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Everything posted by Hero999

  1. Seriously, save yourself the trouble and buy a ballast. The electronic ballast inside the screw fitting CFL will be tailored to deliver the correct current to that lamp. The lamp needs a ballast to limit the current to the correct level, in order for it to work properly.
  2. RL symbolises a load, whether it be a lamp, relay, buzzer etc. The second circuit is wrong - they forgot the decoupling capacitor; something which is explained on the datasheet.
  3. Active components such as semiconductors actually process or control electrical energy. Passive devices such as resistors, capacitors and inductors dissipate or store energy.
  4. A capacitor always passes AC and blocks DC. However a filter can be made with a capacitor and resistor to allow DC and block DC.
  5. http://en.wikipedia.org/wiki/Relative_permittivity
  6. No, an arc can form when the relay is not switching, if there isn't enough clearance between the contacts. The breakdown voltage in air is typically 1kV/1mm, so for 2kV the gap between the contacts needs to be at least 2mm. A high voltage relay may be filled with a gas or vacuum which has superior dielectric properties to air so a smaller gap can be used. Can't you just invert the logic signals for controlling the relays?
  7. The current rating is not a problem. It's better to go higher than lower. Using a power relay to switch low current signals is only a problem at very low voltages. The problem with using a lower voltage relay is the contacts can arc over and what's worse it it could be unpredictable.The relay may seem fine most of the time but it could suddenly arc over due to ambient ionising radiation.
  8. Is 2kV the peak voltage? What's your budget? This will not be cheap. There are reed relays which can do this: http://www.gigavac.com/pdf/ds/hv/gr6cba335.pdf Rs and Farnel both sell reed relays which will do this: http://uk.rs-online.com/web/c/relays/reed-relays/reed-relays/?applied-dimensions=4294526583,4294528392,4294526582,4294528391&esid=cl_4294967294,cl_4294959386,cl_4294959493,cl_4294538434,cl_4294957569,cl_4294956147,cl_4294538400,cl_4294538399&m=1&sort-by=P_breakPrice1&sort-order=asc&pn=1 http://uk.rs-online.com/web/p/reed-relays/5111307/ http://uk.rs-online.com/web/p/reed-relays/5111313/ http://uk.farnell.com/jsp/search/browse.jsp?N=203394+110240136+110184433+110209613+110203522&Ns=P_PRICE_FARNELL_UK|0&locale=en_UK&appliedparametrics=true&getResults=true&suppressRedirect=true&isRedirect=&originalQueryURL=/jsp/search/browse.jsp%3FN%3D203394%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_UK%26divisionLocale%3Den_UK%26catalogId%3D%26skipManufacturer%3Dfalse%26skipParametricAttributeId%3D%26prevNValues%3D203394 http://uk.farnell.com/cynergy3/dat71210/relay-reed-pcb-12v/dp/1882600 http://uk.farnell.com/cynergy3/dat70515f/relay-15kv-5v-coil/dp/1877557
  9. Hero999


    How about starting with the part number which is written on the component?
  10. Hero999


    Ever thought of searching for the part number using Google?
  11. You've been asked questions because you haven't provided enough information. No one will be able to do what you want regardless of how much money you pay them, unless you provide them with a detailed specification of what you want and are able to answer the appropriate questions.
  12. Why not? Have you tested it? What is it you want to measure the speed of?
  13. Why not use radar? http://www.ebay.com/itm/Bushnell-Velocity-Speed-Gun-Sports-Radar-Gun-101911-/390773879599?pt=LH_DefaultDomain_0&hash=item5afbf0332f
  14. You're being a bit vague. There are other ways to implement a monostable than a 555 timer such as a couple of logic gates, transistors, a comparator or a flip-flop.
  15. An old topic but I was curious myself so I thought I'd find out. That works but the circuit is very difficult to read. Fortunately it's easy to increase the contrast to make it readable.
  16. What's the point of this thread? I was tempted to delete it.
  17. http://en.wikipedia.org/wiki/Resistance_thermometer#Four-wire_configuration
  18. http://www.mini-box.com/M4-ATX?sc=8&category=981 http://www.powerstream.com/DC-PC-12V.htm
  19. You're right. It has a built-in input and output buffer. If you design the circuit in accordance with the datasheet, you won't have any problems. What are you doing with the data once it's been sampled by the ADC? Why not bais the ADC input at half the supply voltage or use a precision full wave rectifier and calculate the RMS value using a microcontroller?
  20. 1) If the mains neutral wasn't connected to earth, it could float at any voltage. Suppose someone connected a 10kV autrotransformer to the mains and the seondary became shorted to earth? The mains would then float at 10kV above earth, causing fire as the insulation isn't rated to that voltage. 2) Became metal doesn't burn like most insulators do. 3) It depends on what you're doing.
  21. I don't know much about programmable logic. All I know is PLDs tend to operate from a lower voltage than 12V so you need a regulator such as the LM78L05 for the logic. You'll also need level shifting and buffering on the output to boost the logic levels to 12V. The logic inputs can be connected to the 12V inputs using potential dividers to lower the voltage. An IC such as the CD40109 or CD4504 can be used to translate the 5V output to 12V. http://www.ti.com/lit/ds/symlink/cd4504b-ep.pdf http://www.ti.com/lit/ds/schs099b/schs099b.pdf
  22. http://www.ee.ucr.edu/~stan/courses/eecs168/eecs168_12wint/lab6/lab6.html
  23. Is that with the engine running? That's quite low and would indicate a flat battery. Try it, a lower voltage shouldn't do any harm. It might just become unreliable.
  24. It should be possible to wire the DVD player directly to the car without and other circuitry.
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