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  2. liuliying

    how to design a battery jack for unknow phones

    In addition to the positive and negative electrodes, there are two legs of the battery, which are battery parameter detection and battery temperature detection. Now most mobile phone batteries have removed the battery temperature detection pins. The 3 feet are now the most batteries in the market. www.pcbindex.com
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  5. No. An old condenser mic uses 48V and needs a preamp with a very high input impedance. It does nothing in your circuit. A modern electret mic (look it up in Google) is a condenser mic with 48V stored permanently in its electret material and has a Jfet inside that has a very high input impedance. The datasheets of electret mics show that the Jfet current is about 0.5mA and needs 2V to 10V, so your circuit will not work since the current in the 47K resistor reduces the voltage and current much too low. For 2.5V across a 0.5mA electret mic and a 5V supply then the resistor must be only (5V - 2.5V)/0.5mA= 5k but the 5k resistor and any other load (your volume control) loads down the output level. I use a 10k resistor and an 8V supply. Then it feeds a preamp with a 100K input impedance.
  6. Homemade MIC Amplifier Loudspeaker connection circuit You can connect condenser MIC with any amplifier circuit as given below diagram . This circuit will work very well with any type of Audio amplifier. Use only 5-6v for condenser MIC for best result. Audio amplifier circuit need 6-24v as per amplifier specification. Connect the positive terminal of mic with 47 k resistor in series with positive supply and negative terminal of mic is directly connected to negative supply or ground. And enjoy this easy homemade MIC Loudspeaker. This Circuit works with any type of amplifier circuit. If you have no any audio amplifier then you can make an small amplifier very easily with LM386 ic. This is very popular amplifier ic and available on any electronic part store. For more Click here You can check for more simple circuit here circuitspedia.com
  7. this is base on BPI-R2, with 4 4G module desin. We can work with our customers to provide overall solutions 4G Multi-network fusion terminal 4G Multiple 1.jpg750x361 31.4 KB 4G Multi-network fusion server 4G Multiple 2.jpg750x225 21 KB overall solutions 4G Multiple 1 system.jpg1248x477 96.3 KB PCBA inside: 4G Multi-network fusion 1.jpg750x503 63.4 KB more aout BPI 4.0 Service : http://wiki.banana-pi.org/Successful_case
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  9. I have a question, there are so many development boards in this world, banana pi, raspberry pi and so on, could you pls tell me more about these boards? What's your opinion?
  10. The datasheet of a CD4017B shows that its output current into a 2V LED when it has a 5V supply is only 3.5mA or less (looks dim). Your circuit is mixing an old TTL 555 with an output voltage fairly low with a Cmos 4017 that needs a fairly high clock input voltage. A bad mix. I used a 74HC4017 (high current Cmos) clocked with a Cmos 555 and it makes very bright LEDs and since they are both Cmos they work together reliably.
  11. Lasseryie

    How to Design a PCB Layout

    PCB Layout Tutorial: For High-Quality PCB Design http://www.apogeeweb.net/article/89.html Asymmetric source/drain MOS transistor LPNP MMC
  12. audioguru

    0-30V Stabilized Power Supply

    Why do you show an LT1038? it is obsolete and is not made anymore. It is impossible for it to dissipate 32V x 10A= 320W. Its datasheet shows that with a huge heatsink with fan or with liquid nitrogen for cooling it can dissipate only 120W. Its control circuit gives 10A only when its input to output is a few volts and cuts the max current to 2.5A when the input to output is 30V.
  13. Why do you show text that talks about an NPN transistor but you show a schematic with a PNP transistor? The Circuitspedia PNP circuit is missing the important diode parallel with the relay coil. The diode is shown on their NPN circuit.
  14. detonatorinf

    0-30 Vdc Stabilized Power Supply

    Hahahaha. I promise i will make a better one.
  15. audioguru

    0-30 Vdc Stabilized Power Supply

    Surface mount ICs on adapters? Solder that was dripped on from up high and heated with a blow torch? All I can say after seeing your project is "EEK!".
  16. Aman bharti

    0-30V Stabilized Power Supply

    10A High Current Adjustable Voltage Regulator using LT1038 http://www.circuitspedia.com/10a-high-current-adjustable-voltage-regulator-circuit-diagram-using-lt1038/
  17. http://www.circuitspedia.com/transistor-as-switch-working-how-transistor-works/ For more detail click here A small Positive current required at the Base terminal for the turning on the transistor. By sending varying levels of current to the base, the amount of current flowing through the collector to emitter may be regulated. When we apply a small Positive supply at base , then Current between emitter and collector will passed and we say that transistor is turn on. A very small amount of current may be used to control a large amount of current, this property is known as amplifier . . A Diode with Parallel of relay coil in reverse connection is necessary for protection the transsistor. This must connected on both PNP and NPN
  18. Aman bharti

    DIY - AUTOMATIC GARAGE LIGHT

    Automatic Room Light And Security Alarm circuit Using PIR Motion Sensor
  19. detonatorinf

    0-30 Vdc Stabilized Power Supply

    Sorry, audioguru. My post sounded like i was describing how the circuit should work but i was just explaining the behavior of the opamps. None of the 3 opamps were working as intended. The problem was caused by my lack of atention while copying the schematic to Kicad. The opamp footprint for U2 was printed with the negative and positive inputs inverted. Two jumpers solved the problem and now i have a working power supply. I attached some images. Really ugly, ain't it? But it was my first time learning how to make one. R7 resistance is 0R22. I couldn't find the 0R25 resistor recommended for a 5A power supply. Also, three 2sc5200 in parallel are used as output transistors.
  20. I'm a research analyst for a small management consultancy firm. Our primary focus is on helping innovative startups make their ideas and inventions become realities. We're currently doing a research project for a startup company that is working to revolutionize the PCB design software space by adding usability and automation features that currently do not exist. They are passionate about enhancing accessibility to design software by offering most of their software features at little to no cost. To help assess how this software addresses the needs of PCB designers, we put together a brief questionnaire. This survey is intended for PCB designers across all user types and skill levels. It should only take a few minutes of your time to answer our questions and survey completion will give you the option to receive a free premium trial of the PCB design software. Survey Link: https://s.surveyplanet.com/By7uffhxm
  21. audioguru

    0-30 Vdc Stabilized Power Supply

    No and No. U1 has a gain of 2 times and a 5.6V Zener diode. Therefore its output is 11.2V, not 33V. A 5.6V Zener diode does not change its voltage when its temperature changes but an 11.2V Zener diode increases its voltage if it gets warmer. The BD139 and the output transistors are emitter-followers. Their emitter voltage follows their base voltage but at high current, their base voltage is 1V to 1.5V higher than their emitter voltage. Then when the output voltage is 30V the output of U2 must be 32V to 32.5V.
  22. detonatorinf

    0-30 Vdc Stabilized Power Supply

    Sorry. You're right. I confused the order of the ICs. U1 (reference voltage) outputs 33v and U2 (voltage control) outputs 0,640V to the base of the BD139.
  23. audioguru

    0-30 Vdc Stabilized Power Supply

    My Rev 6 July, 2014 schematic shows that opamp U1 makes the 11.2V reference, U2 is for the voltage control and drives the output driver transistor with 0V to about +32V and U3 is for the current control and has an output from -1.0V to about +27V. If the output has a low voltage (or is shorted) and a high current then the NPN output transistor in U2 will get hot. A tiny little surface mount package cannot dissipate much heat.
  24. detonatorinf

    0-30 Vdc Stabilized Power Supply

    U3 only outputs 0,640 volts. When the voltage control pot is rotated to the left or right, the variation in the readings are minimal. The voltage only raises to 10v when U3 gets too hot. U1 outputs 33v and also gets hot. RV2 has no effect on the readings.
  25. audioguru

    0-30 Vdc Stabilized Power Supply

    I did not calculate it but I think a tiny surface mounted opamp for position U2 will get too hot if the hFE of the driver and/or output transistors is low.
  26. detonatorinf

    0-30 Vdc Stabilized Power Supply

    Wow! After long 4 months of waiting, my package with five TLE2141CP finally arrived from China. And for my "surprise" none of them worked. Both U1 and U3 got extremely hot and began to smell. Turns out two resistor got burned!! Just minutes ago i found a store in my country that sells the original MC34071. God... so much time wasted. I'm ordering them tomorrow ASAP. Just a advice for Brazillians interested in building this project. The online store Proesi is selling the SMD version of the MC34071.
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