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  1. duke37

    Remote Glow Plug Ignitor

    You say the glow plug is just a resistance and that the battery is capable of very high current output. Power in a resistance is proportional to voltage^2 so if you supply 7.4V to the plug, it will need to be connected for 1/(7.4^2/1.25^2) of time, I think. This is about 3% of time. You will...
  2. duke37

    Voltage Regulator

    I would guess that it is a switching regulator which switches rapidly to reduce the dissipation in the output transistor. The output will be 0V or 12V which will be too much for Q1 so the resistor is included to reduce the feedback drive. I imagine that the circuit will produce a pulse width...
  3. duke37

    Help with inverter

    Yes, please answer the questions. I have just made a 12V DC to 300V DC convertor using a pair of fet transistors and a home made transformer on a TV line output transformer core. I used 1 turn/volt and used old wire from TV scan coils. I get 20W out at an efficiency of 80%. Fets may not be...
  4. duke37

    Diode I believe?

    3.2V seems to be high to turn on a SCR. A 3.3V zener diode in series with the gate would increase the necessary voltage. There is normally a resistor gate to cathode, usually below 1k. This could be lowered to reduce sensitivity.
  5. duke37

    help of a 23A battery to 12v Car battery project

    It is usual to show the positive voltages above the negative voltages. A 16V capacitor will have a little bit of leeway when running on 12V. Overvoltaging any component is obviously risky. Make sure that the capacitor is connected the correct way round or it will fail.
  6. duke37

    Thermometer accuracy..sensor?

    The advantage of an infra-red sensor is that it can measure at a distance. If you wish to measure the temperature of transistors or resistors then infra-red is very convenient. Thermocouples are likely to be more accurate but they conduct heat away from what is being measured. How would...
  7. duke37

    Photoelectric Switch controlling a 12V DC Motor.

    If the battery voltage collapses when on load, the relay will drop out and the battery voltage will recover, the relay will energise again and so on. Make sure the battery is charged and in good condition.
  8. duke37

    Thermometer accuracy..sensor?

    It measures infra-red radiation not HEAT. Radiation is dependent on temperature^4 and the emissivity. Shiny metal surfaces have very low emissivity which is why heat sinks are often black. The device has a laser to do something, perhaps it measures the return signal and calculates...
  9. duke37

    Help with inverter

    You will need to give much more information. 1. What is the DC source? 2. How much power? 3. Output AC or DC? 4. If AC, what frequency and waveform? 5. What output voltage? 6. Does it need to be stabilised? 7. What is wrong with a chip? 8. Do you need isolation between input to output...
  10. duke37

    Help with circuit

    The first op-amp is a voltage follower with a high input impedance and a low output impedance so its output will be very similar to what the potential divider would give with no load. The second op-amp is a Schmitt trigger, but you know how that works. The diagram would be neater if you...
  11. duke37

    Switch on load only when alternator is running?

    You need an accurate voltage reference and a comparator. The easiest way is probably to use an LM3914 chip which has a reference and will drive a led display in either bar mode (like a thermometer) or in a dot display. By setting to a bar display and setting the sensitivity to make the bar...
  12. duke37

    3V to high voltage inverter

    I have a book - remember them. Unfortunately when I tied to look up the transistor again it wasn't there. I will have to get a new pair of glasses. The circuit you show has so many faults that you should start again. In particular, turns ratios will need to be recalculated and matched to the...
  13. duke37

    Filter Questions

    The 555 will produce an output going from 0V to 9V. The gain of the op-amp is 2 so that the 741 would need a positive supply of at least 20V. Try attenuating the signal from the 555 by about 4. I am not used to dealing with a 555 but shouldn't there be a capacitor on the discharge pin...
  14. duke37

    Increasing output of fixed V-Reg

    The diodes should be connected in the lead which goes to ground and should be forward biassed. Each diode will drop about 0.6V. If you need more voltage than this, you may be able to find a suitable Zener diode. I recently wanted more than 5V to drive a transistor radio and used a red led...
  15. duke37

    Help with an R2-D2 LED Circuit

    It did not work in simulation, it oscillated at 10MHz. I wonder what would happen if an extra stage were added bringing the phase back to the two transistor circuit. If you want a walking output, use a 4017 Johnson counter
  16. duke37

    Increasing output of fixed V-Reg

    The current in the tail of the regulator is not defined so a resistor can not be specified. A voltage divider with a larger current than in the tail can be set better. Your example indicates about 5mA tail curent. I have found a similar value with a 7805 regulator. A couple of forward...
  17. duke37

    Help with an R2-D2 LED Circuit

    The resistors need to be selected to get the DC conditions right so you will need to increase the capacity to lower the frequency. Doubling the capacity, halves the frequency.
  18. duke37

    12 volt voltage "clamp?"

    You could leave the internal resistors in place and add an external resistor to drop about a volt, say 4 ohm.
  19. duke37

    ESD and Robotics

    To stop getting a shock from the chassis, you need to earth it to ground so that it at the same potential as the operator. 12V or 9V will not give a shock. I expect that the voltage is derived from friction. This is quite common with plastic carpets in a dry atmosphere. The spark which...
  20. duke37

    Help with an R2-D2 LED Circuit

    They should all do but the 2N2222A is best.
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