Jump to content
Electronics-Lab.com Community

f3x

Members
  • Posts

    15
  • Joined

  • Last visited

    Never

f3x's Achievements

Newbie

Newbie (1/14)

0

Reputation

  1. Hi. You probably missunderstoodf what i was saying. 1) I want to do a SPICE simulation of a circuit i have build. 2) This cricuit have a lm386 3) The simulator i have do not have lm386 modeled 4) Searching google for model result in no construtive hint. 5) In fact it only show that alot of ppl can't find it. 6) It is acceptable for me to substitute the lm386 IC for another one beter modelised 7) I am asking if anyone know of such similar IC 8) In the worst case senario i'll modelise the lm386 according to the datasheet 9) Internal circuit in the datasheet miss some information 10) I am also asking if someone knwo what kind of transistor is used in lm386 11) Or if anyone ever modelised a spice circuit out of a datasheet Thanks.
  2. Hi. I am in the process of making an SPICE simulation of the project Electronic Sthetoscope 2. However i cannot found any model of lm386. Googling at it looks like this is something alot of ppl have dificulty to find. I am wondering if any of you know a chip that have similar utility but easier to find model. I no one know such chip or knwo how to obtain a lm386 spice... I'll try to modelise the circuit in the datasheet. If i do that is there anything i need to know ? About transistor ? What are FET - CMOS. What is used in lm386 ? What is the part that look like a diode with a circle around it ? Thank you in advance.
  3. Just seen at digikey that this particular model is in sold in package of 2000+ !! anything else to recomand ?
  4. I undestand an opamp can overload... but how can a potentiometer overload ? does it have to do with headphone impedance ? Can i use a preset voltage divider before the lm386 then a potentiometer to reduce a bit the gain ? What are those ? is this a way to setup transistor ? I've seen audio mixer .. those are opamp used in addition mode rigth ? I really do not want to go in that route... the current setup is already complicated. I'd rather use K.I.S.S. philosophy. All i want is preventing mylself from damaging the expensive chipcorder or the computer soundcard. [edit] Just seen this Fet mixer project http://www.electronics-lab.com/projects/audio/034/index.html so basicly all i need is to add 2N3819 Junction FET and one capacitor / resistance ?
  5. As you said.... I need an attenuator to reinject chipcorder output to the LM386 I need an attenuator to (optionnally) plug the output of the electronic sthetoscope to computer mic input Both need to be somwhere arround the volume control potentiometter. I somehow fear that there will be too much attenuator in that region Do you need something special to prevent the normal flow from leaking in all those attenuator ? Op-amp buffer ? The last thing i want would be using an hardware switch to choose between mode: - chipcorder playback - realtime hearing - realtime hearing + mic output btw can the volume control be after the lm386 ? So you can merge the chipcorder output and the lm386 output and after that, control volume ?
  6. Yes, i had this question. Can you really plug the output of the lm386 to Microphone input Or you need to go rigth before the volume control to do that ? Your noise sound like aluminium paper being folded near the mic. I hope this isnt the pop and crack that is tipical to opamp audioguru last described Good luck in your project
  7. from reading the small footnotes and reading other TI datasheet, i am under the impression that 7V means (Vcc+) at 7V and (Vcc-) at ground or Vcc at +- 3.5 v how long does it take to take a 9V battery to 6V ?
  8. Hmm, i have one question What do you mean by the TL074 behaving badly when the voltage dropdown to 6V ? Because i have to find some research question on the circuit, and the (Noise/distortion/whatever happen) Vs input voltage seem an interesting subject. Or i can just test experimentally the curve Voltage/current vs input frequency wich is a bit less interesting. Or maybee i can analyse what happen arround the LM386 without your "rectifier"
  9. Hi ... I have exatcly two guess to make on that topic 1st (less likely ) is the quality of the microphone 2nd ... you have inversed R6 and C4 or C3 and R5 (or R7) making it a highpass filter that cut at 100hz instead of a lowpass filter that keep 0-100hz Pls make sure your capacitor are at the rigth place. I can also see you are using one led instead of two or a dual ... coud this have any impact ? -------- to audioguru: finally about the input voltage, i have realised that two 9V battery is quite big for the "portable" project we are trying to make. So my guess is that i'll be ok with my current pieces and draining +- 4.5 V from a 9V battery. at the worst cases the 9V will get to 6V wich is +- 3V wich is still acceptable.
  10. Well ... i sort of know what i want. I'm building this to identify certain heart song and enphasis them thus a bandpass Oh well i was proud of the opamp i choose as i figured it was good quality etc. I'll wait before doing another digikey order as last one was quite expensive and it's many trouble. The main reason i should switch is what you call the " input bias voltage " what are the consequences of that being unregulated ? Well i guess you conviced me, the cricuit is mostly what i need Do you have any reference / part number for affordable shielded cable ?
  11. I am wrong to beleive that the only place where -9V is needed is at the opamp ? Then the redisign would be in choosing resistance / capacitor values ? In splitted voltage.. the chip i use can work at +- 8V Max recommanded Is there an easy way to get +- 8V from a 9volt battery ? Those two, i understand now... I guess C5 is like C6 C4 ... is grounded so i understand also but what about c3 ? so the attenuator is basicly a voltage divider to fit the need of the LM386 input. good to know. --------- thank you for your help I have one last question.... Do you have anny comment on the two "filter cricuit" I decided to adopt ?
  12. Now, how exatly i assure that the input bias is correctly configured ? If i have ground and 9V... the input bias is 4.5V ? meaning that i need to keep at least 4.5volt anywhere in the circuit ? If so ... i may switch to your positive / negative power source. Sorry to be a noob but what exatly you mean by couple the audio ? You mean that between C2 and C6 the sound alwais go in the sema direction ? Will this still be true if we change the central filter to target otehr frequency ? What are the advantage of using such polarised capacitor instead of normal ones ? Is it only a matter of electrolytic capacitor being easier to find at high value (1000uF)? It won't work with a 3V battery that drops to only 2.0V over its life! A 9V battery voltage drops to 6.0V. Well the electret work from 1.5V and so does the current opamp i have choosen. one of my problem is that the recorder chip work at a very low voltage and it's the more expensive part of the circuit so i tougth i'd keep everything low. Please explain this. For the headphone at the end is it the voltage or current wich is important ? a switch will be added .... what do you mean by attenuator .. resistance, opamp used as a buffer ? Thank you for your quick reply
  13. Thanks you, well i'll see for my quad opamp ... i may change it latter. Is the noise twice as it's a quad versus a double ? If not do you have any quad you recommand ? What do you mean exactly by inbut bias ? I see that you are using some electrolytic capacitor in your circuit. Aren't they polarised to only one direction, a bit like a diode ? If so ... doesn't the sound need to go in both direction as it have +- v Also considering other chips i have my input source is more likely to be 2*AA (3V) Than 9V .... does it makes any major difference ? I need to put a recorder chip in the stetho... Is there any place you suggest me to *plug* the recorder input and the playback output ?
  14. Hi everyone Tanks for the interesting reading (20 pages is A lot ! ) Like many others I have, chosen this stethoscope as a school project. My particular study in the team is about different heart frequency, and thus i need to have multiple optional filters... e.g. No filter, low pass, band pass. After recording different stethoscope song I have arbitrary found those values: Low pass 640 Hz (song in higher frequency sounded too much like noise) Band pass Fc = 160Hz, Width = 160 Hz. (about 90 to 300 after rounding pieces value) I have found that a professional 3M Littman e4000 have those frequency: Extended range 20-1000 diaphragm 200-500 "precision" 20-100 <- the current circuit fit this category which is good ;) I initially tough I could do this using only opamp but after reading I
×
  • Create New...