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  1. duke37

    PCB & environmental problems

    Dissimilar metals in contact will have an electrochemical potential between them. If there is an electrolyte, there will be a current and corrosion will occur. The problem is much more severe when external voltages are present which will promote rapid corrosion. This can be seen in battery...
  2. duke37

    Resistor Chart

    Look up Wikipedia, preferred number. The E12 series is probably all you want. If you get a set you will not need to go to the store often. Don't worry about looking like a fool, you should see me!
  3. duke37

    Wanted help with electronic generator govenor

    I do not have time to go through all the details but, 1. Vo=Vcc*fin*C1*R1*K . K is given in the data and is approximately 1. 400Hz 6V then C1*R1 = .0015 If C1= 100nF then R1= 15k or C1=10nF, R1=150k 2. Fmax=I2/(C*Vcc) From equation 2, chose a value of C1 to get the frequency...
  4. duke37

    Amp

    I would not think that the 12V socket is a source. There is an integrated circuit with about 5 legs shown in the photo. this is likely to be the audio amplifier. If you get the details of this, you can check whether there is the correct voltage on each pin (do not short pins together) and you...
  5. duke37

    Vertical hold problem

    Perhaps it was comfy at the first house and has gone into a huff. If it is an old TV, you could try a fresh frame output valve. Squashing of the picture bottom is due to a lack of sufficient current in the frame output stage. This can be due to the capacitor feeding the supply to the...
  6. duke37

    led and potentiometer questions

    You cannot run three leds of 2.2V from a 6V battery, two will be enough, a suitable series resistance will be needed in each string. You will have 72 strings each taking 20mA so the total current will be 1.44A. You do not say what the potentiometer is supposed to do. If it is to control the...
  7. duke37

    Alarm Cable

    Just measure the diameter with a micrometer and look up the table. If you hav'nt got a micrometer, strip a length of the wire and wind 10 turns round a nail and measure the winding length. If the cable gets warm, this indicates a considerable voltage drop. Will your circuit tolerate this?
  8. duke37

    Is converting voltage to freq like creating a tone?

    A tone is a frequency which uses a transducer to vibrate the air. A microphone turns these vibrations into electrical signals at very low levels. A V-F converter will produce electrical pulses at a frequency proportional to voltage input. Your recorder should be able to record these...
  9. duke37

    New valve amp build

    1. The load on a valve is determined by the optimum impedance to get the maximum power out. It has nothing to do with the output impedance of the valve or the transformer resistance. Check up 'load line'. 2. The transformer is to transform the speaker impedance to the optimum load for the...
  10. duke37

    Wanted help with electronic generator govenor

    The servo data that I saw says that the servo takes in a series of pulses of different width to determine the servo action. This seems to be a complicated method which is used so that another seven servos can be used on the same channel. The servo may just take the average voltage as its...
  11. duke37

    Hardware Debouncing Help

    Another thought The chip will contain more than one gate. The unused gates should have their inputs defined to stop oscillation.
  12. duke37

    DC step up

    There are several ways of doing this, it depends to some extent on the power required. At present I am making a 12V to 300V supply based on a 4047 cmos chip driving two fets which feed into a transformer wound on a TV line output transformer core. I am hoping to get 20W out of this to supply...
  13. duke37

    Hardware Debouncing Help

    Without capacitors at the input and output of the stabiliser, it can go into oscillation and produce random voltages. Any long connections have significant inductance so earth can not be defined as earth and there may be no 'dead zone'. As I said, I have not used one of these breadboards...
  14. duke37

    Hardware Debouncing Help

    Yes, there should be capacitors before and after the stabiliser but I do not see them so I said he did not have them. He said he was using the 74LS14 Schmitt trigger device. Duke
  15. duke37

    Hardware Debouncing Help

    I've never used one of the plastic breadboards, my last breadboard was made of pine with some one inch nails knoched in for connections. You do not have capacitors before and after the voltage stabiliser. Also, the earth wire seems to go round the long way. This should be as short and direct...
  16. duke37

    Simple FM Transmitter carrier wave

    There is a tuned circuit formed from the inductance and two capacitors in series. The transistor gets an input via its emitter at low impedance and outputs the same current at high impedance. There is therefore a power gain which is used to maintain oscillation. VHF oscillators are often...
  17. duke37

    Please help guyz..!! New to electrical circuits

    A TV controller uses infra red light to control the TV. If you use the same system to put a beam across the tunnel entrance, then, when the beam is broken action can be taken. You can have the sender one side of the tunnel and the receiver the other or have a reflector with the sender and...
  18. duke37

    Wanted help with electronic generator govenor

    This looks like a difficult project. One thought, if you start a timer from the ignition with a pulse length of 20ms, then if the next ignition pulse comes late, the later it is, the more the throttle needs to open. Using set/reset ICs would give a PWM directly. I am sure someone could give a...
  19. duke37

    Please help guyz..!! New to electrical circuits

    A infra red beam can be broken by the car indicating that it has entered the tunnel. However if it is intended to stop a crash from a car coming the other way, you will need to activate this before the car enters the tunnel and show a red light if the tunnel is occupied. What will turn off...
  20. duke37

    power requirements for xmas lights

    As you say, LEDs need DC, they also need a current controlled supply, not voltage controlled. An easy way of controlling current in an AC circuit is to place a capacitor in series. If this is followed by a rectifier, then that is all the necessary circuit. If you go to a DC supply you...
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