Search results

Search Forums New Posts
  1. BobK

    Need recommendation for rheostat or potentiometer

    The first one would do, but, be aware it is 6 inches long. The second (100Ω) is too high The third (2Ω) is too low Bob
  2. BobK

    Need recommendation for rheostat or potentiometer

    12V 2.5A. If you dialed it down to 6V with a rheostat (not potentiometer,) it would be 1.25A at 6V in both the fan and the rheostat. So the rheostat would need to be 15W minimum, probably 25W to be safe. That is going to be large and expensive. This one would be about right...
  3. BobK

    MOSFET PWM Circuit Not Working

    Yes you are, if you are using a 1N4001. The diode will carry the same current that the motor is drawing. Bob
  4. BobK

    MOSFET PWM Circuit Not Working

    The reverse voltage on the diode is the same as the voltage to the motor, so 12V is all you need. The problem is the current. If the motor came with a 250W supply, why do ypu expect it to draw less than 1A? Bob
  5. BobK

    Battery

    Be aware that the capacity is rated at some specific rate of discharge, often 20 hours, and the capacity can be much different at higher discharge rates. For example, if the battery is discharged over 1 hour, it will likely have less than 1/2 the rated capacity. Bob
  6. BobK

    Multiple mosfet driving

    You really need a push pull circuit to ensure that the MOSFETs do not stay in the linear region long. If you are using 10K and a single sided driver, it is probably dissapating mich more power than it should currently. Bob
  7. BobK

    Class A Amplifier

    Class A amplifiers are not good for power amps. You want AB or D. Bob
  8. BobK

    Automatic Batttery Charger Circuit Needed

    You don't necessarily have to charge them in series, in fact, this requires extra circuitry as well. I assume that you are talking about 12V lead acid batteries, then. What capacity and what charging current? Bob
  9. BobK

    Automatic Batttery Charger Circuit Needed

    Of course it is possible. But if you are going to go to all that trouble, why not make one that can charge all 4 at the same time? Bob
  10. BobK

    555 on/off circuit for 5v motor (w/ schematic)

    If you use the discharge pin you cannot get duty cycles of 50% or less. If you use the output pin to do the discharge you can. That is is why it is done that way. Bob
  11. BobK

    Etching first PCB problems - conducts between tracks

    Did you remove all the components before testing the resistance between tracks? Bob
  12. BobK

    Circuit Which Turn On The Light As A Response To A Specific Sound Sequence ?

    How far away is the phone?
  13. BobK

    Circuit Which Turn On The Light As A Response To A Specific Sound Sequence ?

    The difficulty of this project will depend a lot on the loudness of the triggering sound vs the ambient noise. It could be as simple as a bandpass filter, peak detector and a little bit of logic, or as complicated as a DSP (digital signal processor) doing an FFT (fast Fourier transform) to...
  14. BobK

    12 v to 48 v boost converter for 48 v electric bike

    A boost converter is not the same thing as an inverter. There is only a single coil, rather than a transformer and the output is DC (with ripple.) Bob
  15. BobK

    555 on/off circuit for 5v motor (w/ schematic)

    You can also improve the circuit by placing the transistor between the motor - terminal and ground. I.e. motor + to V+ motor - to collector emitter to ground This will reduce the voltage drop across the transistor to about 0.2V and make the transistor run cooler. Bob
  16. BobK

    Current/heat dissipation control in an R-L circuit

    For 1.2A you could go as low as 28AWG and you would need 49 turns. For 26AWG I get 79 turns. Bob
  17. BobK

    Simple resistor overheat problem

    Or by selecting the button for it above the edit box when you are typing in the message! Ω Ω Ω Ω Ω Ω Bob
  18. BobK

    Problems with composite video generation!

    Nice!
  19. BobK

    12vdc low amp to 120vac high amp flash/blink lamp inverter circuit?

    200W * 1 second = 200J of energy The energy in a capacitor is 1/2 CV^2 If V is 120V, C we get 200 = 1/2 C * 120 * 120 = 14400 C = 400 / 14400 = 0.028F = 28000uF And that is just to have enough energy if you could suck it all out over 1 second. With an efficient boost converter, say 80% you...
  20. BobK

    LED PSU board, wondering what it is..

    The capacitor in series limits current for AC just like a resistor would for DC. Bob
Top