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  1. EdwardM

    Need help for 4009b hex inv buffer

    Hi Saadmir the 4009 allows you to do level shifting, for example driving TTL logic from a CMOS source.  The supply voltage, Vdd has a range of +3 to +20v and Vcc, whilst the datasheet doesn't say, should have the same range. In a level shifting application, Vdd would be set for the input...
  2. EdwardM

    TTL pulse for counter

    Hi MikeB Take a 4.7Kohm resistor from +5v and connect it to the input.  Connect a switch between input and ground. This circuit will count every time there is a transition from high to low voltage on the input pin.  The first thing you may notice is that each time you hit the switch and expect...
  3. EdwardM

    stroboscope

    Hi reference the relay switching rates, I once designed a system to play a sound organ and it used relays to fire each note, as I remember the switching time was in the order of 10-20ms, you just need search almost any electronic suppliers parts pages to get the details Ed
  4. EdwardM

    ADC0832 Interfacing

    Thanks MP that's exactly what I was suggesting but in reading over what I've posted, it does need more detail.  However I did take econs' question literally and pointed to one possible way to solve the problem. Ed
  5. EdwardM

    ADC0832 Interfacing

    Hi econ there is an excellent introduction to opamps, particularly chapter 4, which will help to solve your problem Best of Luck Ed http://homepage.mac.com/tbitson/weather/TI_OpAmp_Tutorial.pdf
  6. EdwardM

    256 outputs from 8 bit

    Hi Scott start small and build up to it... the previous post will get you initially 4 bits, building up from there (16 possibilities and beyond) There are things like the 8255 chip which will expand an 8 bit interface.  Lots of PICs allow multiple I/O ports which can then be used to drive the...
  7. EdwardM

    Voltage controlled mains lamp dimmer

    ...or nearly as much fun Ed ;D
  8. EdwardM

    Timed Status Indication w/ Multicolor LEDs

    Hi jonny your requirement should be fairly easy to satisfy... It can be done in a number of ways, for example, a microprocessor (PIC or other) can with suitable circuitry, detect the presence of master power and illuminate a green LED, likewise it can detect the presence of current in the...
  9. EdwardM

    Voltage controlled mains lamp dimmer

    Hi Alun I almost feel a competition coming on, how few components are absolutely necessary for a VCD? Ed ;D
  10. EdwardM

    About Visual Basic6 and RS232 ASCII communication

    Hi cyw1984 first thoughts: I presume you don't want to send all 3000 at once to the 8051 but just a current value? You could do something like... Public Sub Send5Chars(Value as string) 'The 5 characters have been previously made into a string which looks like "nnnn" MSComm1.Output =...
  11. EdwardM

    What happen to sonsivri.com

    Who knows? you could try http://www.electro-tech-online.com/viewtopic.php?t=8556 and others Ed
  12. EdwardM

    relays - SPST, SPDT, DPST, DPDT?

    Hi Paul SPST - Single Pole Single Throw - Otherwise known as an on-off switch. SPDT -Single Pole Double Throw - Single pole changeover switch, ie, with no power to relay, centre connects to one side. When power applied, centre connects to other side. DPST - Just two independent switches like...
  13. EdwardM

    Frequency detection

    Hi Jarmund personally I'd use a PIC processor, first use an op-amp with plenty of gain to amplify the sine wave so that it clips at the supply voltage - you now have a square wave at the input frequency.  Feed this square wave into a PIC, ensuring that the input square wave is within the...
  14. EdwardM

    Duplicate threads and circuit requests.

    Very good thinking  ;D Ed
  15. EdwardM

    Need help repairing and setting up this old computer.

    Hi Dazza the light stays on on the floppy drive... usually indicates that the ribbon cable is rear about face Ed
  16. EdwardM

    Rookie Student: A Question of Tools

    Hi Alun agree absolutely about the soldering iron. To Seth...buy the best temperature controlled iron you can afford, preferably one that can use different sized tips for soldering anything from battery terminals to 0402 resistors Ed
  17. EdwardM

    Light Computer

    Hi Alun hopefully there should be no need to use optos as it's all 12v supply Ed
  18. EdwardM

    Light Computer

    Hi Steve the only thing I would add to Shariars response is a slightly modified power supply Ed
  19. EdwardM

    Light Computer

    Hi Steve first problem, for me at least, is that I can't read the diagram as the quality is too low, can you post a higher quality image? Ed
  20. EdwardM

    12vdc->9vdc

    Hi Scott boredom is a good thing, it's amazing what you can learn I lean towards always finding the simplest way of making something work, apart from my earlier post, the next way forward would be to look at the next simplest way. With your specialized transmitters, if you or someone could...
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