كود تفعيل العضوية - الابلاغ عن روابط لاتعمل - صيانة التلفزيون - الحاسبة - الأعضاء المتميزين - البرامج و المخططات - بث مباشر للقنوات الفضائية - إذاعة - تردد القنوات - بحث
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منتدى الإلكترونيات قسم الالكترونكس لمناقشة الافكار والمعلومات المتعلقة بالهندسة الالكترونية للمبتدئين والهواة والفنيين - Electronics |
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#1 |
مهندس
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![]() ELECTRONIC STETHOSCOPE (HEART BEAT MONITOR) USINC PIEZO SENSOR (TWO WIRE TYPE)AND MICRO CONTROLER
A heatbeat is a very low frequency, about 16Hz. A piezo sensor picks up 3kHz frequencies well, but works poorly at low frequencies. An electret mic works well at all audio frequencies. The optional circuit blinks or flutters the LEDs for each heartbeat. I think only one colour will light most of the time. The circuit won't drive a 3-pins LED, use a two-colours LED that has only 2-pins or two separate LEDs connected back-to-back. The circuit with the 741 opamps is WRONG! My circuit corrected the errors on its schematic and on its parts list. If it drives a speaker then it will probably make acoustical feedback howling because the microphone will hear the sound from the speaker and it will go around and around. It is supposed to drive earphones. Everything connected to ground on the schematic are connected together. The max voltage in the circuit is only 9V so 16V or higher voltage electrolytic capacitors should be used. R11 is a 2k to 10k audio-taper (logarithmic) volume control. The arrow is its slider. C3 and C4 are 47nF which is 0.047uF. What is a "modual"? Here is my parts list: You should use what is on the parts list. C3 and C4's values determine the cutoff frequency of the lowpass filter. * * * *lized plastic film capacitors are used because they are made with a 5% tolerance. C5 must be a 0.1uF ceramic disc because ceramic disc capacitors are good at very high frequencies and C5 stops the LM386 power amplifier IC from oscillating at a very high freqiency. A * * * *lized plastic film capacitor is an inductor at very high frequencies. On the other site you said the noise was hum. Hum is radiation from the mains and is usually picked up by unshielded input cable from the microphone. My schematic shows the cable shield from the microphone. The unshielded parts of the wires should be very short. The long wires on a breadboard can also pickup mains hum. A small pcb or stripboard should be used. If you are using an AC adapter instead of 9V batteries then its poor filtering would cause hum. The casing and shaft on the volume control could pickup mains hum. Try connecting it to the circuit's 0V. You can use a plug and a jack for the microphone if the wires from the jack to the circuit board are short and the cable from the microphone is shielded. Describe "a relly loud noise when i adjust r11 the volume controll". Is it a crackling static noise when the pot is turned? Measure to see if it has a DC voltage. It should be less than 20mVDC. Is it acoustical feedback howling because the microphone hears the speaker and the sound goes around and around? Do not use a speaker, use headphones. The wire from the pot to the LM386 IC can pick up interference if it is long. It should not be longer than 2cm. Your TL072 dual opamp has a high amount of input offset voltage. It can be blocked from the volume control by adding a non-polar 3.3uf capacitor (or two back-to-back 10uF capacitors) as in my sketch here. There is no capacitor in the circuit that takes 30 seconds to charge. Most take only 5 seconds max. Download Attachment: It is good that the capacitors fixed your project. I have never seen a pH meter but I saw some circuits. Search for pH meter circuit in Google. There are lots of circuits. Please don't post the same question on two websites. Digikey has thousands of LM4040 2.5V reference ICs in different packages and from different manufacturers. My corrected version of this project has an output for headphones which is line level. Plug it into the line level input of your pc or attenuate the output with 2 resistors down to mic level and plug it into the "guess what" input of your pc. |
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#2 |
مؤسس موقع القرية الالكترونية
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![]() شكرا لك أخي على هذه المساهمة الجميلة وبارك الله فيك..
المشروع عبارة عن دائرة مكبر صوت حساسة جدا تستخدم كسماعة للطبيب وتمتاز بأنها تعطي مؤشر سمعي وضوئي لنبضات القلب .. |
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اعلانات اضافية ( قم بتسجيل الدخول لاخفائها ) | |||
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#3 |
مهندس
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![]() ممكن استخدام بري امبليفير هد مسجل قديم وشكررراااا د:محمد عيد
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