Post by thread:[pic]: Can you amplify with a single 2n2222 ??

I am trying to drive a piezo speaker using a pic and I want to amplify my output, or just make it louder. I am making a little tone generator for a tabletop oven that will sound when the thing stops. It has a built in timer, but no bell to let you know the thing has stopped. So, using what amounts to the Freqout command from a stamp, I generate my tone, but it isn't loud enough. Can you make a little amplifier using a single 2n2222 transistor? Any help appreciated. -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> >Can you make a little amplifier using a single 2n2222 transistor? Certainly. Look up class-A amplifiers. Alternatively, you can use the transistor as an open collector driver, which is a class-C amplifier. -- Dave's Engineering Page: http://www.dvanhorn.org Got a need to read Bar codes? http://www.barcodechip.com Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with two or five digit supplemental codes, in an 8 pin chip, with NO external parts. -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

rad0 wrote... >I am trying to drive a piezo speaker using a pic >and I want to amplify my output, or just make it >louder. > >I am making a little tone generator for a tabletop >oven that will sound when the thing stops. It has >a built in timer, but no bell to let you know the >thing has stopped. > >So, using what amounts to the Freqout command from >a stamp, I generate my tone, but it isn't loud enough. > >Can you make a little amplifier using a single 2n2222 transistor? Sure, no problem at all. Take your 2N2222 transistor and connect its emitter lead to ground. Connect the base lead to one end of a 10K resistor, and connect the other end of this resistor to the PIC output pin. Connect one end of your piezo to ground, and the other end of the piezo to the collector lead of the 2N2222. From the 2N2222 collector connect a 1K resistor to your +5V supply voltage. If the loudness problem was that the PIC was having trouble driving the piezo's low impedance, this will solve the problem. If it doesn't help, try connecting the top end of that 1K resistor to a higher DC voltage to get more output. Keep in mind that most of these piezo elements are **VERY** frequency sensitive: drive them with too low or too high a frequency and you can barely hear them; drive them exactly at their resonant frequency and they can be ear-splitting. You may want to experiment with the frequency, to make sure this isn't in fact the source of your problem; I never have any trouble getting good volume from one of these things, even when driven right from a PIC pin, so long as I use the right frequency. Hope this helps a bit... Dave -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

Certainly! That's what transistors do! You will need a higher voltage source to drive the collector. (12V) A simple common emitter amplifier will drive a Piezo. You might also look into driving the Piezo directly with two pic output pins and push-pull it for twice the drive. rad0 wrote: {Quote hidden}>I am trying to drive a piezo speaker using a pic >and I want to amplify my output, or just make it >louder. > >I am making a little tone generator for a tabletop >oven that will sound when the thing stops. It has >a built in timer, but no bell to let you know the >thing has stopped. > >So, using what amounts to the Freqout command from >a stamp, I generate my tone, but it isn't loud enough. > >Can you make a little amplifier using a single 2n2222 transistor? > >Any help appreciated. > >-- >http://www.piclist.com hint: To leave the PICList >EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu > > > -- * | __O Thomas C. Sefranek tcsspam_OUTcmcorp.com |_-\<,_ Amateur Radio Operator: WA1RHP (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz ARRL Instructor, Technical Specialist, VE Contact. hamradio.cmcorp.com/inventory/Inventory.html http://www.harvardrepeater.org -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

You wrote... >let me give this a try - thanks You're welcome. One thing you might try is to hook up your piezo to the output of an audio signal generator and sweep the frequency around until you find the loudest output; then replicate this same frequency with your PIC. Worked for me... Dave -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu

At 01:34 PM 2/10/02 -0800, you wrote: >So, using what amounts to the Freqout command from >a stamp, I generate my tone, but it isn't loud enough. > >Can you make a little amplifier using a single 2n2222 transistor? Well, sure, but I bet that's not the problem. The PIC has a fair bit of output drive for a piezo (which basically looks like a ~10n capacitor (depending on size). Try this: Try driving *two* port pins 180' out of phase, and connect the piezo across them. This gives you double the P-P voltage across the piezo. Higher supply voltage will help with both the output drive and the loudness. Make sure the PIC supply is well bypassed. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" RemoveMEspeffTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com 9/11 United we Stand -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

At 01:59 PM 2/10/02 -0800, rad0 wrote: >let me give this a try - thanks If you have a pair of output pins, you can do a bridge drive, but be careful. You want to take both pins to the same state, before taking them to opposite states. 00,01,11,10,00... rather than 10,01,10... The reason is that with the second sequence, you make a capacitive voltage doubler, and are sinking large current pulses into the protection diodes, risking CMOS latchup. -- Dave's Engineering Page: http://www.dvanhorn.org Got a need to read Bar codes? http://www.barcodechip.com Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with two or five digit supplemental codes, in an 8 pin chip, with NO external parts. -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

lots of good suggestions, thanks everyone. I changed the prgram around to step thru some frequencies and found a more correct freq. And this will be ear splitting enough for my purposes. I thought the little piezo tranducer would act like a speaker, but I see now that is not really true. I have been trying different combinations of frequencies and different durations and different rates of repeating the tone. If you repeat it fast enough, it sort of rings. - the dog seems to really hate that ;-) the amp isn't really necessary, but it worked fine with a higher voltage I'm going to try the 180 out of phase technique and the push pull next. - but it's already loud enough -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

At 03:20 PM 2/10/02 -0800, rad0 wrote: >lots of good suggestions, thanks everyone. > >I changed the prgram around to step thru some frequencies and >found a more correct freq. And this will be ear splitting enough >for my purposes. Most of these are resonant at 2700 Hz, which for some reason is the point where human hearing works the best. >I thought the little piezo tranducer would act like a speaker, but I >see now that is not really true. It's response curve would put most rollercoasters to shame. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu

{Quote hidden}> -----Original Message----- > From: David VanHorn [SMTP:EraseMEdvanhornCEDAR.NET] > Sent: Sunday, February 10, 2002 8:49 PM > To: RemoveMEPICLISTEraseMEEraseMEMITVMA.MIT.EDU > Subject: Re: [pic]: Can you amplify with a single 2n2222 ?? > > At 01:59 PM 2/10/02 -0800, rad0 wrote: > >let me give this a try - thanks > > > If you have a pair of output pins, you can do a bridge drive, but be > careful. > You want to take both pins to the same state, before taking them to > opposite states. > > 00,01,11,10,00... rather than 10,01,10... > > The reason is that with the second sequence, you make a capacitive voltage > doubler, and are sinking large current pulses into the protection diodes, > risking CMOS latchup. > You could do the push-pull using the proposed 2N2222 transistor. Configure the transistor on common emitter mode as sugested with a 1k collector load. Then connect PIC pic to the transistor base via a 10k resistor and also to one side of the piezo. The other side of the piezo goes to the transistor collector. Mike -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

"Alternatively, you can use the transistor as an open collector driver, which is a class-C amplifier." I don't get it. Maybe I'm from the old school where Class C amps were only used for RF (I can't recall a single audio application for a stage biased Class C and conduction angle for each cycle was significantly less than 180 degrees) where the tank circuit provides for the balance of the re-creation of the waveform (tank, or LC resonant circuits being analogous to balance wheels or tuning forks of sorts). The "open coll." app above sounds more like the 2n2222 is being used as a switch, perhaps in PWM mode as in class D or the like. Jim {Original Message removed}

At 08:41 AM 2/11/02 -0600, Jim wrote: > "Alternatively, you can use the transistor as an > open collector driver, which is a class-C amplifier." > >I don't get it. > >Maybe I'm from the old school where Class C amps >were only used for RF Where does RF start, exactly? Connect an antenna to it. >(I can't recall a single audio >application for a stage biased Class C and conduction >angle for each cycle was significantly less than >180 degrees) where the tank circuit provides for the >balance of the re-creation of the waveform (tank, or >LC resonant circuits being analogous to balance wheels >or tuning forks of sorts). Probably because they were worried about fidelity. If you're driving a beeper, fidelity is right out the window. You can drive a beeper as part of a resonant circuit, with the beeper acting as a lossy tank capacitor. >The "open coll." app above sounds more like the 2n2222 is >being used as a switch, perhaps in PWM mode as in >class D or the like. You could do that too. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

I would, in the future, tend to shy away from the classification of an 'amplifier' stage as Class A, B or C unless that stage were truly working as an amplifier with specific bias set up so as to actually attain a particular bias and hence operate as a Class A, B or C stage - this is as opposed to a single device operated as a simple on/off switch in some sort of pulse width modulation mode. As to where RF begins - that's easy. Does it involve 'radio frequencies' and the technologies classically employed to modulate, amplify, detect, filter, demodulate or radiate EM energy as opposed to 'audio frequencies' which have in past decades normally 'modulated' an RF carrier in order to transmit intelligence though the ether from point A to point B? I'm afraid today's 'digi-head' has blurred all distinction between the two ... Jim {Original Message removed}

----- Original Message ----- From: "Jim" <RemoveMEjvpollspam_OUTKILLspamDALLAS.NET> To: <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU> Sent: Monday, February 11, 2002 12:43 PM Subject: Re: [pic]: Can you amplify with a single 2n2222 ?? ... > As to where RF begins - that's easy. Does it involve > 'radio frequencies' and the technologies classically > employed to modulate, amplify, detect, filter, > demodulate or radiate EM energy as opposed to 'audio > frequencies' which have in past decades normally > 'modulated' an RF carrier in order to transmit > intelligence though the ether from point A to point > B? Audio is ELF. An audio-frequency circuit still radiates electromagnetic waves, just not very efficiently. > > I'm afraid today's 'digi-head' has blurred all > distinction between the two ... The boundary _is_ very fuzzy, but most animals can't hear beyond about 200kHz... /\/\/\/*=Martin -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

"Audio is ELF. An audio-frequency circuit still radiates electromagnetic waves, just not very efficiently." Very incorrect in all but perhaps a very few ill-designed products. Most of us responsible for actual RF design don't call possible 'spuriuous emissions of AF energy' over 100 dB down from a 'box' "radiation of electromagnetic waves". Leakage flux perhaps (as from a power xfmr) - but not 'radiation'. I realize I'm addressing a majority digi-head crowd - some of this discussion is only underscoring that point. No offense meant to any digi-head on the list. We couldn't possibly do what we do in the field of RF today without uC's or the talented programmers and designers who actually make those devices 'sing' and 'dance' ... Jim {Original Message removed}

----- Original Message ----- From: "Jim" <EraseMEjvpollspamspamBeGoneDALLAS.NET> To: <RemoveMEPICLISTKILLspamMITVMA.MIT.EDU> Sent: Monday, February 11, 2002 1:12 PM Subject: Re: [pic]: Can you amplify with a single 2n2222 ?? > "Audio is ELF. An audio-frequency circuit still radiates > electromagnetic waves, just not very efficiently." > > Very incorrect in all but perhaps a very few ill-designed > products. Most of us responsible for actual RF design > don't call possible 'spuriuous emissions of AF energy' over > 100 dB down from a 'box' "radiation of electromagnetic > waves". Leakage flux perhaps (as from a power xfmr) - but > not 'radiation'. Sorry. I meant the electrical part of the amplifier, not the sound waves. Should have said "an audio-frequency circuit will emit extreme low frequency electromagnetic radiation as a side effect of its functioning." /\/\/\/*=Martin -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> >No offense meant to any digi-head on the list. We couldn't >possibly do what we do in the field of RF today without uC's >or the talented programmers and designers who actually make >those devices 'sing' and 'dance' ... Why does it matter to you, wether the output is to an antenna, or a resistor? If I drive a parallel combination of L and C, with an "open collector" transistor, using pulses that are shorter than half the oscillation period, that looks like "class C" to me. The fact that the signal is propagated to air by the capacitor, rather than to the aether by the inductor, makes no difference to the transistor. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

"Audio is ELF. An audio-frequency circuit still radiates electromagnetic waves, just not very efficiently." "Very incorrect in all but perhaps a very few ill-designed products. Most of us responsible for actual RF design don't call possible 'spuriuous emissions of AF energy' over 100 dB down from a 'box' "radiation of electromagnetic waves". Leakage flux perhaps (as from a power xfmr) - but not 'radiation'. I realize I'm addressing a majority digi-head crowd - some of this discussion is only underscoring that point. No offense meant to any digi-head on the list. We couldn't possibly do what we do in the field of RF today without uC's or the talented programmers and designers who actually make those devices 'sing' and 'dance' ... Jim" Jim, others: I'm afraid your not quite correct here Jim; as stated by others, there is no magic frequency where AF ends and RF begins - it is most definitely blurred. What is important is Efficiency, as efficiency for each purpose varies with frequency. But there definitely are audio frequency "RF" transmitters, and these are not "ill-designed products." For example, the U.S. Navy uses what most would consider as "Audio Frequencies" in their equipment designed to communicate with submerged submarines. Though efficiency is horrendous, the importance of the task makes the inefficiencies acceptable. Also, you should not assume that the audience cannot rationally consider the topic, as many have mixed disciplines. While I probably could not match your level of expertise, I have been workinging with RF as an amateur (HAM) since the '70s. I'm sure there are many readers that have even more experience than I. Bruce. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 09:59 AM 2/13/02 -0500, you wrote: >But there definitely are audio frequency "RF" transmitters, and these are >not "ill-designed products." For example, the U.S. Navy uses what most would >consider as "Audio Frequencies" in their equipment designed to communicate >with submerged submarines. Though efficiency is horrendous, the importance >of the task makes the inefficiencies acceptable. The ELF transmitters in northern Russia, Michigan and Wisconsin are almost *beneath* the audio range (< 100Hz!). Here's one take on it:- http://www.provcomm.net/pages/joe/introlf.htm "The "long wave" spectrums of frequencies are divided into three main grouping by convention. These are; LF (Low Frequencies) 535 to 150 kHz VLF (Very Low Frequencies) 150 kHz to 3 kHz ELF (Extremely Low Frequencies) 3 kHz to 300 cycles (approx.)" Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" speffSTOPspamspam_OUTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com 9/11 United we Stand -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Spehro Pefhany wrote: > At 09:59 AM 2/13/02 -0500, you wrote: > >> But there definitely are audio frequency "RF" transmitters, and these >> are >> not "ill-designed products." For example, the U.S. Navy uses what >> most would >> consider as "Audio Frequencies" in their equipment designed to >> communicate >> with submerged submarines. Though efficiency is horrendous, the >> importance >> of the task makes the inefficiencies acceptable. > > > The ELF transmitters in northern Russia, Michigan and Wisconsin are > almost *beneath* the audio range (< 100Hz!). NONSENSE! They are <100KHz! {Quote hidden}> > > Here's one take on it:- > > http://www.provcomm.net/pages/joe/introlf.htm > > "The "long wave" spectrums of frequencies are divided into three main > grouping by convention. These are; > LF (Low Frequencies) 535 to 150 kHz > VLF (Very Low Frequencies) 150 kHz to 3 kHz > ELF (Extremely Low Frequencies) 3 kHz to 300 cycles (approx.)" > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the > reward" > spamBeGonespeffSTOPspamEraseMEinterlog.com Info for manufacturers: > http://www.trexon.com > Embedded software/hardware/analog Info for designers: > http://www.speff.com > 9/11 United we Stand > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > > -- * | __O Thomas C. Sefranek KILLspamtcsspamBeGonecmcorp.com |_-\<,_ Amateur Radio Operator: WA1RHP (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz ARRL Instructor, Technical Specialist, VE Contact. hamradio.cmcorp.com/inventory/Inventory.html http://www.harvardrepeater.org -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> -----Original Message----- > From: Thomas C. Sefranek [SMTP:EraseMEtcsEraseMECMCORP.COM] > Sent: Wednesday, February 13, 2002 3:46 PM > To: @spam@PICLIST@spam@spam_OUTMITVMA.MIT.EDU > Subject: Re: [pic]: Can you amplify with a single 2n2222 ?? > > NONSENSE! They are <100KHz! > > Technically you are correct, they are <100KHz, but also <100Hz! Have a look at http://web.tiscali.it/vlfradio/zevs/zevs.htm http://hypertextbook.com/facts/2001/LisaWu.shtml Regards MIke Rigby-Jones -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 10:46 AM 2/13/02 -0500, you wrote: >>The ELF transmitters in northern Russia, Michigan and Wisconsin are >>almost *beneath* the audio range (< 100Hz!). > >NONSENSE! They are <100KHz! Hard to argue with that, as 82Hz (the Russian frequency) and 76 Hz (the American frequency) are both < 100Hz AND (way) < 100kHz. ;-) Here's a page, direct from the US navy on the Wisconsin transmitter: http://enterprise.spawar.navy.mil/spawarpublicsite/docs/fs_clam_lake_elf.pdf There is another "band" below ELF, called ULF that starts around 30Hz, but I don't know if it has any practical use. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" spamBeGonespeffKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com 9/11 United we Stand -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.