Search results

Search Forums New Posts
  1. Audioguru

    How does a multimeter's continuity function work?

    My Fluke meter uses 0.2V for resistance testing and about 2.5V for diode testing which is not enough voltage to light modern white, blue and green LEDs.
  2. Audioguru

    How to get 3.3 V from a charged LiPo battery?

    A single Li-PO cell is 4.2V when fully charged and its charging current has dropped low, 3.7V about halfway during a discharge and 3.2V when it must be disconnected. If you do not disconnect it when its voltage is 3.2V then the voltage will go lower and ruin the battery. A Li-Po cell that has...
  3. Audioguru

    Questions battery AA and AAA and battery charger

    I do not know what you are saying. "The battery from the manufacturing" might be that you are asking about if a battery is stored without a full charge for 10 years and it does not hold a charge then will it be replaced? My Energizer 9V Ni-MH battery was stored for about 8 years and it did not...
  4. Audioguru

    Questions battery AA and AAA and battery charger

    It was an old 9V Ni-MH battery. Energizer Battery Company who made it says that new Ni-MH batteries should be charged every year is they are stored. I have an Energizer 9V Ni-MH battery in a VU sound level meter that has been trickle-charging for about 8 years and it still works. I bought it at...
  5. Audioguru

    FM transmitter circuit connection

    Broadcast band FM radio uses equalization called "pre-emphasis" to boost high audio frequencies for transmitting and "de-emphasis" to cut the high frequencies back down to normal for receiving so that hiss picked up is reduced. All FM radios have de-emphasis so your simple transmitter that is...
  6. Audioguru

    Questions battery AA and AAA and battery charger

    I said that I stored a Ni-MH battery without use and without charging it for a number of years and it did not work. I also said, "Energizer's Ni-MH battery Manual says a Ni-MH battery will last 5 years or less. They say to store them in a cool dry place with a charge. The new ones will hold a...
  7. Audioguru

    On off for headphone line

    I am not going to draw a simple switch, I am too busy today.
  8. Audioguru

    On off for headphone line

    Obviously you do not understand what your switch does. The earphones will then be connected in series and out-of-phase with each other. Low frequencies usually play in mono so they will be cancelled.
  9. Audioguru

    In line switch with led indicator

    An ordinary switch is designed for 120VAC/5A electricity, not low voltage and low current audio. Its contacts are silver for 5A and they soon tarnish and rely on the high voltage and high current to burn away the tarnish. With audio the silver contacts soon tarnish then do not work. Switches...
  10. Audioguru

    Need Help With Li Ion Battery

    You need to know how loud you want the speakers to play then calculate how much power the amplifiers must provide. The datasheet for the amplifiers will say the battery voltage for the power you need. The voltage will say how many battery cells you need. Then you can calculate the size of the...
  11. Audioguru

    On off for headphone line

    Since the headphones output is completely separate from the TV speakers then when you do not use the headphones then why bother to switch them off? It will take many years to wear them out if they are not disconnected with a switch.
  12. Audioguru

    FM transmitter circuit connection

    We have all seen that very old circuit using obsolete transistors in metal cases. I wanted to see the project at Circuits Today but my browser said "Beware, they have a security issue". Of course a modern headset uses an electret microphone that will not work in that simple circuit. A stereo...
  13. Audioguru

    240VAC Transformer based 12 VDC PSU - Problem

    The capacitor is said to be a 10uF tantalum or a 47uF electrolytic. I use the electrolytic but not in a freezer.
  14. Audioguru

    FM transmitter circuit connection

    Your schematic is so small that we cannot see its details when enlarged. Your parts are WAY too far apart. They are supposed to be close together at the Very High Frequency of the FM band. your transistors in an old metal can look like they are 40 years old. My FM transmitter has many more...
  15. Audioguru

    Automatic Street Light using LDR Project ( Need someone's assistance)

    LDRs are not used in solar garden lights anymore because they get sunburned and corroded. If they are in a streetlight then bird droppings cause the light to remain turned on all the time. My city replaced all the streetlights with LED ones and each has a radio-controlled circuit, you can see...
  16. Audioguru

    Switch needs to remain on for certain time

    Some children's toy dragons have a small slim pcb with a blob-on-board that blinks two LEDs 32 times (about 15 seconds) then shuts off. Its 4.5V outputs can be added and fed to a logic level Mosfet.
  17. Audioguru

    Sound activated light

    A microphone is not wanted and is not needed because the sound signal is in the cable that is fed to the prop. The maximum allowed reverse voltage for an LED is only 5V so it needs to have a reversed diode parallel to it. The typical current for an ordinary 5mm LED is 20mA then with a 300 ohm...
  18. Audioguru

    Battery advice for size and weight sensitive project

    The voltage of a discharging capacitor drops quickly at first, then it levels out when it is almost dead. The voltage of a discharging battery stays up, then drops quickly when it is almost dead. Don't you want the fan to run properly?
  19. Audioguru

    Mini wind turbine to light an LED

    The schematic with the transistors shows no switch. It has a diode to prevent the capacitor from discharging into the slowly turning generator. The voltage from the generator must be higher than the diode voltage plus the LED voltage. Where did you connect your switch? Please post your schematic.
  20. Audioguru

    Battery advice for size and weight sensitive project

    I buy E-Flite and Thunder Power Li-Po batteries from my local hobby store. They are American companies, not Chinese. The Thunder Power batteries can supply pulses of current that are 140 times their mAh rating, or 70 times continuously. There is a Japanese brand of Li-Po that is recommended, but...
Top