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halentech

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  1. Hello, I had make this - Improved short-circuit detector - http://electronicdesign.com/boards/improved-short-circuit-detector (based on http://www.diy-electronic-projects.com/p213-Beeper-to-find-short-circuits) and build it on testing breadboard. I used LM4871, because was cheaper then LM4861. It should be pin compatible as datasheet from Ti says it. My question-problem is, that I cannot make it working. I made it exactly as in schematics, but it is not working. Can please anyone help me to make it working? I have some suspect on shutdown wiring in the schematics, because daatasheet says, that should be connected to - to enable amplifier. for schematics which I use, please see attachment. Thank you very much, Jan
  2. But LF356 has 44V power supply, so it is usable for this project. As I say, I used those opamps in this psu before and withouth problem at all.
  3. What's conclusion is about this modification: Received the following email from Ivan on 02/2010: Ok. I bulid your project about a day ago. Mounted all the parts on the pcb and then concluded that there is some serious problems in this schematics. First, 2N3055 will overheat, so you have to connect two of them in parallel with emitter resistors 0.1ohm/5w. Second, maximal voltage between '+' and '-' of TL081 is 36VDC.If you connect them as it is shown in this circuit diagram that voltage will be about 45VDC, so they will burn down immediately. To fix this problem you have to reconnect all pins number 7 of U1, U2 and U3, emitter of Q3 and 'upper' end of R19 to out of an 7809 with 18V zener diode between 'common' pin and '-' of 3300uF cap, and input of 7809 connect to '+' of the same cap. Now, on pin number 7 and mentioned parts you'll have 27VDC, and total voltage will be 32.6VDC. Third, instead of using 3300uF, use 4700 or 6800uF/63VDC to reduce the ripple on higher currents (2-3A). The rest of the circuit is perfect. I like it cause it is so inexpensive and easy to make with those simple reconstructions i mentioned.
  4. Why do not use cheap LF356? I have one channel power supply made with those OPAMPs and works great. I think, that those are good alternative for MC34071 and TLE2141
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