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  1. crutschow

    Strange battery behaviour in portable radio?

    Yes. It means the one battery has slightly less capacity than the other two and completely discharges first. Yes. For a nominal 0.15v (150mA) drain the battery life would be a maximum of (bat mAh / 150). Thus a 2500mAh battery would last for about 2500 / 150 = 16 hours maximum, which is...
  2. crutschow

    Strange battery behaviour in portable radio?

    That would be the safe thing to do. The lower current input may have a fuse in the multimeter for protection. Yes.
  3. crutschow

    Is this MOSFET right for this voltage?

    That MOSFET has a 100V max rating so is not suitable for a 100.8V battery. The MOSFET you use should have at least a 125V rating with the same or less on-resistance value.
  4. crutschow

    Strange battery behaviour in portable radio?

    I think that's correct, but you seem to be talking about three leads which is confusing. The red meter lead goes to the lifted battery terminal and the black lead goes to the battery connection on the radio. What is the black lead you mention?
  5. crutschow

    Strange battery behaviour in portable radio?

    Then AA's would only operate the radio for about 4 hours, at best. Can you use your multimeter to measure the actual radio current (put multimeter in series with the battery connection to the radio).
  6. crutschow

    Need a rectifier schematics

    That likely explains it Long live the decibel !
  7. crutschow

    Need a rectifier schematics

    Does the AC source need to share a common ground with your DC output? That determines whether you can use a bridge rectifier or not. What does CC mean? It can't be constant-current if you want a voltage output.
  8. crutschow

    reversed variac

    Within limits, you could use a buck-boost switching regulator to give a constant output voltage from a variable input voltage. The power out will always be somewhat less than the power in, of course.
  9. crutschow

    PWM shielding

    Depends upon the level of shielding you need. What "issue" are you concerned about?
  10. crutschow

    Instantaneous charge state of supercapacitor detection

    Can't you just use three comparators?
  11. crutschow

    Preventing a possible 12v short circuit

    If you aren't aware, the lines in the schematic represent wire connections, and a dot on the wire indicates the two wires are connected together. The two wires can be connected together at any convenient point in the physical circuit (such as a relay terminal).
  12. crutschow

    Preventing a possible 12v short circuit

    I think that's essentially that same circuit as my post #12. The diodes in my circuit are to prevent contact arcing and erosion from the high reverse transient voltages otherwise generated by the relay coil and actuator inductances.
  13. crutschow

    Preventing a possible 12v short circuit

    Sorry I didn't properly understand your requirements, thus my incorrect previous response. You can use two 12Vdc SPDT relays in a bridge configuration, activated by the timers to control the actuator as shown below: It will not cause a short even if both relays are on at the same time (it would...
  14. crutschow

    Preventing a possible 12v short circuit

    If both timers are on at the same time, there won't be a short if they are applying power from the same 12v supply.
  15. crutschow

    Sensing 0-10 RPM of a shaft continuously

    To convert the pulses to RPM you can measure the time between pulses with a micro, and then do the math to generate the RPM value. For example, if you have 10 pulses per revolution from your sensor, and you measure the pulses as having a 0.5 second period, then the shaft speed is 0.5 / (10*60) =...
  16. crutschow

    Replacing electrolytic cap with non-polarized a mistake with tube radio?

    A black band around a non-polarized cap can indicate which wire is connected to the outside foil on a film capacitor. This can be important to know when using the cap in high frequency circuits. For example, if the capacitor were being used as a high frequency bypass to ground, you would...
  17. crutschow

    Replacing electrolytic cap with non-polarized a mistake with tube radio?

    If the non-polarized cap had the same capacitance and voltage rating as the original, then that should cause no problems, such as blowing the tube filament.
  18. crutschow

    Why use diodes in this circuit

    There are few motors that aren't. ;)
  19. crutschow

    On/Off switch MOSFET based

    Why is R3 scribbled in?
  20. crutschow

    Why Do DC Inverters Damage Items?

    A surge protector won't improve the waveform from the inverter. It might be cheaper to see if you can find a heating pad without any electronics (if they still make them).
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