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  1. Audioguru

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    RC Li-Po batteries have three identical cells bonded together. The individual cells discharge voltages are not monitored, only the total discharging voltage. The cells are balanced charged where each individual cell is monitored. I think 3V per cell is too low and damage is being caused. 3.2V...
  2. Audioguru

    Looking to build mini pen light version of this flashlight:

    By twirling a lanyard, how does the motor generator in the flashlight spin? Do the magnets in the motor keep it pointing to the North Pole of earth? Then the motor will spin very slowly and generate almost nothing. How many hours of spinning allows the LED to light for a few minutes?
  3. Audioguru

    Looking to build mini pen light version of this flashlight:

    Nobody makes a 3V LED. They are anywhere from 2.8V to 3.6V and you get whatever you get. Nobody makes a "3V rechargeable battery" but one Lithium cell is 3V when dead and is 4.2V when fully charged. I have never seen an ebay lanyard light but I think it will be very dim and the lighting will...
  4. Audioguru

    how to prevent simple AA battery electromagnet short circuit/overheating

    Instead of adding a component that tells you the circuit is safe, why not design it to be safe and use common sense? Simply do not use a little AA cell or little 9V battery to drive the starter motor (it is an electromagnet) in your car.
  5. Audioguru

    Building switch between PC headphones and PC speakers. Can I combine the Grounds?

    Usually a headphones output has attenuation so the speaker level does not blow your head off. Headphones usually have the grounds connected together. Frequently speakers have each wire driven from separate amplifiers (bridged) so there is no ground wire.
  6. Audioguru

    Simple resistor overheat problem

    I found strings of LEDs thrown out because they were poorly made and had intermittent connections. All the LEDs were in parallel and somebody must have bought millions of them, tested all of them and grouped them into piles that had exactly the same forward voltage. So I did the same when I...
  7. Audioguru

    Simple resistor overheat problem

    Then why did you scribble "550"? if you use Paint program to make the schematic then you can clearly type words. Did you look at the datasheet for your LEDs and see that their absolute maximum continuous current is only 30mA? Here is part of the datasheet of a typical 5mm red LED:
  8. Audioguru

    Simple resistor overheat problem

    LEDs have a range of forward voltage. White and blue LEDs are from 3V to 3.6V. The average is 3.3V but all yours might be 3.0V or 3.6V. If you connect 3.0V and 3.6V LEDs in parallel then the 3.0V LED will hog all the current and be destroyed. If you connect three 3.6V LEDs in series then a 9V...
  9. Audioguru

    potentiometer

    Of course not. A variable inductor varies its inductance. A potentiometer varies its resistance. Guess what a variable capacitor varies?
  10. Audioguru

    RGB LED strip

    A speaker operates with AC. Most (but not all) LED strips operate from DC. Most LED strips use 12VDC but the output power of your amplifier determines its voltage that might be too low and the LEDs will not light or the voltage might be too high and it will destroy the LED strip. We do not know...
  11. Audioguru

    with or without silicon in driver of LED Light?

    Most of my cheap Chinese solar garden lights lasted only a couple of months because they were poorly sealed so I sealed them. Then the poor quality Ni-Cad batteries and LEDs rust away in a few months due to condensation. I have replaced the batteries with modern Ni-MH in stainless steel cases...
  12. Audioguru

    How to set amps to charge lipo batteries

    No, when the voltage reaches 4.20V the battery is still charging and is about 85% fully charged. The remaining 15% of charging takes a fairly long time because then the charging current drawn by the cell keeps reducing The cell is fully charged when the 4.20V charging current is about 3% of the...
  13. Audioguru

    How to set amps to charge lipo batteries

    I have a Lithium battery from an old cell phone. It has two cells permanently welded together on parallel since the battery was made. There is never one cell with some charge and the other cell with less charge which will cause an explosion if they are connected together. The two cells are...
  14. Audioguru

    New Product Prototype

    Yes, a 1000mAh battery can be charged at 1A. Get a high quality battery, not a factory reject or fake one sold on ebay.
  15. Audioguru

    How to set amps to charge lipo batteries

    Do Not adjust the volts and amps of a Li-Po charger circuit. The charger circuit is supposed to do it. Buy a charger that is made for your battery. Do Not use a cell phone "charger" that is simply a power supply for the charger circuit inside the phone. It is wrong to charge Lithium batteries...
  16. Audioguru

    Want to increase brightness of LED headlight

    An oscilloscope looking at the voltage pulses in a resistor that is in series with the LED shows pulses, not the average current that creates the light that you see You do not see the peak light of the high frequency pulses, the low duty cycle dims the light (that is how a dimmer works). The...
  17. Audioguru

    New Product Prototype

    A charging current of 1A (1000mA) is much too high for a little 150mAh battery. It should be no higher than 150mA so change the resistor (use 8.2k for 150mA) on the charging circuit. The charging circuit senses that the battery voltage is high enough (due to extra voltage caused by the high...
  18. Audioguru

    Want to increase brightness of LED headlight

    You should not put a capacitor in that switching circuit (the capacitor is a dead short to the high frequency) because it might burn out the Mosfet switch. You show a film capacitor, not a ceramic one. Its value is 10 followed by 4 zeros which is 100000 pF which is 100nF which is 0.1μF. On my...
  19. Audioguru

    Want to increase brightness of LED headlight

    The datasheet for the QX5252 IC shows only one rechargeable cell battery but you have two cells in series. How are you measuring the output current? It is pulses that a meter cannot see. Of course the input current is higher than the output current, the input is a low voltage and the output is a...
  20. Audioguru

    LED IR

    A photo diode is easily destroyed by a 9V battery. A photo diode has a very low output level so it usually feeds a high gain amplifier.
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