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  1. duke37

    How Do I get the wire to heat up?

    Platinum is used because it is resistant to oxidation and acts as a catayst. It promotes reaction between gas and air and is of course used in car catalytic convertors. Thin fuse wire is used in glass fuses but you will need to extract it which may be difficult. Some battery gas lighters use...
  2. duke37

    Help connecting a pin

    You are right, the resistor in circoit B should be only there to take photodiode current due to ambient light and perhaps could be omitted. The phototransitor could easily supply the 0.18mA to the Schmitt trigger. Glad you have it working OK.
  3. duke37

    Single supply 5V LM324 Half-Wave Rectifier

    Show us a circuit The LM324 can provide an output to within 1.5V of the supply i.e.3.5V, The diode will need 0.7V to turn on. Have you run out of voltage?
  4. duke37

    ADC & DAC

    Not quite! If you use 8 bits you have 256 steps to fit your analogue signal to. When you convert back you will get the steps. There is also the problem of accuracy of the convertors and interference between the digital and analogue signals. An interesting experiment is to charge a capacitor...
  5. duke37

    Help connecting a pin

    I cnnot understand your diagrams with the power supply being inverted. Why not keep 5V at the top. The TTL series inputs sit with the input high and need to be pulled low. I attach some diagrams:- A. Your original circuit B. Using the phototransistor to pull the input low. The resistor would...
  6. duke37

    Help connecting a pin

    Yes, you are right. According to the data sheets, the 74LS14 needs 0.18mA at the lower threshold. The 10k cannot supply this with 0.8V across it.even if the phototransistor is fully off. You could add a transistor amplifier but the easiest way is to use a CMOS chip (4093?) which will not load...
  7. duke37

    Controlling My Office Water Heater

    I took your idea and separated the control and latch functions, otherwise they are similar. I should have said the the 12V needs to be applied for only a moment rather than should be applied. I sketched the diagram and scanned it. How did you add the red lettering?
  8. duke37

    two way switch wiring help

    In the UK, the bare wire in the cable is used for the earth (ground). It must be sleeved inside any box with yellow/green sleeving. An earth must be taken to any light fitting in case they have a metal case so that a fluorescent fitting or crystal chandelier is earthed. All earth wires go back...
  9. duke37

    Controlling My Office Water Heater

    A simple circuit is attached. The 12V relay should be energised for only a moment. The contacts on both relays will need to take the full load current.
  10. duke37

    NiCd Zapper

    This is very much like a flash circuit in a camera. I managed to beg a used disposable camera from a shop that did the developing. The shop assisstant told me to be careful since it could bite - she was right!
  11. duke37

    need help!

    Hi Steve, On your comments. 1. I have used 4093 gates to drive mosfets in low frequency inverters. The fets don't get warm so the switching speed is fast enough. The repetition rate here is quite low. The simple 4093 oscillator circuit gives equal on/off times, not so easy with the 555 but...
  12. duke37

    need help!

    I will try to upload a diagram of a simple circuit which will give rectangular pulses with equal on/off times where the voltage and frequency can be controlled I suggest using a primitive battery charger as the power source to give the required voltage and mains isolation. The TIP3055 will...
  13. duke37

    12v to 220v inverter design

    You do not say how the optocoupler will be used, it seems that you are complicating things. If the frequency is constant then a CMOS 4047 oscillator can be used to drive the mosfet(s) and will run on 10V. A transistor with a collector resistor going to 10V will also do the job if you insist on...
  14. duke37

    need help!

    Hi, The requirement as I understand it is for a pulsating DC voltage with a frequency range of 60 p/s to 200 p/s with a variable voltage between 1 and 20V capable of a current up to 2.5A. If this is so, I would suggest a variable voltage DC supply and a 555 timer and fet to switch this to the...
  15. duke37

    Output impedance of microphones

    Hi, Magnetic microphones produce a very low voltage which can be masked by noise picked up in the cable or generated in the amplifier. The best way of alleviating these effects is to use a transformer to give higher voltage without noise addition. This results in a higher source impedance...
  16. duke37

    Woo-Woo Need help with running car on water electronic bored?????

    Hi, In your first post you stated you wanted 62V at 10 to 17A, This is a very high power for a battery to provide, assume 62V at 15A = 930W which would need 77.5A out of a 12V battery. Perhaps there is a decimal point in the wrong place. Later you say 1.24V at 10 to 20A, Assume ~15A this is...
  17. duke37

    Need help identifying wire

    Constantan is used to make resistors also.
  18. duke37

    op-amp

    I would dispute your statement, but it depends on what you mean by high impedance. The op-amp must be connected as a voltage follower not an inverter to get a high input impedance. The venerable 741 can manage well over 1M whilst the jfet op-amps (TL071 etc) can do much better. A mosfet op-amp...
  19. duke37

    Woo-Woo Need help with running car on water electronic bored?????

    It is entropy man! But seriously, many 12V inverter circiuts can be found on the net. Electrolysis using AC will not produce hydrogen, it will produce a mixture of hydrogen and oxygen in an ideal ratio (H2O) to react back to water. Could blow your head off!
  20. duke37

    Circuit Wanted To Buy...

    A ceramic record player stereo pick-up would do two axes, it would have a relatively high voltage suitable for matching to a fet. A weight would need to be added instead of the needle.
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