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  1. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    If the copper traces on your pcb are too narrow for the high current then they will burn out like a fuse.
  2. audioguru2

    Two PCBs off of one power source

    I never use a breadboard. The connections are always intermittent. I quickly sketch a parts layout then solder the parts and a few jumper wires (that do not cross) on stripboard. Pin 2 and pin 3 of an MC34119 amplifier must never be grounded. They are supposed to have a filter capacitor to...
  3. audioguru2

    turnsignal and brakes

    The law that says you can't modify lights on cars is for safety, not for cops. You replaced bright wide-angle incandescent light bukbs with dim, narrow-angle LEDs. Then you want to make them dimmer by flashing 1/3rd of them. I hope you won't be driving in front of me at night in bad weather.
  4. audioguru2

    Ft of the transistor

    Hi Walid, Think about a child on a swing. A small push at the correct moment makes it swing higher and higher. It can easily swing higher than the bar that holds it. If you keep adding small pushes then it goes higher and higher. The bar of the swing is the supply voltage. The swing resonates...
  5. audioguru2

    Problem in an H-Bridge

    The TIP127 needs a base voltage of about 22V to turn on and 24V to turn off. Your 9V battery and relay won't do it and are not needed. I modified your circuit so that the blue resistors turn on the TIP127 darlingtons and the red resistors turn them off. The resistors and darlington transistors...
  6. audioguru2

    Ft of the transistor

    It doesn't matter because the emitter of the oscillator can supply enough base current to the output transistor. Good point, Kevin. They measure the ft with a collector/emitter voltage of 20V and measure the high frequency hfe with 40V to reduce the transistor's capacitance so it has better...
  7. audioguru2

    white led

    The 3.9 ohms resistor dissipates only (1.25V x 1.25V)/3,9= 400mW. A 1/2W resistor would be extremely hot, a 1W resistor will be fine.
  8. audioguru2

    turnsignal and brakes

    Here in Canada it is illegal to modify the lights on a car.
  9. audioguru2

    turnsignal and brakes

    I thought that all cars need to have two or three brakelights and that the turn signals must be separate. With your idea if a brake light is burnt out and you turned on the turn signal flasher for the other side then your car would appear to have no brakelight.
  10. audioguru2

    Two PCBs off of one power source

    Hi Bruce, My MC34119 circuit uses a 100uF supply bypass capacitor but it will work with 10uF. I have some very small 10uF electrolytic capacitors that I removed from old electronic things. One wire of electrolytic capacitors is marked "-". It must not be connected with backwards polarity in a...
  11. audioguru2

    Ft of the transistor

    I simulated my FM transmitter and increased the value of its oscillator's feedback capacitor. It produces 11V p-p across a 75 ohms load which is 202mW RMS. The collector current has a peak of 95mA. The transistor's collector current drops to zero on each cycle. As I suspected it operates in...
  12. audioguru2

    BJT biasing formulas

    A transistor's output impedance is the value of its collector resistor. The collector resistor is the signal source and the capacitance of the transistor's collector plus stray capacitance forms a lowpass filter with it. If the value of the collector resistor is lower then the collector current...
  13. audioguru2

    Two PCBs off of one power source

    Silicone is a flexible synthetic rubber. Transistors and diodes are made from very hard silicon. Diodes have part numbers. RadioShack is not in Canada anymore and I can't remember which ones they sold. Use two 1N914 or 1N4148 small diodes in a glass case or use two 1N400x larger rectifier diodes...
  14. audioguru2

    hydroxy gas power supply/separating oxygen and hydrogen from water

    A Mosfet is completely different from a 2N3055 transistor. The circuit doesn't have anything to supply enough base current to a 2N3055 transistor for it to conduct the high current needed.
  15. audioguru2

    Problem in an H-Bridge

    Hi Ys, Your control signals A and B must be 0V as a low and +24V as a high. Where do they come from? The TIP122 NPN darlington transistors have nothing to turn them off. When one is turned on with a saturation voltage of 4V then the other one gets a base voltage of 4V and it also turns on. Make...
  16. audioguru2

    help......how to build line follower colour sensor

    The blue floor reflects blue light. The white line reflects all colours. If you use a red filter over the photo-detector then it will be very sensitive to the red from the white line and not sensitive to the blue floor. Use a red LED, not a blue LED. Also don't use an ordinary white LED because...
  17. audioguru2

    Two PCBs off of one power source

    Good. All battery-powered electronic circuits should have a supply bypass capacitor to keep a fairly stable supply voltage as the battery internal resistance increases as it runs down. The MC34119 amplifier might oscillate without a bypass capacitor when the battery gets a little used. Of...
  18. audioguru2

    Help!! My Door Alarm is not work?

    Brass, copper or even gold will conduct well for the hook. Wayar won't work. Use wire. It must have any insulation removed.
  19. audioguru2

    Two PCBs off of one power source

    The power dissipated in the resistors in your circuit is so low that I won't bother calculating it. Use 1/10W resistor for their small size if you want and they won't even get warm.
  20. audioguru2

    Ft of the transistor

    Hi Walid, My FM oscillator uses the transistor's alpha, because it is a common-base amplifier. A common-emitter amplifier needs to have some beta. An oscillator needs to have a minimum voltage gain of slightly more than only 1.
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