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boombar

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About boombar

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  • Birthday 11/16/1982
  1. As I mentioned earlier, I'm using an old transformer I found. Just missing 400V. And it's not easy to order custom transformer here since they're not very cheap. I will probably benefit more by putting few transistors. That's why I chose this power supply. It didn't use transformer tap for 2 voltages. There is nothing to look at. Its just rectified 325VAC and gives 460VDC. The original circuit had a IGBT with a lots of zeners between base and ground (directly) giving about 430V all together, and resistor between collector and emiter. I would gladly do it that way, but in that case I would have to order from Germany, and I think 100pcs in package. Thank you all.... I believe these 2 schematics will do the job.
  2. Yeah. Decade is right. Screen grid need very low current. I overcalculated a bit and caused confusion. Sorry. Maximum screen grid power dissipation for 6L6GC is 5W. So screens for all four tubes will dissipate maximum of 20W (right?), that means 0.05A on 400V. Right? But I will not be driving tubes so hard since their lifetime is drastically decreased. Sorry guys, I'm still on experimental phase of learning tubes...
  3. Thank You Ante for Your reply. I found an old transformer i want to use for my tube amp. It's perfect, but mussing 400V for screen grid. I't doesn't realy need full 1A of current. Sorry. Just to supply four 6L6GC screen grid voltages, but don't want to blow something in power supply (instead of fuze) in case of overload. As it looks I'll probably have to buy correct
  4. No need for microcontroller. Make detection when heater is on and off (comparator?) 1. When heater is on, signal from comparator powers red half of the LED, and keep green half off via inverter. 2. When heater turns off, red goes off, and green turns on. This signal drop trigers 555 which again keeps red led on for next 10-20 sec. In this case both lights are on, and LED glows orange. 3. After 555 times out, it turns red off, but green stays on until next cycle. And all over again. Only problem is how to triger 555 (monostable). Since trigger pin needs ti go low to start 555 and back high before 555 times out, if not, out pin will stay high forever. Maybe a capacitor could be connected to trigger pin of 555 like this:
  5. http://www.mitedu.freeserve.co.uk/Circuits/Interface/irext.htm
  6. I need to lower voltage from 460V DC (sometimes goes even to 470V) to 400V DC. Need to supply up to 1A max. It's probably possible to achieve that with some zeners and a transistor... is it?
  7. You CAN jam police radar by emitting radio waves in direction of radar (front). Laidar works the same way as radar, but instead of radio waves it uses light. The principle is the same, laidar uses laser beem which bounces of car and returns at differen wavelength. Doppler effect. Now, about IR LEDs. You don't need fast oscilator to drive LEDs. Mentioned wavelength of 920nm does have something to do with frequency, but not in that way. It means that wavelength of light is 920nm (372826086.957 Hz). It is just below visible frequency range. Visit http://www.sengpielaudio.com/calculator-wavelength.htm You should probably use many more LED's since they're weak and because laser signal has all power directed at one spot, so you'll need more LEDs to overpower that signal. If you do attempt to build jammer, make shore to have turn off switch easily accessible to switch it off quick so cops don't get suspicious, and let them measure your speed at their second attempt. But if jamming is not illegal (probably is) in your country, then don't worry. Good luck with research......
  8. As I understood, they want to connect ampermeter to computer port and get data on monitor... If so, make ampermeter with 7107 chip. Download datasheet for it. In there You can find how to make ampermeter. 7106 drives 7-segment 3 1/2 LED display. So take 7-seg to BCD converter (like 74C915). You should be able to connect it to parallel port on Your PC. Then all You got to do is make little program to monitor ports memory register and print number on screen. I'm not sure how parallel port works. There are some controll pins on the port.
  9. Here's URL with tutorial and simple schematics. Look for picture for Astable operation (in the mddle of document). http://www.uoguelph.ca/~antoon/gadgets/555/555.html Some simple schematics and calculator for 555 can be found here: http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm There's even sample for driving LED's To prevent false triggering of 555, connect PIN4 to V+ (directly) and PIN5 to ground via 10nF ceramic capacitor. Hope this helps
  10. It's a small CAPACITOR. I don't believe it's even a calculated one. It stands just to cancel verry small noise. Goes before active component so the noise doesn't get amplified to the level that effects signal quality. Think of it as twisted pair, only on PCB level. To be an inductor, it has to be single track in zig-zag, so it defenetly is NOT an INDUCTOR. Bye.
  11. Anybody know how to make ICL7106 based resistance-meter turn on automaticaly when resistance is connected and go off when resistace is removed. Something like stand-by. It's auto ranging meter with two ranges: 0-19 Ohm and 20-2000 Ohm. Measuring current must be lower than 1mA. Right now works fine with 0.1mA. One of my problems is that I can't make it work without analog common. That's another how-to.... Thanks
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