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  1. duke37

    Blown Regulator!! SOS!

    The data sheet for the TS7815 that I saw said 23V max input. I could not find OF1 CZ.
  2. duke37

    Sharp Microwave Fan not working

    If the fan is stiff, it might only be necessary to clean and lubricate the bearings. The voltages in a microwave are exeedingly high and can be retained on a capacitor even when turned off. Great care needs to be taken.
  3. duke37

    Help with time delay relay circuit

    Kris, That looks good. The only thing that I have reservations about is the high current of the fuel solenoid. Does it have a very high current coil to energise and then a low current coil to hold? Duke
  4. duke37

    AC to DC converter (using envelope detector)

    Your example is an AM signal. Do you just want to measure the amplitude of a constant sine wave? It all depends on the accuracy you want. A full wave precision rectifier followed by a low pass filter would be about as good as you can do.
  5. duke37

    Active low or active high signalling?

    I would not think it matters. You may however consider a fault condition and whether a high or a low fault would be best.
  6. duke37

    I come to you cap in hand :(

    I do not have details of delay relays. What I have seen in an old RS catalogue is that they are expensive. Auto relays are much cheaper and could be delayed with a simple circuit. You could do some investigation of the car wiring and relay details.
  7. duke37

    I come to you cap in hand :(

    A time delay relay providing an alternative supply to the glow plugs may do. Glow plugs take a lot of current so the relay will need to be fat enough to cope. The wires will also have to be substantial and , of course, you will need a beefy battery. You could energise the existing relay but...
  8. duke37

    Help with time delay relay circuit

    The CMOS circuit which I showed earlier works in a similar way to the one you show. A diode is used instead of a transistor but otherwise almost identicle. The CMOS circuit will have a couple of spare gates which could be used to trigger a warning when sloshing commences. You will need to...
  9. duke37

    Help with time delay relay circuit

    In this circuit, the input will normally be low, Q1 will be turned on and the capacitor will be charged. Th 555 output will be low and the 2N3055 will be off. If the input goes high for a short time, then the output will not change until the capacitor is discharged. Intermittent input will...
  10. duke37

    Questions about colpitts oscillator design?

    After 50 years, the memory gets a bit dim! I looked at the circuit and forgot that this circuit is that of a Clapp oscillator with a small series capacitance. If you are running it as a Colpitts, you should take that capacitor out of the tuned circuit and place it between C1 and the base, then...
  11. duke37

    Questions about colpitts oscillator design?

    I canot answer you questions wilh certainty but here goes. A. The resistors R1 and R2 should be connected to the base. The wires show crossing without connecting. B. The loading on the emitter should be small so that the oscillator is not affected. C. C1 and C2 will be much higher than...
  12. duke37

    Help with time delay relay circuit

    Perhaps something like this would work. Note that there are two extra gates in the 4093 which will need their inputs tied to something. I am too tired to check the logic tonight.
  13. duke37

    Bi-Polar LED Circut

    If the solenoids are fairly thirsty and 10 or 20mA for the leds will not make a difference, then the attached should work.
  14. duke37

    Sine Tone Generation Help!

    This thread goes on a bit and I have not followed it all the way. There were top octave generators (e.g. MK50240) which gave the 12 notes of an octave. These were divided down to give all the notes on the keyboard. The output was square wave but for 19 notes, two or three low pass filters...
  15. duke37

    Cant figure out transistor operation in this cct

    The gain of the pair will be R233/R232 +1 = 47
  16. duke37

    How to calculate the value of Zin and Zout???

    Q1 is a voltage controlled oscillator, the frequency is varied by the varying voltage altering the transistor capacitance. The oscillator is very lightly loaded by the 2.2pF capacitance, so looking into the oscillator, it will have a high impedance. This is stepped down by C12, C13, L2 and L3...
  17. duke37

    Valve (tube) amplifier schematic help

    You can provide 12.6V 0.15A or 6.3V 0.3A (AC or DC) as you say. The recommended tolerance if I remember correctly is +/- 7%. If you set the voltage correctly, the current will be right. The anode current will be very low in your circuit and so a low heater voltage may give enough emission...
  18. duke37

    Maximising 12v battery performance

    An old style ignition system takes a large pulse out of the battery and gives a lower output with lower input voltage. What system do you have? Could you get an ignition system which is tolerant to different input voltages?
  19. duke37

    heat switching relay

    Could you just replace R1 with Th2?
  20. duke37

    Use LED to denote current flow in AC circuit

    I talk to myself also - very enlightening. The images work OK for me except the simulation which is too dark.
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