How to protect OpAmp output?

Hi, I have an OpAmp which controlls the Gate of a MOSFET. When the MOSFET dies, sometimes the voltage it's running on (50V) somehow gets to stand over the OpAmp's output which destroys it. What's the best way to protect the OpAmp from the high voltages that get to stand over the output? Will a zener do the trick? Trigger transformer won't be easy to use here because It's a PWM controller so I need nice block waves. Diode on the output? but won't this be bad for delivering good current to the Gate? ... Any ideas?

Asked by DELETED_Electorials 6 years ago | last reply 6 years ago


What should i do with all of my old hack saw blades?

I have lots of small broken hacksaw blades and I want to do something with them along the line of making weapons or knife attachments or stuff like that!!!  Hope that you all have some good ideas!!! Ps The cut on my thumb is not from a hack saw. I got bitten!!! :2)

Asked by henster22 7 years ago | last reply 7 years ago


Machine that can shape water

The National Maritime Research Institute of Japan has a machine that can create shapes in the water such as hearts and stars. That's just the small one. The larger machine can make much bigger collisions between waves. There's some research around safety here to merit such a large setup, but I'm just happy with the splashes and the over-the-top reactions of the reporters. Always fun to see them shout "sugoi!" and "waaaaaaa!" over and over. via Neatorama research institute Uploaded by hatoyamafandom. - More video blogs and vloggers.

Posted by fungus amungus 8 years ago | last reply 8 years ago


How to create linear motion from non-sinusoidal angular rotation? Answered

Sorry, I coudln't think of an intelligent way of snap-shotting my question. Here's the deal, I have this lab test tube rocker, which oscillates the platform back and forth like a see-saw. It works just like a piston engine, with an electric motor that has something like a crank, and something like a connecting rod, such that it converts angular motion to linear. You probably know what I'm talking about, but I've attached a photo. Because it oscillates on a sine wave the platform spends an equal amount of time at every phase of the wave. But I want it to spend more time at each end of the oscillation, the peak and the trough, more like a sigmoidal curve. What do you think would be the best (easiest) way to do this? Mechanical or electrical? Mechanical seems cumbersome. Have the pin on the crank "float" (so that it has a variable radius) and then have it follow an elliptical (or sigmoid) track? Or have the crank be toothed gear that turns a track that could be shaped over an elliptical or sigmoidal shape, and have the pin come off the track? That seems unnecessarily complex. The easier option (I think), would be to create a timer/switch so that every 180 degrees of rotation, at the ends of the oscillation, the timer turns the motor off for a second. But I have no idea how to do that.

Asked by marozie 6 years ago | last reply 6 years ago


Noise or Music?

The "Bose" sound system is based on chamber resonance like that of musical instruments. This is the difference between a whistle and a flute. The mouth piece of a trumpet is raw without its additional plumbing. The noise of a piezo-electric sounder is raw, but chambered to resonate...better. A trumpet is basically an acoustical waveguide device. Consider this and lets see if you can "WOW!" the crowds with your sounds. The trumpet mellows the sound of the mouth piece by reflecting the sound repetitively off the inside walls of the horn. The angle is low so the acoustic wave reflects many times along the length. What works for you?

Asked by robertgrist 8 years ago | last reply 8 years ago


Export integer from arduino to processing?

How can I take an integer or float value from an arduino, and put it into processing over serial (usb), without changing it to a char or something else?  It needs to be fairly fast (within ~1/8 sec), and be able to be converted to an audio tone.  Also, how can I play an audio tone in processing?  I looked on the reference page, and couldn't find any documentation on just a basic square or sine wave output of variable frequency (except the example, which uses something weird). 

Asked by jduffy54 6 years ago | last reply 6 years ago


Best way to accurately measure capacitance w/ osciloscope?

I am sure there are many ways to measure capacitance w/ an oscilloscope, and one of the annoying things is that some capacitors have different capacitance at different voltages and test frequencies. My original idea was to use the RC time constant and a known resistor, but I think this is probably the least accurate way to do this. Would using a sine wave function generator and figuring out capacitive reactance (and capacitance) be the better method? OR what about measuring resonant frequency of a LC tank circuit? Or some other method I have not mentioned? What's the best?

Asked by -max- 2 years ago | last reply 2 years ago


How to convert a standard video monitor to a pulse-cross monitor?

For video diagnostics, a wave-form monitor and a pulse-cross monitor are highly useful tools. Is there a simple way to convert a standard video monitor into a pulse-cross (sometimes called a cross-pulse) monitor? I.e., feed the signal into a box and the box feeds into a standard video monitor and you can see the normally invisible image corners and invisible vertical interval of the video. I think this can be a simple electronics diagram. Thanks for any help!

Asked by LightSpeed1 4 years ago | last reply 4 years ago


fake magnetic/shaker flashlight to real one?

Hi , I have a fake magnetic flashlight that had lithium batteries. anyway I decided to turn it into the real thing. I wrapped wire around it and replaced the piece of metal inside with strong neodymium magnet. It produces 20 to 100mv when I shake it.I have decided to use 1N5819 diode for full wave rectifier (is it better than 1N4007 ?) . What I need is the proper circuit for charging a 50mAH battery that I am going to use in it. any suggestions would be appreciated :-D

Asked by ehsan_zt 3 years ago | last reply 3 years ago


LED Gloves

I was in a bar tonight and there were these guys with these weird LED gloves and were doing this little show where they wave their hands arounds and it looked really awesome. Seems pretty simple. They have 16 watch size batteries linked up to super bright LEDs. I kinda thought that was a good project to try instead of buying a pair for 100 dollars that are considered quality.  I really don't even know how to go about this.  They're called Light Show Rave Gloves. Here's a video of what they look like afterwords. http://www.youtube.com/watch?v=gwNCnMNs6ww&feature;=player_embedded

Posted by bofthe951 8 years ago | last reply 7 years ago


Waveform Generator

Hi guys! So actually i wanted to make a circuit that can turn on and off an LED array at a particular rate (say 10 seconds time period). I want the LEDs to gradually brighten and dim. At first i thought i can implement it using a multi vibrator, but it it turning off and on too fast, since the output of the MV is a square wave. I want to design a simple circuit that can generate more slowly rising waveform (like sine or triangular) and can also drive a load of at least 100 mA and have a time period of 10 seconds or so. Any suggestions? 

Posted by charmquark 5 years ago | last reply 5 years ago


Pulse width modulation dc motor speed control circuit please !!!!?

Hi friends, I need the circuit of pulse wave modulation speed control. - The motor is PMDC motor. - The input voltage is 12V -  The battery used is a 12V lead acid battery which delivers a current of 35A - Thus the power used would be around 400W (420W to be exact) Please give me the circuit stable enough to withstand this high current.... Note: I also found this circuit. " http://www.eleinmec.com/article.asp?28 " can this circiut withstand my requirements... Thank u ......

Asked by arjun169 6 years ago | last reply 6 years ago


Radio Frequency Proximity Detector

Hello, Does anyone have an instructable for building a proximity detector based on a radio transmitter and receiver? Or some other wave based method? I've viewed the IR proximity detector here on this site, but I need a transmitter/receiver based one. Yes, this is for my pet. I have 2 cats and 1 dog. I need to keep the dog out of the same areas that the cats are allowed to go into, thus the proximity detector needs to be specifically tuned to the dog. Distance does not have to be far, anywhere from several inches to a couple feet. Appreciate any comments or instructables! Thanks, Eric

Posted by riccarr 11 years ago | last reply 7 years ago


Wire bending jigs, does anybody remember some???

I need to make some springs for a recliner. They are the ones that support your back. They look like a sine wave. I have 1/8 inch piano wire, however it is really tough to get bent into the correct shape without a jig. Does anyone out there remember seeing a bending jig on Instructables that had various diameters of bends, etc? The only one I can find is associated with making a NAROD antenna. The piano wire is a lot tougher than the copper used for the antenna. Thanks for any help...

Asked by bucklipe 7 years ago | last reply 7 years ago


how do you program a psp? Answered

 I've been trying to program to psp to access the Ir port. i am trying to make a spy mike it works by making a laser bounce of a window and hit the Ir port of the psp the sound waves vibrate the window creating slight diffrences in the voltage generated by the phototransister now i need to convert that to sond on the psp except i have no idea how to program the psp i dont know anything about c++ but i've been programming in visual basic 2008 for a while now does anybody have any ideas on programs or codes i could use 

Asked by lj123456 8 years ago | last reply 8 years ago


Antenna length for a frequency modulated signal.

I  am given to understand that the length of an antenna is proportional to the wavelength of the signal that is fed to it (a quarter wavelength, for example). In the case of a signal modulated by amplitude, the frequency (and therefore wavelength) of the carrier wave remains unchanged. However, in the case of a signal modulated by frequency, the signal fed to the antenna will vary in frequency (and, therefore, wavelength). My query is this : how would one go about calculating the length of an antenna for a frequency modulated signal? Its frequency is not constant, so to construct an antenna of say, a quarter of the wavelength, would be impossible. I thank you in advance for your assistance. AlexHalford

Asked by alexhalford 8 years ago | last reply 8 years ago


How can I reduce AC ripple current in a power supply? Answered

Hello. I have a 40 amp, full wave bridge rectifier DC power supply that I would like use for radio equipment. At the moment this is not possible because there is too much AC ripple on the DC side. I know that using some form of capacitor you can make a conditioner, but I am not technical enough to know what capacitor to use. Basically I'm asking what I need to do to cut the AC ripple. Thank you very much :) 

Asked by ckgarside 3 years ago | last reply 3 years ago


I lost my glasses in the ocean; help me choose a new pair!

I lost my glasses kitesurfing in some enormous waves at Waddell Creek yesterday! I went through the complete spin-cycle: caught in a wave, spun so fast underwater I didn't know which way was up, almost run out of breath, lose glasses, etc... I forgot to write my email address on them, so if you find a pair of glasses somewhere along the Northern California coast let me know! I've worn my glasses in the ocean for more than 6 years without incident; in fact, I lost so many pairs of contacts to the ocean, that I started favoring my glasses. Below you can see me just coming back to shore wearing my glasses -- on this particular day, I was so tired after 6 hours of kitesurfing that I couldn't get the food into my mouth properly. I choose that pair by wandering into an optical store and demanding "1960's NASA engineer glasses." They were probably more "graphic designer" glasses, but cool nonetheless. Help me choose what I should get next! I'm partial to http://www.optical4less.com/ because they're super cheap and believe me when I tell them "my prescription really hasn't changed and I don't need another eye exam."

Posted by ewilhelm 11 years ago | last reply 9 years ago


Giant Knit Animals Storm CHA

Our friends at Lion Brand Yarns recently suffered a collective wave of gigantism when they set about designing this Winter's offering for the Craft and Hobby Association.  What may have started as a collection of delicately detailed stuffed animals has grown to monstrous proportions.  (Monstrously adorable that is!) Scroll through their flickr stream so you can get a fair idea of the full scale of these creatures.  And if that's not enough, come see them in person at this year's Maker Faire! While you're checking out these amazing creations, get your inspiration on for our upcoming Critters Contest with Lion Brand.   Ladies and gentlemen, start your needles!

Posted by scoochmaroo 8 years ago | last reply 8 years ago


How can I replace a single wire with an infrared link?

I just want to have a digital communication interface become infrared. I have data going both directions, so I need to have the system be two-way. If possible, I would prefer using radio of some sort. For infrared, would it be as simple as an IR LED and NPN phototransistor at each end? EDIT: Bad news. The system needs 2 wires to transfer data. Since IR would mix together, I need to use 2 different radio frequencies. Does anyone know how to send and receive simple pulses of radio waves?

Asked by 4lifenerdfighter 6 years ago | last reply 6 years ago


How can I motivate lazy club members? Answered

I'm president of a club at my college. For the most part we just sit around at watch cartoons but as a college club there are certain things we have to do. Like raise money for charity. If we don't do these things, we lose our club accreditation. Most of the members do nothing to help out, even when I wave the threat of no longer being a club above them. They want all sorts of benefits and extras and things but are unwilling to put forth the time to earn them. How can I get these lazy students to care about the club and help out?

Asked by Captain Zesh 9 years ago | last reply 9 years ago


How do i make an arduino-based Ondes Martenot?

I know only a few basics of the ondes, mainly that it works by having a metal ring disrupt radio waves to generate sound. I have only found one instructable and it is only loosely based on the ondes. Also, I need it to be based on the arduino, because it is the only platform I am used to/comfortable with (other than calc prgms) and many other people prefer it as well. Radiohead fans, Jonny Greenwood uses this in songs including Dollars and Cents (live) and Where I End and You Begin.

Asked by szechuan53 9 years ago | last reply 9 years ago


DIY EEG see whats on your mind - Any Ideas on how to build one?

A Electroencephalography (eeg) is a divice that measure electrical signals from the brain. There is a site called http://openeeg.sourceforge.net/doc/index.html which has plans, but its hard to follow. Wanted to see if anyone was intrested in putting together a instructables to make one of these on the cheap and easy to build. Think this starwars toy could be a starting place? http://bit.ly/71mzRi  It's called Force trainer and I guess it's suppose to read your brain waves. Sound like a load of crap to me, but might be a place to start.  

Asked by JoeMurphy 9 years ago | last reply 8 years ago


Nerf Longshot. Need Serious help please!!!!!!!!!!!!!!!!! Answered

i was moding my nerf longshot and the o ring from the plunger chamber in the longshot went missing. searched everywhere to find it but it didn't show up. the only o-ring i have fits pritty well but it is a bit too fat. i was able to cock the gun but the o-ring is too tight on the side of the chamber. it doesn't want to shoot when i pull the triger. i don't know how to fix the o-ring. can someone tell me if there is a way of shrining the o-ring so it will fit better. or perhaps a mod on the piece that the o-ring goes onto. Please Help!!

Asked by shadow wave rider 7 years ago | last reply 7 years ago


SSTC Trouble Shooting?

I am in the prosses of building steve wards Class E SSTC( http://stevehv.4hv.org/classEsstc.htm )and copyed the secondary from here: ( http://www.richieburnett.co.uk/hfsstc.html ), i have it all set out i am am using all the componants he does only mine does not work(not that I expected it to work!). i do not have acsess to a osiliscope nly a multi meter with the Hz function so i can not look at the wave forms it the Gate/ anntenna. Any help would be much appresiated as i have not really worked with tesla coils/ resonance before.

Asked by MadScientist101 7 years ago | last reply 7 years ago


Am I using this guitar humidifier correctly? Answered

I recently acquired this Planet Waves Acoustic Guitar Humidifier, and on the package it says no leaks because the holes are on the side. I can only store my guitar (in its case) on its side, so one side is facing downwards. I am putting in the minimum recommended water amount, but i am still worried it will leak. Will it leak? Will I have to store the case laying flat? I really don't want my new acoustic to crack or warp, but i also don't want it to collect water, as this will mess up the wood. Please help!!!

Asked by freeza36 7 years ago | last reply 7 years ago


How to wind a flyback converter to use with HHO generator?

I have an electrode made of 304 SS that when hooked to a 12V automotive battery draws about 80A. That is WAY too much amps, and I want to boost the output voltage to 36 or more, and reduce the amps as low as possible. I plan to drive the flyback with a square wave generator. What do I need to know to wind my own coil: what core, size of wire for primary and secondary and how many turns of each? Thanks in advance. I've already found that an ignition coil will not work, unless you know of some way to adapt one so that it will.

Asked by galveston 9 years ago | last reply 8 years ago


I need a way of measuring a 0-1000kHz signal (50% duty cycle square wave from a TSL237) with an arduino. Answered

I'm willing to use external hardware if it is cheap.I've tried using an interrupt base pulse accumulator but when the frequency becomes high the counter increments so fast that it stops the arduino from doing anything else (like stopping counting). Does anyone know of a nice easy solution to count frequency? Perhaps a fancy 8 pin DIP that talks i2c? I need to be senstive to the very low end of the frequency scale too, so just throwing a prescaler on will not solve this (afaik). Thanks.

Asked by quatch 6 years ago | last reply 6 years ago


HEAT: A Fire Cabaret

If you haven't heard yet, The Crucible's annual summer homage to fire is moving indoors this year, transforming their industrial arts studios into a searing jazz-age underground speakeasy where fantasy and fire converge with sultry music and machinery.  Some of the best talent in the Bay Area will perform amidst artisans plying their fiery trades, and guests will be invited to explore an industrial speakeasy alight with furnaces, forges and flames.  Time to get started on getting all dolled up for the 1920's -- think flapper dresses, finger waves, tommy guns and bootlegged fire.  More info and tix at: www.thecrucible.org

Posted by plasmajan 8 years ago | last reply 8 years ago


Effectiveness of sugar as a piezoelectric material

Most of the sites discussing piezoelectricity mention that sugar crystals can be used, but I have not found any examples of them being used. I've just tried it with about a 1cm chunk of low quality (conglomerate of small ~3mm crystals) crystal, and got a good 100mV wave when tapped with a pencil. I've not tried applying a signal to it yet, and some better single crystals are growing at the moment, so I was wondering how well it works compared to commercial piezoelectric compounds. I've not done anything like this before, so if anyone knows where I can find information of the best way to mount and apply a signal to the crystal, it would be appreciated. Thanks in advance.

Posted by The Skinnerz 7 years ago | last reply 7 years ago


Is Arduino can do FM modulation? Answered

Is Arduino can do FM modulation without any additional peripherals.Simply an Higher AC frequency signal with antenna can propagate in air. My question is,can we do FM modulation in Arduino only by coding it,without using any additional peripherals.Generating the carrier frequency in Arduino by coding it and then by performing FM modulation by coding it,getting the external audio signal through Analog input pins and after all the modulation process, connecting a long wire on the digital pin of arduino because the square wave is going to be used as carrier signal.A simple wire can act as a Antenna.Is the above explained process is possible in Arduino only by programming it.

Asked by Rajkumar2506 1 year ago | last reply 1 year ago


How to Identify or Measure Inductance?

I am gathering the parts for an ible, but I am short one part: a 12mH inductor.I can spot some inductors in electronic garbage - the wire coiled around a ferrite loop - but there are also solid state inductors. Plus, the inductors are not usually labelled with their values.How can I measure the inductance of an inductor with a volt-meter and an ammeter, but without access to a sine-wave generator?Is there some simple trick that would get me "close enough" to the true value? What would be really useful (but probably doesn't exist) is a chart or formula where you plug in the size of the core and the number of turns around it and out pops the inductance value. ?

Posted by Kiteman 10 years ago | last reply 5 years ago


CAR WAVE-CONGESTION AVOIDED BY WATCHING YOUR "SIX"

Historians traditionally tell us that to ignore history is to repeat its pitfalls. So how can history help us improve the flow of car traffic? Did you know that many aspects of the world’s legal systems come from biblical origins using tried and true fundamental laws originating from the Ten Commandments? The concept of “watching your six” borrows from these universally accepted laws, whose credo stipulates guidelines for human interaction as well as interaction with god. Your "six" refers to the driver behind you whom you should treat as you would yourself. With this in mind, we have a new credo for today’s need to interact with each other by driving your car responsibly through high density traffic to avoid “wave congestion". This term is used to describe isolated packs of cars suddenly causing a local slow-down in traffic flow, while both upstream and downstream traffic continues to still move well, and so our rule states:   “Drivers are responsible for the immediate driver behind them, keeping him safe and avoiding unnecessary braking”    How This Rule Works In traffic: 1)            The Rule is Expansive, All Inclusive and Saves Us Money If we followed this general rule, we would become responsible for leaving the proper space/time ahead of the car in front of us. Space clearly gives us reasonable reaction time to perhaps "brake by simply coasting" and not force the driver behind us to suddenly brake hard. It will help us to recognize that the proper spacing between cars is not an open invitation to dart between lanes just to get ahead by one car length. This causes “wave congestion” and the possibility of accidents during heavy traffic situations. It assures that braking is something one does as a "last resort" and only when no other circumstance for safety and/or avoiding a collision is available. It holds the “rubber-necker” responsible for maintaining good traffic flow or get ticketed. The rule encourages a driver to adapt the techniques of defensive driving so as to avoid accidents, and to embrace the proper social skills of driver etiquette to mitigate road rage and its associated erratic driving behavior. Ultimately, the rule will financially help us to reduce our car insurance costs by promoting fewer negligence accidents. 2)            Eliminate Reactive Braking … Trust the Driver In Front of You Keep in mind what normally happens in heavy traffic when the first driver uses their brakes either in idle thoughtlessness or in protective response to traffic congestion ahead. Under these circumstances, we reactively use our brakes for two reasons:  a)   Reduced Reaction Time  - The first car’s brake lights go on, giving us less time to react so we over compensate by braking harder than him. This affect gets compounded, causing each subsequent upstream driver to brake still harder, until the reactive braking time becomes impossible to respond to and a collision or multiple collisions occur.  b)   We Don’t Trust Other Drivers  -  We are conditioned not to trust our fellow drivers because they haven’t yet been educated to abide by our Rule. This lack of trust causes us to drive "overly" cautious and results in the over use of our brakes to defend ourselves. Our driving habits have created a psychological situation just waiting for an accident. 3)            Implies Driving Etiquette that Must Become Required Driver’s Education The rule and its derivatives must be taught as part of our driver’s education program, and their concepts definitely reviewed during the licensing exam. The Rule also includes adherence to a driver’s code of etiquette which goes beyond just obeying our basic traffic laws of vehicle safety as is currently done. Highways are becoming too congested to allow rouge drivers to ignore their “social” driving responsibilities and the etiquette of the road.  Traffic tickets for abusing social driving etiquette should be as prolific and costly as our traffic laws for speeding and/or not stopping at a stop sign, etc. 4)            Compliments Our Near Term Use of Self-Controlled Vehicles Our Rule intrinsically implies the responsibility for social driving etiquette and takes us forward with steps that avoid future traffic congestion.  Improvements will come from technological automation which will eventually take the erratic human factor out of our equation to produce the smooth flow of traffic even during congested periods. Something as simple as today’s cruise control helps us to avoid “wave congestion” by maintaining a constant highway speed plus reducing inadvertent “brake riding” which sends the wrong message to the driver behind us.  Our ultimate step towards smooth traffic flow involves using near-term technology that completely eliminates drivers and relies on self-controlled vehicles taking over within regions of high density traffic. Ideally this will eliminate traffic accidents due to the unpredictability of driver shortcomings, making technological glitches our only possible area of concern in the near future. Google, in cooperation with the state of California, is currently in the process of introducing such vehicles onto the state’s roadways.

Posted by RT-101 6 years ago


Input problem with OpAmp-controlled ZVS Induction Heater

Hello, Idea: I'm trying to build a circuit which uses an OpAmp to drive 2 mosfets, which power the LC tank of an induction heater. The idea is to detect when the voltage over the LC tank crosses zero, and at that voltage I would make the 2 outputs of the OpAmp change states from fully on, to fully off. The two OpAmps (both inside one chip) have their positive and negative inputs connected to eachother, but with reversed polarity. This would make sure that one output is high, and the other one is low. Why use an OpAmp? I wanted the MOSFET gate switching to go faster as usually, because in the mazzilli circuit, the gate voltage actually slews at the same rate as the LC tank's voltage slews when it crosses zero volts. In the mazzilli circuit, it actually doesn't switch when the voltage is 0v, but when the tank voltage drops below the gate threshold voltage. This would mean that you are always switching current at 5v (for example) instead of at 0V. So for these two reasons, I wanted to try switching them with an OpAmp. Measurements: Probe I on drain 1, probe II on drain 2, and GND on the circuit's ground, gives me an expected result: when switching states, at 0 voltage of the LC tank, the voltage on one side stays low (since it's pulled to ground) and the voltage on the other side goes from 0v up to 50v, back down to 0v, like a sine-wave. Then the OpAmps switch again, and the one side now goes up to 50v as a sine wave, and the other one stays low at 0v. All good, this is working just fine. Probe I on the one differential input line, probe II on the other differential input line. Since this is nothing more than just a 1/10 voltage division of the previous measurement, I'm also expecting the signal to be exactly the same, but 11x smaller. -> problem: However, this does not happen. Because of some strange reason, as you can see in the scope images: Both channels go high, Twice per cycle, instead of going high only once per cycle, and staying low for the next half of the cycle. This really isn't good! Do the inputs affect the waveform in some way? Remarks about scope images: Image: 2 gates Blue gate voltage seems 'quite' fine. Turning on looks good, turning off is not really good becuse if tends to turn on for a short time once again, before it fully turns off. Yellow gate voltage is terrible. Turning on doesn't happen as expected. Voltage drops back to 0 for a long while which is very bad for the circuit. Frequency seems fine; 50kHz is as expected with the 14µH and 6µF. Image: 2 drain voltages These voltages were measured with a 1-10 voltage divider, and thus show only 1/11th of the actual voltage. This is getting close to what I want the LC tank to do. The voltages seem quite like sine waves. I suspect that if the gate voltages would be as they should be, these drain voltages would also be perfect sine waves. The regular sine amplitude of 50V is as expected, with a 24V supply voltage, but at the moments when the drain voltages strangely drop down to 0v, as you can see in image: '2 gates', at these moments the drain voltage seems to spike over 250V!! Image: 2 differential input lines This is the image which I don't understand. I expect the same wave as in the previous picture, but only 11 times smaller because of the voltage divider. However, the voltage does NOT reach 0v while the drain voltage does, and its shape is also completely different. In this image, both channels are doing one (half) sine wave, twice per switching period. They should be LOW for half a period, as the drain voltages do in the previous image. Better quality images: 2 gates 2 drain voltages 2 differential input lines schematic Datasheets: OpAmp: http://cds.linear.com/docs/en/datasheet/1497f.pdf MOSFETS: http://www.vishay.com/docs/91262/91262.pdf Coils and capacitors: Line inductor value: I'm not sure if this value is correct. Center-tapped main coil inductance: This value should be pretty correct, I calculated it by measuring it's size and windings, and the operating frequency is also nearly the same as the calculated one. tank capacitance: 6 times a 1µf MKP capacitor Questions: - Why these strange large spikes? - Why is the waveform suddenly different when reading it near the differential inputs? For the first time ever, I can provide you with scope images! I finally bought a (quite cheap) oscilloscope. I hope it helps a lot. Oh, and one more thing: The induction heater does actually work already. I'm getting huge currents in the LC tank, since the 6mm copper tubing gets hot after a minute. Water cooling has been added, and it works like a charm! The MOSFETS do get quite hot after 15 seconds of heating an object, or after 40 seconds of heating nothing. This, probably because the gate voltage isn't what it should be. Kind regards, Electorials

Asked by DELETED_Electorials 4 years ago | last reply 4 years ago


Hydrofoil Surfing - A New Adrenalin Sport

Listening to Silvio Rivier, the host of Global Village, there was a section on Hydrofoil Surfing. I turned to the television, interested by this large word, to see this guy surfing a foot above the water! It seems that instead of floating along the water like a normal surfboard this board actually would be below the water while you stand on it. A jet ski pulls the surfer up to speed, bringing him up to the top of the water, but that's not it, there's a fin that leads down a foot and a half or so below the board, and attached to the end of that is a special shaped piece of metal called a hydrofoil that collects the water as it comes up from the bottom of the sea and goes over as a wave. The surfer then keeps going upwards, until the "foil" is about 4 inches under the water. Therefore the surfer can balance above the water, with very little resistance & going very fast. It's technically possible that this could be used for surfing not just close to land, but hundreds of miles out, so the person can surf for as long as their legs hold out, because they can surf in rougher water. Does any body think they could build one of these? Balancing on one is supposed to be like using a uni-cycle, & I'm having trouble surfing normally so even if I did build this I probably couldn't ride it. This goes out to Laird Hamilton, the creator of this funky board, & I'm looking forward to an Instructable. Cheers everybody, ~K P.S. The links aren't working so I'll add them as soon as possible. Neither is the video button, sorry about that, I'll have to add a picture instead.

Posted by Kryptonite 9 years ago | last reply 9 years ago


Arduino Outdoor Security System - PIR Motion Sensor, Security Lights, Intruder Warning/Alarm & Blynk Notification

I would like to ask your suggestions on how to build an outdoor ESP2866 security and sensors combo. I have seen separate postings on PIR and lights around the site and in other websites so I thought it would be doable. I knew Arduino then but only paid close attention when I realized that my x-10s are outmoded but z-wave devices are expensive. So I am learning about it, how to sketch and trying to understand C++ more. My dream is to build an outdoor ESP2866 combo, powered by an AC120v-5v module, with two PIR motion sensors, three 120v relay switches (two relays for two sets of security floodlights and one relay for an amp/wave speaker with mic), a photo (dusk/dawn) sensor and temperature/humidity sensor (for a future thermostat). Operationally, I imagine that it could be armed and disarmed through Blynk. When armed at daytime, a motion will trigger a low volume intruder MP3 warning alert with 10 minutes of security lights at night. But if the trigger persists for more than 5 minutes, the security floodlights will blink, a loud intruder alarm will sound and push phone notifications. What will be the best way to sketch these? What is the better way of wiring them together? How could I make multiple ESP2866s in the same WAN work together for an event? The desired function is if an alarm event is triggered in one of the ESP2866 that would also set off blinking lights and alarm sounds in the other ESPs. Thanks for all your help.

Posted by EeA2 1 year ago | last reply 16 days ago


Is it possible to hack an AM transmitter that transmits at about 1500KHZ to be used as a cellphone jammer?

I know that the band for cell phones is between about 800-1990MHZ and I was wondering if it would be possible to hack an AM transmitter or for that matter an FM ipod type transmitter into the cell phone range like KipKay did in his instructable with a reciever so that if you transmit noise it would disrupt the cell phone call and make them hang up. This is just an idea I had that would be the alternative to creating a jammer like the Wave Bubble made by Lady Ada that would be a lot easier and cheaper. This is not intended for bad purposes, its just for fun. I might not even make it but I am still wondering if it would work.

Asked by beak90 9 years ago | last reply 9 years ago


The Crucible's Fire Cabaret

If you're going to this wild and wicked event, and you want to dress to kill, check out some ideas (and get tickets) here:  The Crucible's Fire Cabaret There are some other good ideas here on Instructables, too, for flapper dresses, tommy guns, how to do a finger wave, or headress.  This is gonna be one hot event -- you'll see some hot jazz and blues, and also jaw-dropping demonstrations in blacksmithing, welding, flameworking, and more -- accompanied by burlesque dancers, aerialists, contortionists, and other amazing talent.  Bring a camera too and strike a pose against a backdrop of fire sculptures, bootlegger cars, and a blazing industrialist environment.

Posted by plasmajan 8 years ago | last reply 8 years ago


Premonition?

Last night I dreamed of massive Earthly destruction by huge flaming rocks from the sky. It was really, really cool, but rather scary. Black sky, massive and multiple flaming rocks from above impacting with devastating effect (some distance away, but close enough to feel shock-waves). Not like the image, more real and hot-burning coals like (but that's the best I could manage to get for 2 mins of searching)If it happens soon it's a premonition?(I also dreamed that some landlord-bast's had been in while I was out and cleaned my place out of all the junk and important stuff like my furniture, PC etc and moved the stuff out of the shed into my lounge, but that was a completely separate scene and in daylight...)I was glad to wake up!

Posted by lemonie 9 years ago | last reply 9 years ago


sound-only area and cancellation

I'm looking for advice. (now this is difficult to explain but I'll try my best) I am trying to design a way to have a dance floor in an open area that will have an area where you can hear the music but away from the area it can't be heard. I'm attempting to do this using an array of speakers around the dance floor that will cancel out the music past the dance floor. Each speaker will face away from the area and be equipped with a microphone (directed torwards the main speaker) that then goes through and amplifier and then to the speaker (wired up so that it will emmit an opposing sound wave). This would essentially create a sound barier. I have attatched a picture as a visual aid.

Posted by Sun Gear 6 years ago


hearing electromagnetic stuff

Well, I was going to plug my ipod into some old computer speakers. my thumb touched the tip of the jack (ground) and it makes a buzzin noise. Big woop. No, as I go to reach my ipod it makes a big buzzing noise. what I was hearing was the electromagnetic waves. I reach for my cell phone and then a loud really highpitched noise ccame out. I waver my hand over my computer's power supply, I here a loud buzzing noise. How to do this: press tip of thumb to tip of 3.5mm jack turn your speakers up pretty high waver hand over complex electronics boy, do i have fun mornings, lol, being sarcastic

Posted by guyfrom7up 10 years ago | last reply 10 years ago


How does one make a simple radio with a transmiter and a receiver? Can someone better explain a passive RFID tag?

I use a fm transmitter and a fm receiver to connect my tv to my computer speakers. The device is not very cost effective and I tried to make my own transmiter and receiver that had one frequency. I then learned about passive RFID tags and wondered how it could both transmit and receive a radio wave. And it only uses a memory source with an antenna in the form of an inductor. I began to wonder if I could make a tranmiter and receiver like an RFID tag. There is so much about radios in general that I still can't comprehend.

Asked by mcguyverzboss 9 years ago | last reply 9 years ago


Help me selecting antenna for my fm transmitter????

I am building fm transmitter i am finished with every thing in circuit leaving antenna i searched for d.i.y. antennas but there were many confusing names of antennas i dont want to go through all those defination, uses ,advantages etc. of those antennas so please help me choose. I am adding a image of my circuit please help me choose from dipole, 1/4 wave ground etc. antennas. It will be nice if u tell me any d.i.y. to make your suggested antenna. Remember i want my transmitter to work from 88-108 Mhz

Asked by Atul009 5 years ago | last reply 5 years ago


Trying to convert a mains powered string of LED's

Hi, I purchased a set of Xmas lights believing them to be 'low voltage'.  My plan was to run them from the caravan 12 volt DC.  However, it appears that they run from the 230 volt AC mains.  This is something I am not familiar with. I have attached my own wiring diagram of the circuit and would like to know if anyone can tell me how to switch the four strings of LED's individually.  I have an inverter that I can use as the current draw will be minimal. I imaging that the LED's are wired as opposing pairs so that both halves of the mains sine wave are used.  Presumably, this prevents the set being run from 12 volts. Any help will be welcomed. Alan ...

Asked by newalfi 4 years ago | last reply 4 years ago


HAARP mind control?

Allegations have been made that the HAARP project is behind mind control experiments. The ex governor Jesse Ventura, interviewed a professor who demonstrated in his show that it is possible to send messages to people's minds without any need for hearing. The professor put two piezoelectric transducers on Ventura's chin and Ventura claimed to be able to "hear" music in his brain. Real science or pseudoscience? If this device could be made, wouldn't this device help people without hearing? What about the possibilities of learning devices or communication? I believe that this device could put thoughts on people's minds but not necessarily control them (unless it is an easy suggestible subject). Please watch a segment of the show and share your opinion:

Posted by blkhawk 6 years ago | last reply 6 years ago


Hey all ! anyone miss me? :-) ....

I can't stay for long, but wanted to bring you all up to date.... #1: I have been really busy with a couple of Asperger Forums and my own support group.. Over the weekend, while cleaning up, I started getting pains in the lower gut.  After it didn't go away in 5 hours, I dropped by the ER.  A CT scan indicated a new hernia, lower down and that the bladder was pushing itself into the hernia..   There is now a kind of a rush to get this fixed before the end of the year (deductibles and all)   Thought I would stop by quickly tonight and say HI !   And I hope you all are doing well. 

Posted by Goodhart 5 years ago | last reply 4 years ago


Can I use an RFID reader and card to activate lights?

I was thinking of putting some string lights around the top edges of my room. Near the entrance, I want to wall mount an RFID reader in an enclosure so that when I wave the card in front of it, the lights would toggle on or off. I was also considering putting a second reader near my bed so that at night I could turn the lights off while sitting in bed. I would really like some help on how to do this because I don't have a clue on how to allow the reader to control the lights. Also, the lights will probably be ones that plug into a normal outlet, just in case anybody was wondering.

Asked by xlivewire7x 9 years ago | last reply 9 years ago


Pulse detonation(numerical simulation)

Hello everyone iam a Msc student now, i have done many projects over pulsejet engines which you could see in my instructables list. Now i have decided to do a project over pulse detonation engines, before beginning with the real one i thought that making a fluent simulation will be better. I have several tries to create the detonation front and atlast i succeeded in creating one. Take a look at the attached pictures which shows the development of a detonation front inside a long tube of 100cm. Further works will be updated soon. Want to see the sequence of deto wave formation please follow the link... http://www.4shared.com/archive/a4unsF-9/sequence1tar.html?

Posted by ganuganu 5 years ago | last reply 5 years ago


the speaker on my iHome is squealing. MAKE IT STOP!?

I recently acquired an ihome from a friend. the reason he gave it to me (like so many others) is because I am fairly handy and people know I can fix stuff, and this particular device emitted an irritating squeal. when you turn it on, it has a (fairly loud) high-pitched squeal that sounds not unlike a simple square wave. it doesn't really fluctuate, it just squeals. it doesn't go away when the volume goes down, and when you play music it seems to intensify. does anyone know what could be causing this, and how I could get it to go away? (if all else fails I might try adding an inductor to block the high frequencies.)

Asked by codongolev 5 years ago | last reply 5 years ago


Half bridge in "A reliable plasma speaker doesn't work"?

Hi! I am a  student and I just started to make my first half-bridge plasma speaker, and I used the schemetic in https://www.instructables.com/id/A-reliable-plasma-speaker/ However, after I finished, it didn't work. I used an oscilloscope and I found the VGS of high side MOSFET was between -3 and -6, and the low side was between 12 and 0. Then I accidentally got it work, but the MOSFETs were very hot, and then they exploded. After I change the MOSFETS, it had the same problem as before again. But if I short the capacitors, the wave form for both the high and the low were correct. can anybody explain why? Thanks.

Asked by carldong 6 years ago | last reply 6 years ago