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  1. hi guys, the voice activated switch has certain drawback like when your voice is not of the same pitch when you have recorded it. in case you have a hoarse voice or use a high pitch or shouting, it won't be able to recognize your command. just like one of the features of a cellphone on voice activated dialing.
  2. hi hearmewell, nice user name you've got. all the problems encountered in building this project has been addressed in this forum. the datasheet you were asking is also here. browse thru all the Q & A here. good luck
  3. hi thanhyuse, i don't know how far you are into electronics, but base on your question i could probably presume you are a real beginner. if that is the case my friendly advice is to look for circuits not using mosfets as the output stage and using single rail supply. but if you insist in building that circuit, pay attention to the following; R13 & 16 10ohms should be match (same value when tested) R14 & 15 220ohms should also be match Q1 & 2 should also be match you should a single ground point entry Q6, 7, 8 & 9 should be properly heatsinked i have build that circuit and it was good, just follow the recommended parts. use high quality electrolytic caps. hope this would help you :)
  4. ;)hi, since you need a long interval the accuracy of using the 555 is questionable since i believe the 555 was not designed for this although it can still be used. try using a programable timer ic like the CD4536 or the CD4541 w/oscillator. you can program this as long as 36hrs. :)
  5. :)hi, most infrared LEDs have a high current rating of 100ma. however the supply voltage is not posted, even if the Vcc is 12v it would supply 0.12ma. better do a google search for "infrared LEDs" to find the appropiate led. ;)
  6. :)hi there, it seems a few members have a problem having this project work. my xperience when i first built this project cost me 2 damage CD4027. the most common problem is the damage CMOS. another member was asking if the series/parallel signal diode (IN4148) is presented correctl in the schem. yes, it should be connected as presented in the schem. remember that what the author had in mind when he designed this circuit that it can be used to test transistors in-circuit, so he has to employ such circuit configuration. am not trying to be the spokesman of the author but let me try to explain why this circuit is used in the design: looking at the schem you will see that the 2 sets of series IN4148 are connected in series with the D.U.T. via its Collector terminal. it works this way, they allow only a current path thru the DUT as long as the transistor is fully saturated. thus insufficient current would flow thru parallel resistances resulting that 1 or both LED would be dark or unlit. i hope this would make things clear. in fact i have made revisions to this circuit using only 1 ic (CD4093) a quad 2-input NAND Schmitt Trigger in place of the 555 & 4027, but still using the same basic set up on the testing side, and it work just fine. i could check diodes, SCRs & transistors and it could also show the transistor type. also pls remember that the output at pin 14 & 15 are at opposite of its other state. when 14 is high 15 is low which causes both LED to flash alternately. so if only 1 LED lights up continously, no alternate flashing, it means one of the output is not functioning. so what would be your logical conclusion. :) :)
  7. hi amigo, it seems that all your request for datasheets have not been asnwered. where are those parts used. those parts could probably been discontinued thats why you could not find the datasheet. :)
  8. :)hi, to simplifiy, why dont you use an SCR to turn on the relay. once the SCR is turned on it will remain on until such time you cut off the power. all you have to do is place a timing circuit to the gate of the SCR. :)
  9. :)hi, try to check your foil layout, there might be some short or there is a mistake in making the layout. also you might have damage the CMOS flip flop or its defective. remember that is static sensitive device. ;)
  10. :)musta kasamiko, try http://doc.semicon.toshiba.co.jp were is that used, i might be able to help you out kabayan :-*
  11. :)hi bonanz, sorry i was not able to complete my reply, one way to solve your -5v swupply source is to use a 10v transfo. this is how you do it, 1. series 2 resistors 2. shunt the resistors across the rectified output 3. from the junction of the 2 resistors, this is where you tap your ground 4. connect the usual filters 5. connect your 7805 for +5v and 7905 for -5v suggested resistance value is 47K 2w hope you can benifit from this :)
  12. :)hi, i hve finished the transistor tester after a long delay and ''I HIGHLY RECOMMEND THIS PROJECT FOR ALL ELECTRONIC HOBBYIST" ;) ;) ;) ;) 8) 8) 8) thanx to this site.
  13. :)hi bonanz, you said you would be measuring only positive voltages, now what would happen if you accidentally reverse your probe. wont your voltmeter get burned? i believe one of the reson why this device was designed to have a dual supply is bcoz of that. if you reverse the probe your display will have a negative sign. since you said you only have a 5v positive supply, try using LM7905 to get a 5v negative supply. hope this solves your problem.
  14. :)hi EDY am i correct to assume that you are trying to build an electronic ignition system, well here's a few that you can consider; 1. MJ10008 npn 175w 450v 20A (darlington) TO-204 2. MJ10023 npn 250w 400v 40A (same) TO-3 3. MJ10015 npn 250w 400v 50A (same) TO-3 :) these are motorola products. hope this can help
  15. :)hi everybody, i will not try to comment why the author configured U5 that way, but here is a very simple suggestion, try substituting with LM386 for U5, see what happens. if the circuit board had been set use an ic socket, solder wires to it and connect to the appropiate holes on the board. LM386 pin configuration: 1. gain 2. inverting input 3. noninverting input 4. ground 5. output 6. Vcc 7. bypass (if you will use connect a ceramic cap 0.01uf to grnd if not leave it open 8. gain this is the output amp of my electronic stet. ;)
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