .NETMF to another Microcontroller with GHI Electronics .NET TinyCLR OS, but this is a bit much for now.

A very simple PWM would be:

Microsoft.SPOT.Hardware.PWM MyPWM = new PWM(Cpu.PWMChannel.PWM_4, 2, 0.01, false);

All that's required is to import the Microsoft dll: 

C:\Program Files (x86)\Microsoft .NET Micro Framework\v4.3\Assemblies\le\Microsoft.SPOT.Hardware.PWM.dll

 

 

Of course this is a very simple layout, took me no more than 15 minutes. The Driver IC is very easy to use!

The HUGE benefit, I can easily program the Micro to a huge range of parameters and easily save the settings for my records. I can share software also if you decide to go down this path.

This is really easy. I am more than happy to help, sharing is where we have a huge edge!

   Chris

cd_sharp posted this 21 September 2018

Thanks, man. Just trying to figure out what the different parts are on MCs section. In this image:

Can you please explain what is the black board and what is the red board? Why are they separately connected to USB? Which one is the one to which you are uploading your program?

I guess they are both connected to your development laptop/PC, right?

I don't know what to buy for this project and for getting started with MCs. If you have recommendations, please let me know!

Chris posted this 21 September 2018

Hey CD,

GHI Electronics used to make and supply the parts:

 

Breakout:

 

USB-Serial SP Module:

USB-Serial Module:

 

FEZ Cerberus Mainboard:

All parts are part of the Gageteer Series. A great idea, seems to many pulled the plug too early!

Its entirely up to you, what you look at if any, but I would recommend looking at: Netduino

   Chris

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cd_sharp posted this 23 September 2018

Guys, let's say in this circuit, the MOSFET is fully open at 20V gate-source voltage (which is the case of IRF3205) and the microcontroller (or IC) signal is 5V, square wave.

How can I deliver a 20V signal to the gate of the MOSFET? Should I use a voltage quadrupler like this?

Wouldn't this affect the square wave? Should I connect the voltage quadrupler between the MOSFET driver and the gate?

Thanks

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Chris posted this 23 September 2018

Hey CD,

Please remember, my Electronics skills are only enough to be dangerous, I am not skilled in the Art! However, I will try to answer the best to my ability.

The IRF3205 Datasheet, shows a Max Gate voltage of ±20 Volts:

 

 

This means you want to stay below  ±20 Volts.

The Datasheet shows Gate Voltage Plot:

 

 

The Maximum Gate Voltage shown in this Plot is 12 Volts, well below the Maximum Rated  ±20 Volts.

There are many solutions, and it depends on your requirements, but one solution would be to use a DC to DC Converter:

Isolated Board Mount DC/DC Converter, 2 Output, 2 W, 15 V, 66 mA, -15 V, 66 mA

 

 

On a lot of PCB's you will see circuitry like so:

 

 

It seems to be more so standard practice to implement DC Converters when a voltage change is required, this is why I chose this option first.

Or, as I have shown above, have your source Voltage at the required Voltage, say 15 Volts, and step down this supply to 5 volt or 3.3 volt using a Voltage Regulator:

 

 

The same can be done with a 3.3 Volt Regulator.

In my circuit:

 

 

I had a 12 Volt Source Supply, marked as VCC, and the following circuitry stepped down, and supplied, 5 Volts, (USB Cable) and 3.3 Volts, (small PCB Mount Voltage Regulator) to the Microcontroller using the following part:

 

USB-Serial SP Module:

 

Its worth noting, most Mosfet Circuits incorporate an 18 Volt Zener Diode for Gate protection, sometimes back to back:

Where D1 and D2 are Zener Diodes rated to 18 Volts. Meaning anything over 18 Volts is dumped to Ground. D1 might be a Ultra Fast Diode in some cases, and not a Zener Diode.  The purpose of D1 is to stop the Mosfet turning on from reverse stray voltages. In this case one would not use R1, the pull down resistor and a proper Mosfet Driver to pull down the Mosfet.

So, it is common to use 12 to 15 volts as the Gate Voltage for Mosfets.

Please note, again, I am not skilled in the art, so others much more knowledgeable than me please correct me where I am not correct.

   Chris

 

P.S: The VCC Pin on the Mosfet Driver, Pin 6 in the Datasheet marked as VDD, for the MCP1403 Driver, is the voltage supplied to the Mosfet Gate. No other Circuitry is required.

 

MCP1403 Mosfet Driver Circuit

 

For those skilled in the art, they already know my terminology is not correct:

VCC stands for "voltage at the common collector"

 

VDD stands for "Voltage Drain Drain"

 

Technically Vcc/Vee is for bipolar and Vdd/Vss for FETs, but in practise today Vcc and Vdd mean the same, and Vee and Vss mean the same.

And, Voltage Source Symbols should be marked as:

 

 

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cd_sharp posted this 24 September 2018

You're right, it fully opens at 12V. I checked. Lots of new stuff for me, thanks!

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Chris posted this 24 September 2018

Hey CD,

Of course Transistors ae not the same and turn on under slightly different circumstances:

 

 

But we are still inline with the Akula Circuit, using a Mosfet Driver with a Transistor.

   Chris

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cd_sharp posted this 24 September 2018

That's a weird thing that in the first part of the video, his pulses are consistent with the presence of a power transistor (like he says, KT805), but I obtained the "good" results using a MOSFET and some extra capacitors.

That's why I believe that Lantern no 4 achieves LL resonance using a RLC resonant tank from L1 and the 2 electrolytic capacitors and the other RLC resonant tank from L2 and the LEDs.

Akula does not show the traces while the device is working, so this is just a theory, which I'll try to prove.

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Chris posted this 24 September 2018

Hey CD,

There is Magnetic Resonance in the Coils and the Capacitors offset the Coils Distributed Capacitance.

@: 11 : 12

 

 

You are correct, but if I may push you toward the Coil Interactions.

 

 

Its the same as The Mr Preva Experiment, but we have very short pulses bringing the RLC Coil combination into resonance, this is because we have induced a Voltage on the Terminals on the Coils at the right Frequency.

We have Antenna Theory basics playing a role here, Frequency and Duty Cycle bring a Harmonic Magnetic Resonance about.

E.G: Change the Frequency and Duty Cycle and we loose the effect... No Resonance.

In the Thread: Rogue waves and negentropy, we saw Ocean Waves Slapping together, they in turn create Standing Waves very much higher then the incident waves. This Slapping together is where Excess Electromagnetic Induction occurs!

 

 

 

The Coils must be thought of, as having an Electromagnetic Wave that accompanies the Current, movement of Charge, when Resonant, as in Antenna Theory, The Green arrows indicating the Slapping Together of the Magnetic Fields ( B ) ( Destructive Interference ), the Standing Waves Created, where the more ferociously the Slapping together ( E.M.F = -NdΦ/dt ), the higher the Standing Wave ( Constructive Interference ), in this case the Current, indicated as the Electric Field ( E ): 

 

 

For some, there may be a Relationship falling into place here? I hope what I have shared has been helpful!

   Chris

 

P.S: The Relationship to Antenna Theory is why History has shown most skeptics to make the Assumption, these devices work from, or draw Power from, the local Radio Stations, of course an incorrect and unbalanced theory, only a solution for a mind that can not fathom a higher level of understanding of the underlaying phenomena!

Now we have many Genius, Guru, Statues wink

 

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cd_sharp posted this 30 September 2018

My friend, very nice info.

Getting back to the 7414 based oscillator, since we know for sure that this controls the duty cycle using the 1K pot:

and the frequency is controlled by the C1 cap charging and discharging (fact that I checked using 7414 IC), then there is a problem. How do we make the cap bigger or smaller?

Since around 100nF variable caps are rare (I did not find one) the answer is that we don't make it bigger or smaller.

We just need to make it charge and discharge slower or faster:

I'll do some testing on this circuit and keep you updated.

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Chris posted this 30 September 2018

Hey CD,

Apologies for getting off topic!

Nice work my friend! The following may be of some use, I hope!

The 7414 Oscillator is based on an RC Time Constant. Resistance in Ohms times Capacitance in Farad's gives Time in Seconds. Frequency = 1 / T, however we have a 1.2, so this must be due to IC rise/delay times.

There is a Calculator here: 7414 Oscillator Calculator

 

 

Frequency = 1.2 / ( Resistance * Capacitance )

 

In Akula's Circuit, I unfortunately am not able to definitively tell you exactly which Capacitor and Resistor combination will give you the Frequency. My experiments gave me mixed results.

Not forgetting we are using Hex Inverter, each stage is Inverting the Signal, so 99.53% Duty Cycle on one stage will give 0.47% Duty Cycle after an Inverting Stage.

 

 

Circuit Wizard File attached Below.

 

 

Thus, the 1.2.

I hope this helps some!

   Chris

Attached Files

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cd_sharp posted this 01 October 2018

Here is one version of the oscillator:

The duty cycle is jumping from 99.01 to 99.5%. It's probably a reading problem of the oscilloscope because the waveform has some small ringing at rise and fall times.

I have another idea to improve. I'll be back on this.

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Chris posted this 01 October 2018

Beautiful Work CD!

Really nice clean waveforms there!

Very odd readings for Duty Cycle. Try winding the resolution out, fit more samples on the Scope. Seems there is a resolution problem of sorts there. You should have around 0.7 or so Duty Cycle and not 90.1.

Also, check and make sure the probes are not inverted, although this should not give you this problem. DUP, scope says its off...

Very nice work CD, that wave form is nice! 

   Chris

cd_sharp posted this 01 October 2018

My mistake, the oscilloscope has both duty cycle+ and duty cycle-. So, the duty cycle is, as you said, between 0.5 and 1.

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