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  • The inventor of our preferred circuit 555 timer died this year 8.8.2012 - 78 years old.


    For those being able to read German: Here a excellent compendium of all 555 types.
    Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

    Comment


    • Rise and Fall time vs. Frequency

      Dedicated to member bobfrench
      There were several discussions regarding max. frequency. Let's take the example of 555 timer IC. It is BTW worldwide the most sold IC.
      We focus on the modern design in CMOS LMC555. They write in the data sheet 3MHz and rise & fall time 15 ns. Now: How do those values relate?
      The frequency period of 3MHz is 333 ns. At 50% duty cycle we talk of a pulse time of 167 ns.
      We understand now that the output circuit is occupied 2 times of 15ns for rising and ceasing voltage so the net high time is 137 ns left. Conversely: about 22% of time is being spent in order to travel along the voltage slope low / high and vice versa.
      Those values apply to 5V operating voltage. At lower voltage the slopes are more flat while at higher voltage the slopes becoem steeper. They do not give exact values but the max frequency: 5V -> 3MHz / 12V -> 4.0 ....5.6 MHz. We comprehend the LMC 555 being slightly faster at higher voltages.
      But let's focus to 5V voltage.
      The max. frequency is determined by the overall delays of all internal circuitry. They state that the delay from trigger to output reaction is 100ns.
      Given we could make the internal circuitry much more faster, then the output stage could perform with higher frequency along signal quality geting worse beacause the slopes do not change at all. But the high time will decrease down to 30ns pulse length. There we will get a distorted triangle with no real high time. (please understand this is theoretically!)

      Imagine a mountain climber. He will be able to ascend 5000m along 15 days. So you can compute how many meters he will overcome a day or how long he will require to ascend 1m or 100m .....
      Same at 555: 15ns for 5V corresponds to:
      - 1V within 3ns
      or
      - 0.333V per ns
      or
      - 333V per µs (theoretically!)
      This way the slopes are defined in electronics.

      Of course under load the output will take more time like our mountain climber loaded wirth a heavy backpack.

      Comprehending this we will accept that a pulse length of 1µs will be viable. we spend 30ns for overcoming the slopes and have 1000n-30ns=970ns real high time. BTW: At duty cycle of 50% this will give a frequency of 2 times 1µs = 500KHz.

      The bad news is that at driver stage it gets much more worse. Recall - we overcame 5V within 15ns without any load. A gate from FET is a heavy load of 1nF capacitance - despite short time only -> essential. In fact there are som other drawbacks form drain leg so the total computation will give about 12 nF load.
      Therefore it is important to not drive more than 2 FETs by one 555 being mounted near by.

      Going further let's imagine to have a FET driver for 100V. We expect it to overcome edges at 15 ns as well in order to have a good pulse. Instead 5V in 15ns we expect 100V in 15 ns -> factor 20!!!!!
      - 1V within 0.15ns = 150ps
      or
      - 6.66V per ns
      or
      - 6 666V per µs (theoretically!)
      We comprehend that we expect much steeper slopes than we had before. That is a serious challange to build. With normal commercial drivers this is not achievable. The data sheets give their switching speeds related to commercial drivers not being specified.
      Nevertheless FETs are extremely fast - given we can move several amps in and out of the gate capacity withn ns time range. In laser technology they gernerate pulses down to sub nanosecond range - but that is serious science. Length of wires and their diameter are absolutely essential and do influence performance more than components. Ther electronics becoms joined with mechanics.

      Commercially available driver
      A good commercial driver but limited to about 500Khz
      some basic Annotations for driving FETs
      JohnS
      Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

      Comment


      • Fas FET switching

        JohnS,

        This is great. We've got a whole forum to ourselve. Just kidding, this much better than posting on the motor forum. Thank you.

        Your information and illustrations were very clear, thank you. It looks like what I want to try is very possible. Now, if I don't use an extremely high frequency, say 100-200kHz, will the 555the allow me to turn the duty cycle down to where the ON time is less than 1a micro second? BTW, how is the ON time designated on a data sheet for a FET? What is it called?

        So far I am planning on making a bi-filar coil of two 22AWG wires and placing one of them across the battery terminals, swithing it with a FET, fast enough to prevent the ions (not electrons) in the battery from moving in the discharge direction. The other wire will go to the A/C side of a full wave bridge rectifier and, hopefully, I will get something out od the DC side (DC or radiant). As long as the ions don't move in the discharge direction the battery stays charged. Free energy. We'll see.

        I want to do this experiment on a 12v battery and I hope 0 amps will be coming out of it into the FET. According to Tom, if we switch OFF within a micro second, then no current flows, just potential.

        I looked at and copied the material on the links you provided. I will read all of it. Digi-Key has LT8610s for $4.36-8.34 each. Not cheap, but if this is better than a 555...oh, well.

        Thanks again, cheers,

        Bob
        Originally posted by JohnStone View Post
        Dedicated to member bobfrench
        There were several discussions regarding max. frequency. Let's take the example of 555 timer IC. It is BTW worldwide the most sold IC.
        We focus on the modern design in CMOS LMC555. They write in the data sheet 3MHz and rise & fall time 15 ns. Now: How do those values relate?
        The frequency period of 3MHz is 333 ns. At 50% duty cycle we talk of a pulse time of 167 ns.
        We understand now that the output circuit is occupied 2 times of 15ns for rising and ceasing voltage so the net high time is 137 ns left. Conversely: about 22% of time is being spent in order to travel along the voltage slope low / high and vice versa.
        Those values apply to 5V operating voltage. At lower voltage the slopes are more flat while at higher voltage the slopes becoem steeper. They do not give exact values but the max frequency: 5V -> 3MHz / 12V -> 4.0 ....5.6 MHz. We comprehend the LMC 555 being slightly faster at higher voltages.
        But let's focus to 5V voltage.
        The max. frequency is determined by the overall delays of all internal circuitry. They state that the delay from trigger to output reaction is 100ns.
        Given we could make the internal circuitry much more faster, then the output stage could perform with higher frequency along signal quality geting worse beacause the slopes do not change at all. But the high time will decrease down to 30ns pulse length. There we will get a distorted triangle with no real high time. (please understand this is theoretically!)

        Imagine a mountain climber. He will be able to ascend 5000m along 15 days. So you can compute how many meters he will overcome a day or how long he will require to ascend 1m or 100m .....
        Same at 555: 15ns for 5V corresponds to:
        - 1V within 3ns
        or
        - 0.333V per ns
        or
        - 333V per µs (theoretically!)
        This way the slopes are defined in electronics.

        Of course under load the output will take more time like our mountain climber loaded wirth a heavy backpack.

        Comprehending this we will accept that a pulse length of 1µs will be viable. we spend 30ns for overcoming the slopes and have 1000n-30ns=970ns real high time. BTW: At duty cycle of 50% this will give a frequency of 2 times 1µs = 500KHz.

        The bad news is that at driver stage it gets much more worse. Recall - we overcame 5V within 15ns without any load. A gate from FET is a heavy load of 1nF capacitance - despite short time only -> essential. In fact there are som other drawbacks form drain leg so the total computation will give about 12 nF load.
        Therefore it is important to not drive more than 2 FETs by one 555 being mounted near by.

        Going further let's imagine to have a FET driver for 100V. We expect it to overcome edges at 15 ns as well in order to have a good pulse. Instead 5V in 15ns we expect 100V in 15 ns -> factor 20!!!!!
        - 1V within 0.15ns = 150ps
        or
        - 6.66V per ns
        or
        - 6 666V per µs (theoretically!)
        We comprehend that we expect much steeper slopes than we had before. That is a serious challange to build. With normal commercial drivers this is not achievable. The data sheets give their switching speeds related to commercial drivers not being specified.
        Nevertheless FETs are extremely fast - given we can move several amps in and out of the gate capacity withn ns time range. In laser technology they gernerate pulses down to sub nanosecond range - but that is serious science. Length of wires and their diameter are absolutely essential and do influence performance more than components. Ther electronics becoms joined with mechanics.

        Commercially available driver
        A good commercial driver but limited to about 500Khz
        some basic Annotations for driving FETs
        JohnS

        Comment


        • Hi Bob,
          unfortunately the 1µs pulse corresponds to 1µs high followed by 1µs low = 2µs period = 500 KHz. Same state if you have 1µs high and 1000µs low.
          The muscles auf a mountain climber will not be able to ascend faster if you promize him 1000 days idling after his excessive effort.

          Important to know: The propagation of electric current in wires performs with about 0.85 * luminal speed.

          The docs I posted shall show the complexity of this matter. There are plenty of solutions, dissertations ... out there. Many of them apply special behaviours of semiconductors. I had a list of links but I lost it recently - don't know how.

          I am very interested as well in fast pulses but I focus now an my motor first.

          Nevertheless: An additional background:
          We have to charge/discharge about 12nF within nanoseconds. Why:
          The gate capacitance is 1nF - OK so far.
          There is another capacitance from drain to gate. Unfortunately this is charged initially before switch on - up to i.e. 100V. In the very same moment if I try to switch the FET on, the drain voltage drops and sucks charge/current out of my gate. We need to feed this current as well.
          Switch on is comfortable because I can have 20V driving voltage while needing 10V for fill on.
          Switch off is worse because I need to go below 4V and have GND level only -> slower. And of course the drain/ gate cap will feed current into the gate as sonn as the drain voltage increases.

          My idea:
          The FET will perform up to 20V max. for gate voltage. Now I provide 60V gate voltage and switch it via a tuned cap, I have initially a very high voltage diffference and thus high amps (i.e. 5 amps). The tuned cap will charge up and will limit the current but - AFTER it dropped excessive amps into the gate. The idea is to use the high voltage difference (= high amps) first and stop the gate capacitance from getting overvoltage.
          It is like using a hammer in order to get nails into wood. A half pound hammer can press with up to 8 tons - for very short itme in order to get the nail moving.
          Same at switch off with neg. voltage. Pump excessive amps for short time and limit the charge in the gate to i.e. -1V.

          There is a schematic out there with 3 FETs and +60 / -40V driving voltge. I will provide the link if I find it.

          Please do not imagine to get this easily. The implications are in the detail. We need fast scopes and excessive short and thick conductor bars.
          Apart that your scope probe tends to show artifacts not being in your circuit in reality. You need a porbe with a GND lead directly at the tip.

          So far my current notion
          rgds
          John

          EDIT: Just found: Perhaps you will appreciate this ready made work:
          They used a RF FET 1.4 Ohm but we need not supply much current but a voltage shock! This circuit can pulse up to 1200V and down to 20ns pulse width. 40A single pulses!

          EDIT: Just detected the driver is obsolete and therefore you find excessive prices only. But IXYS offer a full bunch of different drivers and pulse modules. So the RF rail is the way to go. i.e. example 6€ and slightly slower.
          Apart that they have an application note where they say that leads of more than 9mm are not acceptable at all. Bias caps for power need to be soldered DIRECTLY on the leads of the driver .....
          Last edited by JohnStone; 10-22-2012, 03:24 PM.
          Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

          Comment


          • Hi Bob,
            why do you choose a switched regulator for pulse generation?
            One step is generating a frequency for pulse repetition. This can be done by a LMC555 easily. Do not care for duty cycle there.
            For pulse width you do not need to sweep a big range - so you have good options to choose:
            1. For this we find simple circuits. i.e. Zero Crossing Detectors second pic.
            2. Another approach can be to start two Monoflops (74HC123) at same trigger time by your oscillator. The monoflops have slightly different timing. By fine tuning you can generate extremely short pulses with much slower circuits.
            see http://www.edn.com/file/21978-51100di.pdf article Scroll to article "Simple circuit produces a less-than-25-nsec pulse"
            Last edited by JohnStone; 10-22-2012, 07:12 PM.
            Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

            Comment


            • Choosing a circuit

              JohnS,

              I am completely open to any suggestion you have as to what circuit to use. I lean toward simplicity whenever possible, I only want to get good 1us (or less) switching. I thought the Frequency Generator that you gave was "the thing" for this, but as you explained it is not.

              The frequency can be anything that helps get the 1us. Having some time in between ON times will allow the ions to lose any momentum that the switching may cause in them. I would guess that anything between 25kHz and 250kHz would suffice.

              Looking at the circuits you linked to I see the 74HC86 circuit is the 2nd pic. Is that the one you were suggesting that I look at? This circuit would run over 100kHz and the delays seemed to all be in the 11ns to 50ns range. Would this circuit allow an ON/OFF time of 1us or less?

              If this circuit will work well for me, will I need the following Comparator circuit with it to make sharp signals? Are there other sections that I will need to add on in order to run the FET?

              Also, somewhere in all that I remember something about sending a neg signal to shut off the FET quickly or sharply. Is that a consideration?

              The "Low cost 2GHz" circuit was strictly between 2.3 and 2.5GHz. That seems excessive at this point and I'm not sure if the ions would see that more as a constant ON. (?) Might be something to try later. (?)

              I hope that I don't wear you out with my ignorance of electronics. I am going to find some kind of an electronics glossary. If I get the terminology down I will be able to put things in context. I'm very good with systems...once I get the facts.

              Thanks again, buddy,

              Bob

              Originally posted by JohnStone View Post
              Hi Bob,
              why do you choose a switched regulator for pulse generation?
              One step is generating a frequency for pulse repetition. This can be done by a LMC555 easily. Do not care for duty cycle there.
              For pulse width you do not need to sweep a big range - so you have good options to choose:
              1. For this we find simple circuits. i.e. Zero Crossing Detectors second pic.
              2. Another approach can be to start two Monoflops (74HC123) at same trigger time by your oscillator. The monoflops have slightly different timing. By fine tuning you can generate extremely short pulses with much slower circuits.
              see http://www.edn.com/file/21978-51100di.pdf article Scroll to article "Simple circuit produces a less-than-25-nsec pulse"

              Comment


              • Hi Bob,
                you are welcome to ask any question.
                I try to give a bit of overview in order to help you to adjust and know precisely what you need. I know this is confusing sometimes but it is better than suggesting one single possibility without any learning effect at your side. You learn here more than your feeling tells you - believe it!.

                1. The generator I suggested is a quality circuit and it is suitable up to 1 MHz (with some drawbacks). The duty cycle adjustment within that generator is not suitable for your application because it will end far from the pulsewidth you focus on. So please understand that your application begins somewhere where UFOs initial teaching ended. It was intedend to educate basic pulsing of coils. Therefore you get some additional suggestions from me

                2.
                All driving circutis I suggeted focus an quite normal FET driving. What I detected yesterday is that the current technology in FR FETs is far advanced compared to my knowledge before. Therefore I posted that pulsing doc for food application.

                4.
                So look at the folowing buildiung blocks:

                A: My generator including duty cycle. It is easy to test and can be used for whatever you want - general purpose.

                B: "Simple circuit produces a less-than-25-nsec pulse" .... you generate very narrow pulses far from what any normal generator can do. This is YOUR special add on to the generator. This is the signal only - no driver capability requested here. And it is dead simple. But please

                C: IXYS driver 20amps. Dedicated and near to the RF FET. Low power input. Good separation from all generator action. The driver satisfies all requirements for the FET. Please do not believe this circuit is beyound your needs. In practical use you will have drawbacks and possibly not get 20ns pulses. But it is good to have pulses as narrow as possible because you do not want to operate at lower limits where you possibly can just see some dim OU effects.
                And prepare to apply SHORT / HEAVY wires

                D: IXYS RF FET - your valve to OU
                Prepare for cooling your FET. And prepare to apply SHORT / HEAVY wires

                E: HV PSU
                As you possibly detected that pulsing circuit is being driven by a 9V battery block and HV generator added. The pulses kick with excessive amps but for short time (kick with a hammer) and low repetition rate.
                For first trials it is suitable to start with 12V but do not expect miracles. The OU effects increase excessively with pulses being narrow and high voltage. It is essential to hit the ether with a small hammer with excessicve speed (voltage)
                So you will shurely come to require HV pulses. For beginning try to use a CFL electronics or a HV PSU from a CCFL tube from a flat screen. They generate pulses of about 1 KV and you easily can rectify them (HV diode) and store them in a HV cap ready for use. Or you use an old flashlight. The generate about 400V at flash tube (this voltage can be lethal !!!!!)

                The suggestions above would be my trail to narrow pulses and in fact you led me to think these thoughts now so I myself can prepare to do the same. Thanks for your kick
                JohnS
                Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

                Comment


                • Nature of square waves

                  Tha basic wave form of any oscillation is the sine wave. This is the natural property of oscillations.
                  But we know that there are lots of other waveforms in use. In order to understand and calculate those forms and to preemt their effect it is usual to decompose them into a bunch of sine waves of different frequency and amplitude. And of course the effects and the processing of sine wevaes is well known.
                  The mathematician Fourier demonstarted this decomposition first time and therefore its name is "Fourier Transformation / Analysis".
                  Conversely we can synthesize any wave by summing up a bunch of well tuned sine frequencies.
                  We will focus here on square waves.
                  It easily understandable that a square wave of 50% duty cycle conatains a basic sine wave fitting exactly inside the square wave. The question is what additional waves are necessary in order to fill up the missing areas.
                  Notion in advance: The additions will be higher frequencies and they will have less amplitude.
                  Please study the Figure 1-4.2 Spectra of some commonly occurring waveforms (here).
                  The graphs show that a square wave contains additional frequencies with odd factors 3f, 5f .......
                  The more components we add the more we can generate sharp vertices.

                  The notions above relate to a square wave with 50% duty cycle. The conditions change dramatically if we generate narrow pulses. see

                  The notions above shall explain why it is important to obey general RF considerations if dealing i.e. with a pulse of 1µs. The consideartion of corresponding 1MHz relates to the basic wave contained therein only. Considering the linked docs above we easily can see that pulse shaping frequencies of 3,5,7 ... MHz will be necessary additionally if 50% duty cycle and lots of requencies inbetween if we have narrow pulses.
                  It shall be understood that any frequency component represents a certain chunk of energy as part of the overall energy of the square signal.

                  The explanations above shall demonstrate the fact that seemingly "simple" circuits need to be built with components of much higher rating and additionally the length and quality of leads and wire influnce the function consiedrably.
                  It should be understood that at higher frequencies a certain length of wire can be a cap or inductance or resistor. Thus they can add to tank circuits performing spurious oscillations or as lambda/4 aerials transmitting and receiving spurious noise.

                  I do not want to enter deeper in the matter. The notions above are suffitient in order to understand why it is important to consider mechanic dimensions while construcing any setups for pulsing OU effects.
                  Omitting those hints you will cut the vertices of your pulse away and free considerable enrgy for spurious disturbanceis.

                  First implications start with frequencies above 20 KHz and get more and more serious with narrow pulses and higher repetition frequency. Many setups do not funtion properly because they omit the hints above. Please understand that a circuit digram is only a small segment of a real circuit representing the physical connections only.

                  I ask you kindly to obey and understand any hints regarding how to connect ground lines, how to do connections mechanically. High currents (i.e. 20A for a gate drive for a FET) and RF need to be considered. The only differenc to commercial high power and RF setups ist that we do not apply energy continuously. The basic requirements for performing the functions intended are the same.
                  JohnS
                  Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

                  Comment


                  • 1st step

                    OK JohnS,

                    I'm at work, so I can't go into detail on what I understand from your last post. I'll get that out later today, but t looks great so far.

                    Let me clarify one thing though. What I am trying to do with this particular experiment is not to get spikes. I know that sounds like blasphemy, but this other is intriguing. The switching is only providing gating for the voltage coming out of the battery such that the ions don't move (only the charges). The voltage will come out normally, just 12v (24, 36, 48...), but it will be "free".

                    "I'll be back,"

                    Bob


                    Originally posted by JohnStone View Post
                    Hi Bob,
                    you are welcome to ask any question.
                    I try to give a bit of overview in order to help you to adjust and know precisely what you need. I know this is confusing sometimes but it is better than suggesting one single possibility without any learning effect at your side. You learn here more than your feeling tells you - believe it!.

                    1. The generator I suggested is a quality circuit and it is suitable up to 1 MHz (with some drawbacks). The duty cycle adjustment within that generator is not suitable for your application because it will end far from the pulsewidth you focus on. So please understand that your application begins somewhere where UFOs initial teaching ended. It was intedend to educate basic pulsing of coils. Therefore you get some additional suggestions from me

                    2.
                    All driving circutis I suggeted focus an quite normal FET driving. What I detected yesterday is that the current technology in FR FETs is far advanced compared to my knowledge before. Therefore I posted that pulsing doc for food application.

                    4.
                    So look at the folowing buildiung blocks:

                    A: My generator including duty cycle. It is easy to test and can be used for whatever you want - general purpose.

                    B: "Simple circuit produces a less-than-25-nsec pulse" .... you generate very narrow pulses far from what any normal generator can do. This is YOUR special add on to the generator. This is the signal only - no driver capability requested here. And it is dead simple. But please

                    C: IXYS driver 20amps. Dedicated and near to the RF FET. Low power input. Good separation from all generator action. The driver satisfies all requirements for the FET. Please do not believe this circuit is beyound your needs. In practical use you will have drawbacks and possibly not get 20ns pulses. But it is good to have pulses as narrow as possible because you do not want to operate at lower limits where you possibly can just see some dim OU effects.
                    And prepare to apply SHORT / HEAVY wires

                    D: IXYS RF FET - your valve to OU
                    Prepare for cooling your FET. And prepare to apply SHORT / HEAVY wires

                    E: HV PSU
                    As you possibly detected that pulsing circuit is being driven by a 9V battery block and HV generator added. The pulses kick with excessive amps but for short time (kick with a hammer) and low repetition rate.
                    For first trials it is suitable to start with 12V but do not expect miracles. The OU effects increase excessively with pulses being narrow and high voltage. It is essential to hit the ether with a small hammer with excessicve speed (voltage)
                    So you will shurely come to require HV pulses. For beginning try to use a CFL electronics or a HV PSU from a CCFL tube from a flat screen. They generate pulses of about 1 KV and you easily can rectify them (HV diode) and store them in a HV cap ready for use. Or you use an old flashlight. The generate about 400V at flash tube (this voltage can be lethal !!!!!)

                    The suggestions above would be my trail to narrow pulses and in fact you led me to think these thoughts now so I myself can prepare to do the same. Thanks for your kick
                    JohnS

                    Comment


                    • Summary

                      JohnS,

                      Yes, this sounds so good. These in series:

                      A- Your frequency generator

                      B- 25ns add-on ("Simple circuit...25ns pulse")

                      C- IXYS Driver 20A

                      D- IXYS RF FET

                      I assume this next one feeds just the RF FET:

                      E- HV PSU

                      I will look into the RF FET. I'm unfamiliar with it. I'm still wondering, if this works as I hope and no amp draw/only potential, will the FET heat up at all? I will provide a heatsink anyways.

                      Am I right that the HV PSU is to supply the FET only?

                      I already have the components for building your frequency generator ordered. The rest won't be much. I hope to get this thing off the ground soon. Cool!

                      Thanks,

                      Bob

                      Originally posted by bobfrench@fastmail.fm View Post
                      OK JohnS,

                      I'm at work, so I can't go into detail on what I understand from your last post. I'll get that out later today, but t looks great so far.

                      Let me clarify one thing though. What I am trying to do with this particular experiment is not to get spikes. I know that sounds like blasphemy, but this other is intriguing. The switching is only providing gating for the voltage coming out of the battery such that the ions don't move (only the charges). The voltage will come out normally, just 12v (24, 36, 48...), but it will be "free".

                      "I'll be back,"

                      Bob

                      Comment


                      • JohnS,

                        I looked at the IXYS stuff. Is the IXZR16N60 (600V, 18A, 350W) or IXZR08N120 (1200V, 8A, 250W) what you had in mind? This must be state-of-the-art stuff.

                        Comment


                        • JohnS,

                          I just looked at the RF FET driver, DEIC515 (8-25V, 15A max.,45MHz, ins rise and fall times, 8ns pulse width!) and for only $46.13! Pricy, but it might allow us to do some things that we haven't imagined yet.

                          This seems like a little overkill, but if you think that it is the way to go, then I'm OK with it.

                          Bob

                          Comment


                          • JohnS,

                            That was supposed to be a "4ns" rise and fall times, but my computer changed it to "ins" and I didn't catch it in time.

                            Let me know what you think and I'll order things accordingly.

                            Having this capability this close now is unbelievable.

                            Bob

                            Comment


                            • Hi Bob,
                              I'm at work now. Just some hints.

                              1. The driver you mentioned is no longer available - therefore that space price . But there are others for about 4 €.
                              Give me some days in order to look for "second" level and affordable.
                              And yes you can start with some standard components below 15$. If you destroy tehm by accident it is affordable as learning fee.

                              What is your local source for components? Farnell? Digikey?

                              For later high end pulsing all in one modules are recommended i.e.:
                              IXYS: have one driver and FET in one casing but expensive as well. Those are top level solutions we can convert to when time has come.
                              Microsemi: http://www2.microsemi.com/datasheets/drf1200_a.pdf
                              Please note that in this area the whole machanics is essential (see eval board in pdf above). With usual FET / driver cases you can not improve considerably - mechanics is the limit.

                              2. Even if you target to 1µs please take in account that the steepness of edges fosters OU as well. The ingredients are peak voltage, abrupt voltage change and shortness of pulses. We can not abbandon all at same time.

                              3. I focussed on switch action to GND. But now I got your application in my mind - direct battery charge. Now there is the issue on how to connect batteries to such a switch. The switch is not GND based in your application. I have an idea. Give me some time to ponder on it in order to keep it easy.
                              Prepare to get some socket chargers in order to have different separated voltage sources your setup (generator, driver ...)

                              4. Yes HV is for supplying the load on the RF FET. You shurely will come to those applications later on. So be prepared.

                              5. Have you got an oscilloscope? You will need one in order to verify your pulses for quality. 100MHz shall be minimum of resolution. Digital storage will be essential for catching single pulses.

                              6. FETs with high amp draw are no overkill at all. Any failure will evaporate small FETs. So stay secure and use FETs with 10 amps as well. Do not focus on absolute maximum data. They often relate to single pulse once every 20 ms.

                              7. In summary: You will build an affordable driver/FET assembly with minor drawback but prepared for some other experiments after your battery setup. For upgrade it will be advisabel to buy singel modules (driver/FET) because those have superiour properties and you will be able to replicate tehm easily in your setup. some 30 or 40$ will be not too much if you enter in serious research. Most of us trickle more money into sink by starting several trials and destroying components by accident.

                              8. Be prepared to connect batteries with THICK wires. Any additional resistance (real or complex) will reduce the effecs you are after.
                              rgds John
                              Last edited by JohnStone; 10-24-2012, 02:38 PM.
                              Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

                              Comment


                              • Hi Bob,
                                regarding your batteries:
                                • You obviously need to have more voltage at primary batteries i.e. 36V - three in series.
                                • You want to pulse voltage but no amperage into the secondaries i.e. three 12V in parallel.
                                • Use short heavy leads.
                                • Your generator, driver, FET neet to be completely earth free. Check it!
                                • Your battery system needs to be completely earth free.
                                • You can insert your FET between + leads: FET drain to the source battery, FET source to the seconary batteries.
                                • Mount a car fuse 10A at source batt for safety of your setup
                                • Before you go life - insert for initial test a 24V bulb between source batt and FET drain in order to protect your switch in case of malfunction.
                                • Many setups are told to do well if they have a single and heavy connection to earth. So be prepared to check it as well.
                                • The effects expected might arise at certain resonance points of the batteries themselves. The repetition frequencies shall be increased slowly with longer rest after any change. Check for battery behaviour (secondaries)
                                • Batteries are told to discharge first and start charging later on with this new energy. It could be an advantage to use brand new batteries never being charged before with "hot" energy.
                                Last edited by JohnStone; 10-24-2012, 09:00 PM.
                                Experts spend hours a day in order to question their doing while others stopped thinking feeling they were professionals.

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