NPN to PNP control? Answered

So as I get into this project the circuit keeps building and now I once again have another problem that I can't figure out. As the title hopefully suggests I am using a NPN PN2222A trans. to control a PNP 2N3906 The idea was to use the 5v from a Ardinuo UNO to control a 12v. Currently I am testing with a 9v I had on hand. I thought it would pretty straight forward but every time I supply power to the NPN it creates the short needed to turn on the LED, but once I cut the power the LED stays on until I create another short (using a probe) uphill of the NPN. The only thing I can think of is that the LED doesn't the resistance needed for the power to re-saturated the PNP. Any thoughts? I will admit  haven't done any of the math needed yet for the resistors. Also can someone send me a link to the programs you use for drawing the layouts so I can move past MSpaint?

Question by Jayccob   |  last reply


Do they make PNP Transistors that can handle 3.3A

Do they make PNP Transistors that can handle 3.3A

Topic by kendallickes   |  last reply


What practical applications do PNP and NPN transistors have? Answered

I read about NPN and PNP transistors and I was wondering what type of applications are right for each type of transistors. I understand that depending on the type of transistor the emitter should be connected to either an anode or cathode.

Question by blkhawk   |  last reply


Transistor question

Hey guys I have a question on transistors. When using for PWM setups, is the difference between each NPN (or PNP) transistor model by its specs? Such as gate voltage, max current, etc. I am making a LED touch setup made by qs, but I want to make it so that the Arduino activates a transistor to turn on a string of lights that the arduino could not power on its own. Here is the setup of the LED string. I want to replace the TIP31 in the wiring diagram with a NPN transistor (like this one). By replacing it, which pins go to which wire and do it have to add anything else to the setup? Will the new setup also work with PWM signals? Thanks! KT Gadget

Topic by KT Gadget   |  last reply


Can I make a joule thief with Pnp transistor?

I  was making my joule thief recently and I could not get success. I found out that I have Pnp transistors and that's why I am wiring them wrong. Can anyone provide me with a schematic to make it with Pnp transistor?  Thanks for your help!!

Question by aninda13   |  last reply


Transistor H-bridges

Is it possible to make a transistor H-bridge with PNP transistors or can it only be done with NPN transistors.  As far as my knowledge( or lack thereof) of transistors goes, I think it would be possible, but it would require more than 4 transistors and it would be much more complex, however I could be entirely wrong.  Any input would be helpful, thanks.

Question by jpenn   |  last reply


Need help with JFET preamp and chossing transistor ? Answered

Hello .I'm having some some problems with my current project .Can you guys help me please ! This is the schematic of MXR headphone amp for guitar .I don't have 2n4401 and 2n4403 , so i replace them with 2n3904 and 2n3906.The result is output is too low .2n4401 and 2n4403 (collector current = 600mA) ,2n3904 and 2n3906 (collector current = 200mA).If i replace the transistor with higher Ic i will have louder output ??? http://i247.photobucket.com/albums/gg132/chipmapple/mxrheadphoneampschematic.gif Thanks for advance! Sorry for my bad English!

Question by login721   |  last reply


How do i know if a transistor is npn or pnp????

How do i know if a transistor is npn or pnp???? plz HELP

Question by Dannne11   |  last reply


help picking transistor

Me no get no transistors. me need help. me using ltc4060 chip and me need help picking the pnp transistor. heres datasheethttp://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1037,C1078,C1088,P7601,D5235it's on page 14 - 15I'm using 3 cells and a charge current of 35 mABTW I'm not stupid, just never really got how to use transistors

Topic by guyfrom7up   |  last reply


What or which PNP Complementary transistor can I use with a N-Channel IGBT HGTP10N120BN 35A 1200V NPT Transistor ?

What or which PNP Complementary transistor can I use with a N-Channel IGBT HGTP10N120BN 35A 1200V NPT Transistor ? I can't find a 1200v PNP transistor. Ed.

Question by DELETED_applegoose   |  last reply


information required about "NEC D882 PNP-transistor"?

I need help and instructinos about "NEC D882 PNP-transistor" i want to use it in lamp ballast.. tell me the other equivelent transistor.... the maximum volt and current we can give to these transistors.... thanks

Question by bilalinpk   |  last reply


How do i know if a transistor is of PNP or NPN type?

I want to know how to recognize the type of transistor.

Question by bishal   |  last reply


does anyone have a circuit like this? Answered

I am looking for a very simple audio amplifier circuit that uses a PNP Darlington transistor. it only has to be a couple of watts. the only thing i could find online is a 1 watt amp using an NPN. i would prefer it runs on a 9v but 5v from an L7805 is good too. the least amount of components required the better. 

Question by fossilshark   |  last reply


Complementary transistors

What or which PNP Complementary transistor can I use with a N-Channel  IGBT HGTP10N120BN 35A 1200V NPT   Transistor  ? I really will thank you . I'm building an H- Bridge motor drive. Ed.

Topic by DELETED_applegoose   |  last reply


How Do I Make LED's Fade with an already build flashing circuit? Answered

Hello everyone! In my spare time I've built a simple circuit which makes an LED flash. The flashing is controllable through a Potentiometer. I have attached a circuit diagram (made really fast, so i know it's bad) and the picture of the breadboard. Now, my question is: How can I make the LED fade on and off instead of flashing? I've tried to hook up a transistor but i've not succeeded. If everyone could help, I'd appreciate it. Here is the stuff I think could be useful that I have avilewable: Some BC 144 Transistors (I suppose they're PNP) Some PN 2222a Transistors 220uF Cap, 100uF Cap and a 10uF Capacitor. A lot of resistors. I do have more components but I don't think they could be used for this project. And excuse me for any mistakes, English is not my Language, Thank you!

Question by Reogen   |  last reply


Battery Charging Light Circuit

Dear All I am building a small scale PV system and I want to implement a circuit that will allow a LED to light up when the battery is being charged from the PV cells Currently I have a general purpose PNP transistor with a 2KOhm resistor for the base and a 1KOhm resistor in series with the LED, however when running this simulation the LED will not light, even when I lower the values of the resistors Any help would be much appreciated 

Topic by EmptyCoffin92   |  last reply


Quick Transistor question?

I am using pnp transistors as switches. I finally got a working prototype!!!Anyway my prototype motor runs at .18A and the real motors I want to run are 3.3ACan these PNP's handle that?http://www.radioshack.com/product/index.jsp?productId=2062585And can you tell me how to figure that out so I'm not always asking simple questions?Thanks!

Topic by kendallickes   |  last reply


I need help with short circuit detector / electronic fuse. Answered

So I'm making a variable power supply with an LM317 and I've decided to add a short circuit protection, I know the LM317 has an auto shutdown feature but I thought this would be a nice feature and it would allow me to leanr more about circuits. The short detector is quite simple, It's a PNP transstor connected to the output. When the output is shorted the LM317 can't supply enough current and the load sucks everything it can, so it sucks the charge of the capacitor, causing the PNP transistor to activate and turn on the relay and the LED. This connects the PNP to ground, making it be permanently oopen until the circuit gets reset. It works flawlessly from 16 to ~9 volts, but I go under ~9v (I don't know why) the PNP activates and the relay flickers very fast, I tried several things but none fixed the problem. I have plenty of PNP nad NPN transistors so if you can come with a better and more stable design I would be able to try it, I'll be all the afternoon trying if I can figure this out and posting some updates. Here's a video of how I want it to work. https://www.youtube.com/watch?v=1nVzUUYPm3w& Look at the image for more information. Thanks in advance.

Question by Victor805   |  last reply


Can a 2N3055 transistor be operated at voltages under 60v ? Answered

Can the minimum collector emiter sustaining voltage of a transistor be more than the power supply voltage or is that somthing else? For example can I run a transistor with a minimum collector emmiter sustaining voltage of 100 with a 12 volt power supply ? Thanks

Question by build a BOOM   |  last reply


what can i do with this?

I have a chip off of a mother board here and i was wondering wht can i use it for. it is an award (company name) 1998 pci/pnp 686 216816591

Topic by fretmelter   |  last reply


stop 7-segment from ghosting?

I'm working on a simple arduino 7 segment driving circuit. (It also has a led bar-graph that displays binary numbers but that part is working fine.) When I get the display working I might make an instructible out of it. Here's the basic layout: -using this 8 segmet 4 digit common cathode display. -arduino controls what segments are on via 74HC164 8-bit Serial Shift Register -shift register controls an array of 8 PNP transistors with base and pull-up resistors -transistors connect to display anodes through resistor array -display cathodes (common for each digit) connected to array of 4 PNP transistors with base and pull-down resistors  -PNP transistors controlled by arduino. (I will post the schematic shortly.) In software, to display a four digit number, I shift the pattern for a given digit to the shift-register, which in turn turns on the PNPs for the corresponding segment anodes. I then turn on the NPN for that digit's cathode. I delay for a few milliseconds, then turn the NPN off, shift the next digit in, and turn the NPN for that digit on. Rinse and repeat. It works fine but the segments that should be off are at about 1/2 brightness, making all the digits look like eights. Even the DP looks like it's on and I'm not turning it on anywhere. Do I need pull-down resistors for the anodes or something? What's going on here?

Question by Vick Jr   |  last reply


Can i make a LED to fade with music?

I want to have a LED alwais on and with the tempo of the music the LED will turn off or fade. to make this i have a npn a pnp and a SINGLE OPERATIONAL AMPLIFIER the led is 3v. i don't have an Arduino o another tipe or controller

Question by clowreed   |  last reply


what is this transistor?

I found this transistor in an old genius ps2 mouse (the connection not play station!) it looks like any normal one i've searched google and data sheets searching for it nothing came with any information (one of them said this is a DC motor!) written on it: 536 f   1A exactly. so is it npn or pnp is it power,audio,or general purpose

Question by top.boy   |  last reply


Will this 'switching' circuit work for cabinet lights? Any comments?

Im making cabinet lights using LEDs. I use a transformer to power it off AC mains, but I want it to run on batteries too... So Im making a circuit that would automatically change the source of the power from the mains to battery when the power goes out, and back again when it comes on. Im using an NPN and a PNP transistor to do the switching. When mains (S1) is on, the NPN is on and current flows from the transformer, when S1 is off, NPN is off and PNP is on and current flows from the batteries. What I am worried about is that (I think) the transistors need a Gnd on the emitter. Is that right? If I connect the +ve of LEDs to [OUT] and -ve to GND will it work as expected? Can someone try please?

Question by pro2xy   |  last reply


Solar charger schematic using mppt

I am facing problems with my solar charger circuit using mppt. The main problem is the mosfet switching followed by the dc-dc converter. When i connect my circuit to MSP430 to give PWM at gate voltage drops across the solar panels. I am using a pnp and npn combination to drive the NMOS IRF540. Please help me with the schematic ..

Topic by akash1994jain   |  last reply


Transistors are best for melting brains!!

I have been experimenting with transistors for 3 days now, both NPN and PNP. So far I have concluded nothing. I figure the easiest thing to do is to make a transistor work as a switch. With the NPN, the current seems to flow from the base to the emitter automatically. My understanding is that current should flow from the collector + to the emitter- only when I apply voltage +? to the base, is that correct? I don’t even need to connect the collector on the NPN and current flows. I have also read a million things about transistors online. My experiments seem to disprove most(all?) of the findings. This leads me to one conclusion. I’m not doing something right. Maybe I don’t have the right transistors. I have no idea. I have been using radioshack NPN’s (276-2016) and PNP’s (276-1604) When it tried to make a switch with a PNP my voltages was going back through my emitter to ground. If I disconnected it the system(test led) no longer worked. You might need to know that I was using a 5v voltage regulator to supply a 10v 5v and ground leads for my experiments. I was getting odd voltage readings on my circuits so I put diodes on the leads. The diodes stopped my PNP from working(I figured the current was flowing odd ways…back in the 5v+?) and didn’t seem to effect my NPN experiments. So I figure I’m closer on my NPN’s than my PNP’s. I wish I could explain better but my brain is about to melt. My wife is mad at me because I am obsessed with making this work… please help :P

Topic by kendallickes   |  last reply


How to control more positive current using microcontrollers?

Most microcontrollers can directly control low current  at +5v. Using NPN transistors I can control higher currents, but now negative. My question is: how to switch more positive current (>40mA) than my microcontroller can do directly? The obvious idea is to cascade a PNP to a NPN transistor, but aren't there ICs ready-made for it? More or less like UNL2803A, but using Sziklai arrays instead. What would otherwise be the "standard" way of doing it?

Question by eshneto   |  last reply


I have a large bipolar stepper motor. What's the simplest circuit to drive it with a microcontroller (arduino)?

I have a large stepper motor with 4 wires (bipolar) from an old printer and I assume it's 12 volts, or at least higher than 5v. I have plenty of transistors: 2n3904, 2n2222, 2n4401 and 2n3906 (PNP). How do I drive the stepper with output from an arduino? (simple H-bridge schematic?) Also, how can i find how many steps it has? Thanks!

Question by Vick Jr   |  last reply


Led flasher 555 delay-off help!?

I have a working 555 flasher circuit:  http://www.555-timer-circuits.com/flashing-led.html - i have added a switch between the + and the board, and replaced the R2 with a variable. Works great! Now i would like to add a "delay-off" function, if thats what it is called, so a single activation gives 10 seconds of flashing. So, any advice? PS: I have pnp & npn's, resistors etc, but no relay's. Thanks fella's!

Question by R3born   |  last reply


DC power + or -? Answered

I have looked at lots of Instructables and websites, but there is a 50/50 split that power flows positive to negative and negative to positive. Which is it? I use both, depending on the circuit I am building it is easier to build one way over the other (NPN and PNP Transistors usually) But I have heard that it used to be thought that positive flowed to negative but I have since heard that the new idea is that it flows negative to positive. I know that everything is supposed to flow from higher concentration (+) to lower (-) but we could have batteries labeled wrong so I don't know. Very confused.

Question by Electric Spectre1   |  last reply


I have a problem testing the DC Motor Controller,please help if you can! Answered

Hi! I want to build a robotic arm for a project,but I got stuck while testing the motor driver on the breadboard. I have followed the instructions from this instructable: https://www.instructables.com/id/Easy-DC-Motor-Controller/ and I connected the pnp transistors the right way(the author confirmed in the commentaries a long time ago) and also like in the diagram. The problem is that when i turn the power on to the circuit,the motor starts to spin(slowly but it has a snail gearing reducer) and the first mosfet is getting very hot very quickly and also if I try to control the circuit by touching the first contact with a positive voltage it doesn't do a thing.I even tried doing only half of it. I tried to reassemble it again many times,changed the transistors with other new ones,checked the connections and after numerous voltage measurements I concluded that the problem is that when I am powering up the circuit for some reason between the pnp collector and ground there is a 12v voltage and the voltage continues all the way to the resistor to the far left,although at the resistor the voltage is dropped to about 7v. I also simulated the circuit in proteus before i bought the parts(i need 6 good working drivers) and it worked fine. It may be a stupid mistake,but please help me if you have any idea what the problem might be!

Question by VladM43   |  last reply


Ideas for circuit bending/hacking/case modding the Intellivision Plug N' Play system? Answered

After much frustration with the lack of response from the controls and finding only one decent game on the whole console I've decided to take apart my Intellivision Plug N' Play (abbr. PNP) system. I was thinking about circuit bending or complete circuit hacking the system but I've come up with a load of parts and fun gadget-y components, but no ideas. Could someone please give me an idea of what kind of fun I should have at the console's expense? A short list of things I know that may help you are as follows: 1. I have many Radioshack electronic components (resistors, capacitors, reed switches, IC chips etc.) Feel free to suggest these things, if I don't have the component you mention I may just grab it. 2. So far I've found ABSOLUTELY NO data on the PNP system so as far as reprogramming the thing, it's somewhat out of the question. 3. Here's some photos (below) of the circuitry; hopefully something will help. 4. It doesn't really matter what you think up (even if it's just something that warps the colors onscreen or makes odd noises, I will try it) Many thanks in advance! If a collab. of ideas work together then I may post the finished product in an instructable! (Yes, credit will be given. If I missed giving it to you feel free to yell at me.)

Question by MacDynamo   |  last reply


Transistor help.... very basic, LDR/LED

I'm trying to make a very simple circuit to light an LED based on light from an LDR. I have all the components, it's a white LED, I'm using two AA batteries, and the LED glows brightly when I attach it to the batteries, but when I attach it to the LDR, it is either dim or dimmer due to the resistance... I'm sure I need to use a resistor for this... I have some assorted PNPs and NPN2222As... I've looked at a couple tutorials, but none of them seem to work... does anyone know how to do this without any (or as few as possible) other components? Thanks

Topic by perkinsb1024   |  last reply


Can anyone make this and post an instructable? Answered

See the schematic and these are the parts and please make a breadboard version IC1: LM555 Timer IC Q1: 2N3906 PNP transistor R1: 100K potentiometer R2: 3.9 Kohm resistor R3: 10 Kohm resistor R4: 47 Kohm resistor C1, C3: 0.01-µF disc (non-polarized) capacitor C2: 1.0-µF electrolytic or tantalum (polarized) capacitor Speaker: 8-ohm, 0.5-watt speaker(i also tried a buzzer) Photoresistor: I used a LDR aren't they the same? The buzzer goes off(not off. it's like explosions"The bomb went off") when light hits the photoresistor.

Question by Hafiz Mohammad Shayan Tariq   |  last reply


copper wire following robot: building a dual Hbridge to drive a robot. but my transistor TIP 42 and TIP 120 overheat Answered

I have a dual hbridge but its overheating im a beginner in electronics and i dont know how to fix this   i have attach a schematics of my circuit...i used 4 npn transistor (TIP120) 2 to control the Hbridge and 2 others that form the hbridge , 2 pnp transistors (TIP42G) ,  (4) 1Megaohms resistors. TIP transistors are able to take up to 150 degrees...i heard of heat sink  and voltage follower to help with the overheat . but i cant make it work. is my circuit correct..if yes how can i get rid of the heat? 

Question by souandji   |  last reply


Replacing the 2N3904 with an SCR

So i made a laser alarm system some time back, it worked good but had one fault, more like a limitation. it made the buzzer ''buzz'' only when the laser was interrupted and the buzzer turned off when the laser was allowed to hit the photo sensor again. i wanted it to stay on until turned off by a switch. someone suggested something called a monostable flip flop but i had no idea what it even meant, then i saw something called silicon controlled rectifier or a thyristor, but i also learned that they have to be made using a pnp and npn transistor, what i cant understand is what transistors should i use to replace the npn transistor on my circuit, the tansistor on my cicuit is 2n3904, input voltage is 5v

Question by walee    |  last reply


P-Channel MOSFET woes - anyone know how to drive one of these things with Arduino?

Hi all, I’m a hobbyist trying to build a digital controller / power monitor for a green power generator project built from an auto alternator. Hoping to use an arduino microprocessor & some simple transistor circuits to power an alternator’s field coil which at 13v can draw up to 10amps of power. From what I’ve read I think I need high side PWM switching because the alternator shares a common ground with its other electrical connections preventing me from using my usual novice NPN based bag-of-tricks. From my reading I assume some sort of PNP or P-Channel MOSFET is in order (components I sadly have no prior experience with). Alternativly I've read about using fancy high side controller ICs to drive regular NPNs but don't want to go that route. So far everything seems to work except I clearly can’t figure this P-channel MOSFET out (IRF6540)!  No matter what I try I always get a high voltage at the drain pin (full-on condition) regardless of what I do to the gate pin. I uploaded a portion of my schematic as a test circuit I think should work from my limited understanding and online tutorials: http://www.curtismasonjohnson.com/sandbox/ProblemCircuit.JPG   - The NPN driver in the drawing (2N3904) by itself works when tested with a voltmeter and toggling the input   - If I replace the p-channel mosfet with a PNP transistor it work as expected. Shouldn’t this mosfet work pretty much the same? My puny TIP127 PNP can't handle the current if I were to hook up the load.   - I’ve tried several IRF6540 components   - I’ve tried connecting the MOSFET’s ground pin via a current limiting resistor directly to ground. Also via the resistor to 13v. No voltage change on the drain pin in either case. Clearly I’m missing something embarrassing and fundamental. I mentioned I’m a hobbiest, right - my day job is managing global marketing programs for fortune 500s and don't know anyone that knows anything about electronics! After years of electronics & robotics projects I’ve yet to be stumped to the point of needing help til now - amazing how much you can self-teach via google and such. This one has me beat – hope someone can help as I have no idea what to do next! Truely appreciated...

Question by cmjstealth   |  last reply


Solar charging a battery with Arduino?

I am making a solar rover robot using an arduino duemilanove. I have a 12 volt solar panel and a 9.6 volt nicad battery. I am wondering if this circuit I sketched http://www.flickr.com/photos/56541142@N02/5229716662/ would allow me to prevent the battery from over charging. The battery is monitored by dividing the voltage and connecting it to analogue input on the arduino. When the battery is fully charged, the arduino sets an output pin HIGH and breaks the connection between the panel and the battery using a PNP transistor. Does the transistor subtract current from the circuit? In the open state will there be more than 9.6 volts entering the battery? here are some links to the robot so far! (without solar installed) Pics! http:// http://www.flickr.com/photos/56541142@N02/with/5229716662/ Video! http://www.youtube.com/watch?v=YZkXnul2j5M

Question by Revolt Lab 


high power LED matrix; is it possible and how?

I've been getting into arduino lately and recently discovered the LED matrix.  I also saw some high power LEDs controlled by arduino using transistors to handle the power.  I wondered if the same idea could be applied to a matrix.  It seemed relatively simple, but when I built the circuit in a simulator (everycircuit- an excellent app), I quickly realized some issues with it.  The attached picture is the circuit in the simulator.  You should get an idea of the flaws of the circuit.  I know it would be pretty simple to use relays instead of transistors, but does anyone have any ideas on how to do it with transistors?  NPN or PNP or both.  I can't figure it out how to do it, but I figured that the collective mind of the brilliant members of instructables could probably manage to come up with something.

Topic by dudes   |  last reply


NPN BJT strange behavior? Answered

My linear power supply design has been using a PNP MJE2955 pass transistor wired to a 2N4401 as a complementary darlington configuration, but this was not an inherently stable design, and would oscillate when adding output smoothing capacitors, particularly MLCC types (with very low ESR). So I decided to try the far more common darlington arrangement, although I am not fond of the higher voltage drop. However the output was oscillating at approximately 3KHz with 1uF output capacitance, with NO input to darlington. I removed the 2N4401 so all I had left was just a 2N3055 transistor with the emitter connected to the output and the collector connected to a 20V supply. The output was ringing like crazy. The oscillation frequency could be changed by adding/removing output capacitance. Why is this happening? How should I go about stopping this oscillation? I originally had a 4.7k resistive load on the output but it did not significantly affect the output oscillation.

Question by -max-   |  last reply


How can I build a 555 timer equivalent circuit out of transistors? Answered

I want to go old school and do things the hard way by building an equivalent circuit of the classic 555 timer. There are equivalent circuits on just about any 555 timer data sheet. Such as here... http://www.national.com/ds/LM/LM555.pdf  That schematic is for a LM555.  First, what would be a good, easy to find, NPN and PNP transistors to use uniformly in the circuit? Preferably something I could get a pack of at Radio Shack just to make this project easier. Also I can't figure out what Q5, and Q6, and Q22 are? Please help. They look like transistors, but each of those ones have an extra lead coming out of it? Is that extra lead just a doubled up (collector) ? Also Q22 has no base, or is the base that horizontal line, but in the opposite direction? I am thoroughly confused already, any help would be great! Thanks in advance.

Question by bart245   |  last reply


How do i make a capacitor charger circuit? Answered

I am talking about one for in a coilgun. i had a old (very old, 1.3mp) samsung digimax 101 digital camera, I decided that since i have moved on it was time to take it apart for the rich insides. I knew what to look for, so i found it; the transformer for the capacitor charging circuit and the big cap for it. I unsoldered the transformer piece, cut the wires from the cap (it was not mounted on the board), and unsoldered the flash which had not 2 but 3 wires coming from it. one was yellow, one was green, and one was black and was attached to the deflector behind the flash. the black wire was connected to a small black piece that looked a lot like the charger transformer but only had two active pins instead of four. im not sure what it is for, i think it is a self resetting fuse, incase the camera short cicuits, but im not sure. any insight on that would also be helpful. Back onto the subject, i would like to know what i need (other than the yellow transformer piece) to make the charger circuit. I have heard there was a transistor, would it be NPN or PNP? there was also a diode, i am guessing one of the black ones, but is there anything else? i have those three things if that is all i need, but how do i solder it all together? thanks in advance, z247 PS: the yellow transformer has only 4 pins that actually do anything, one is between two on one side and is only for support. either that or i accidentaly broke it.

Question by zack247   |  last reply


The classic IRFP250N vs FDP33N25? Which one is best for high power SMPS? Answered

I have an idea to start selling some powermax singing arc kits. In the kit I plan to include all the parts including a printed PCB to create an audio modulated flyback driver. I figure to start off with, since I have no clue what demand would be, I want to play it safe and only get enough parts for 10 - 25 quantity, which works out to be about $40, or about $4 a piece, not including custom PCBs. However, at >$2, the IRFP250 is not cheap even in 10's of quantities on Digikey. Looking to shave off pennies, I found the FDP33N25 for about half the cost of the classic IRFP250N and best part is that it appears to have simalar specs, and in some ways it looks like the FDP33N25 is even better! Bolded parameters are the (I think) prefered values. I do not know much about selecting the best transistor for the job, but I did compare the specs below: IRFP250N: 85mΩ Rds ON, 30A, 200Vds, 2800pf gate capacitance, TO-247, 0.65 *C/W FDP33N25: 94mΩ Rds ON, 33A, 250Vds, 2135pf gate capacitance, TO-220, 0.80 *C/W One thing I am concerned about power loss and therefore switching speed, so the MOSFET must be driven with a 15KHz to 40KHz square wave with very sharp rise and fall speeds. I was able to reduce power dissipation in my last circuit by simply shortening the wire carrying the signal to the gate, as well as adding a complementary pair of NPN and PNP transistors to the output of the 555 timer. That seemed to lower the drive impedance and switch the mosfet more rapidly, but considering that I still need to use active cooling and a brick sized heatsink, I think I can do better. Any suggestions?

Question by -max-   |  last reply


Aurora 9 bar Kit & Custom PCB for Sell

Aurora 9 bar Kit and PCB are now available for sell. ******* Prices are reduced ******* Aurora 9 bar custom PCB price is $7.50 + $2 shipping for US address. The kit is also available at $25 + $5 shipping for US address. All parts except Molex connectors and power supply are included. Kit Contents (as pictured) 16x 120 Ohm (0603) 21x 1k Ohm (0603) 1x 10k Ohm (0603) 2x 1uF (0603) 1x 10uF (1206) 1x AP7333-33 or AP7313-33 (3.3V linear voltage regulator) 3x MMBT2907A or equivalent PNP transistor 12x MMBT2222A or equivalent NPN transistor 1x PIC24F08KA101 (SSOP) 10x 5mm Tricolor LED (common-cathode) 1x 5-way Tactile Switch Notes The PIC microcontroller is not pre-programmed. You need your own programmer to program the PIC microcontroller. The kit is also available with water clear LEDs instead of diffused type shown. Please specify if you want water clear LEDs (Special: $1 less for the water clear LEDs). The kit comes with one extra LED. Power connection cable (see the picture) - optional is available at $2 extra. (International shipping is $17) To place an order, please go to my blog page - http://www.theledart.com/blog/archives/233. You will find purchase buttons. Please view my Instructable for the detailed information on Aurora 9 bar. Contact me if you have any questions. <br>

Topic by ledartist   |  last reply


Smart amplifier design building blocks help? (making an amp w/ auto-volume adjust by controlling gain with running avg)

I am currently working on a simple headphone audio amp that automatically adjusts volume to my preference, regardless of what video I click on when it is plugged into a computer. I am tired of some video's being so quiet that I have to crank up the volume to overdrive to hear it, while other video's blast out sound and burst my eardrums. And of course when watching photonicinduction videos, he often can be hard to hear his voice at really low volume at like 12 at night when everyone is asleep, but then the sparks and hammers come into the picture, it is often too late to crank the volume back down, and thus makes your ears bleed or waking everyone up in the neighborhood! X-(. (Luckily he has included sound warnings, but I am lazy, and will engineer things that do the hard work of adjusting volume for me! :)   ) In a way, I understand that this will minimize the dynamic range, which I suppose hardcore "audiophiles" will go NUTS over me actually WANTING to do that, but none the less, That is what I want. My design currently is just a simple emitter follower with a NPN and PNP transistor is the class AB operation, and to minimize crossover distortion and give a definite gain, I have negative feedback op amp from the output of the totem pole transistor arrangement back to the inputs that feed the base of the low and high side transistor. (obviously, the transistors by themselves are low impedance output, (CV mode) and high impedance input, and have a gain of like 1.) Sorry, no schematics, but you capable of googling it if you want to see what I am describing. As it is, it works fine. HOWEVER, it does not do the automatic volume, or gain control. That is set in stone by a resistor divider network between the feedback and ground (the basic non inverting amp feedback config.) I do not want a fixed gain. I want a electrically adjustable gain. The thing I plan to use to do the automatic adjustment would be a peak detector on the input, which is probably going to be a simple diode and capacitor with a buffer, and a discharge resistor (or constant current drain) across the capacitor to gradually lower the max output, or possibly an integrating op amp that effectively takes a running average. The output of that needs to control GAIN of the primary amplifier, and I want to be able to control the PID of that thing, maybe by tuning the a LCR circuit, or what have you. It is all nice and analog, just the way I like it! :) If ONLY there was some magical (and common) component that I could control the resistance anywhere in the feedback loop, of with a given voltage w/ respect to ground... I was thinking of like a MOSFET, but I would have to deal with the non linearity of the input vs output impedance, which probably changes with respect to everything from the current flowing through the channel, the voltage relative to ground at the source, the temperature, the alignment of the planet's, what mood god is in, etc etc etc. That is too many factors for an open loop control on to model in discrete stuff! And digital potentiometers are out of the question since, well they are digital, I want an elegant simple solution, and the are $$ and difficult to deal with. They have so many requirements that need to be addressed.  I prefer a elegant discrete transistor circuit, but op amps and other basic building blocks are acceptable, (this thing I want to be built over a weekend with with jellybean parts from by junk bin.) if you happen to know of a specific audio chip that does this for me, please mention it, but I will probably not use it, but maybe analyze the internal circuitry and learn how it works.

Question by -max-   |  last reply