Search results

Search Forums New Posts
  1. duke37

    Super Capacitor\Cell Battery Voltage meter

    The LM3914 has ten comparators a reference voltage and is designed to drive leds, either as a dot or a bar. As kpatz says, you will need a boost convertor and should consider how the capacitor voltage will hold up when you load it.
  2. duke37

    capacitor and inductor

    In #3 I suggested consider energy. If the capacitor is to be increased in voltage, it will need to be supplied with energy. To raise the voltage instantaneously it will need infinite power. This is not available here.
  3. duke37

    Check my wiring scheme please

    A thermocouple has a hot junction and a cold junction. In your case the hot junction will be the end of the thermocouple. The cold junction may be at the measuring device and perhaps held at a constant temperature, in this case, the cable will be compensating lead with similar properties to the...
  4. duke37

    Transformer

    I know of no general rule. A high frequency is beneficial since fewer turns can be used so more insulation is possible Many turns mean little insulation and very fine wire so high resistance, also winding capacitance becomes important. Look at the construction of TV line output transformers...
  5. duke37

    Check my wiring scheme please

    You should not shorten the thermocouple if has a metal sheath. It will be sealed to stop moisture getting in. If it is just two wires, then you can chop it down but getting a good connection to chromel/alumel can be difficult due to the surface oxide. Why not just coil up the surplus?
  6. duke37

    Op-Amp Gain ?

    I agree with a gain of 1001 at low frequency, near enough to 10^3. There is no way that circuit can give a gain of 10^6.
  7. duke37

    Connecting AC and DC grounds on breadboard

    120V can kill you but only once. Do not put anything over 24V on a breadboard. With 120V buzzing about any wiring error or even a poor contact could fry both you and your computer. Digital, power and analog grounds should be separate and then tied together at a common point.
  8. duke37

    resistance monitor

    I still do not understand what you are trying to do. Give us a diagram of what you have and another of what you want to do. In order to check if there is a break in the cable you could put 24V on the far end and use the received voltage to light a led or switch a relay. I do not follow what an...
  9. duke37

    resistance monitor

    We will need more information. Is the circuit isolated from anything else? What current can be passed through it? What accuracy do you require? I do not like relays but it can probably be done with a power supply, a couple of relays and a couple of resistors.
  10. duke37

    Connecting 12v dc motor to a rc circuit car

    A two pole changeover relay will do what the normal H-bridge does i.e. change direction but will need a switch to turn power on and off. This could be done with a mosfet. The relay would be unenergised in one direction and if this is chosen to be the most commonly used, then relay power...
  11. duke37

    Connecting 12v dc motor to a rc circuit car

    Kris is throwing me in the deep end again ! First, you need to know the type of motor that you have. The most common for this application would be a permanent magnet field with carbon brushes to feed the armature. This motor,if turned, will act as a generator with an output voltage...
  12. duke37

    Explain the principle of operation of a synchronous generator with the aid of calculations.

    Somewhere I have a book 'Aternating current machines' by Kay. I can understand most of it. Edit or Say Edit2 Alternating Current Machines by M.G.Say 1976/1977 ISBN 0 273 36197 X
  13. duke37

    Polarity Protection

    I was thinking of using this on an electric fencer. These are used with a variety of batteries at various voltages. The most common battery is a 10V lead acid battery i.e. a tractor battery with a shorted cell. It is easy to clip the leads on the wrong way. My brother puts a red disc over the...
  14. duke37

    Polarity Protection

    Polarity Protection I was thumbing through my notebook and came across this circuit drawn about 25 years ago. I have not used it. The circuit uses a MOSFET in a reverse connection, it should need no current to drive and give a very low voltage drop. The diode I assume is the diode inherent in...
  15. duke37

    3 Way cross overs.

    Just try it. From what I remember of stuff I read about 50 years ago.the crossover should be designed for the drivers used since they are not simple resistive loads. Phase difference and driver location should be considered. Two speakers in parallel will be nominally 4 ohm.
  16. duke37

    Voltage converter 120V to 220V

    There is a single 270µF 220V reservoir capacitor so it is unlikely that the power supply can be switched to 240V. Those that can be switched have two capacitors in series which can be charged with a bridge rectifier for high voltage or from a voltage doubler for lower voltage. Even if you get...
  17. duke37

    AC Analysis common emitter configuration

    Gain of Q1 The simplified calculation assumes infinite transistor gain and neglected re. You calculated re as 20R so the emitter resistance is nearer 20 + 150 = 170 Gain calculation = 1200/170 = 7.0 which is very near the simulation of 6.9. To get even closer, you could look at the effect of...
  18. duke37

    Feedback bronze wall

    I await your pictures and maybe a diagram on what you intend. My initial thought is that it would be simplified if you used magnetic material i.e. steel. The panel could then be vibrated with a magnetic field, similar to a loudspeaker. With tight enough coupling the system could be made to...
  19. duke37

    ground pour under component

    Coppe pour - that just shows my ignorance ! If the component has a plastic skin, then it should be able to withstand 12V. A slight gap may be advantageous to allow more flexibility to take account of board flexing or expansion.
  20. duke37

    AC Analysis common emitter configuration

    I am not familiar with your // convention. All computer programs that I have used from algol onwards have just used brackets. To look at Q2 in a simplified way, the voltage gain is the collector resistor/ emitter resistor. The collector resistor is shunted by the load resistor, R11 so gain is...
Top