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  1. BobK

    2 relays with a shared common

    The relay will activate at some voltage below 12V. It is guaranteed to be on at 12V, but the minimum voltage is not normally specified. 5V will probably not do it. But I question your assumption. If a bulb is being varied by voltage, putting the relay coil in parallel to it will affect the...
  2. BobK

    Protection of Lithium Batteries

    Protection circuitry normally is applied to rechargeable cells rather than primary cells. You can put 2 in series then parallel the two pairs, as you suggested. Nothing else is necessary. Just be sure the cells are at the same state of charge when connecting them. Bob
  3. BobK

    Chassis mount 10W resistor value

    Does it likely have 100V+ across it? If not, 2.5K 20W would make no sense. Bob
  4. BobK

    What is the proper way to use 1 cell lipo batteries in parallel?

    3 12Ah batteries in parallel can be treated just like one 36Ah battery for the purpose of charging. Use a BMS suitable for a single cell of that capacity. Bob
  5. BobK

    How is it that so many wireless signals

    The simplest means of having different signals available in the same area is by using different frequencies of radio waves. Think of a radio being tunable to different stations. With cell phones, because there are so many of them, this becomes impractical. One way to get around it is ti is...
  6. BobK

    SuperCap Charging and Delivery System using Solar Panels

    To get 300mA at 5V will require about 600 mA at 2.7V. At this rate, your 900F capacitor loses 1 V in 25 minutes. And as it loses voltage, the current needed increases. Which means they will not power your device for one hour at its continuous draw. As you have been told, use a battery...
  7. BobK

    SuperCap Charging and Delivery System using Solar Panels

    Series or parallel, they will store the same energy. Your explanation contains no numbers so I cannot evaluate whether it is workable or not. It sounds to me like the circuit will draw some low amount of power continuously and then bursts occasionally (when transmitting data perhaps?) If...
  8. BobK

    Multiple AC inputs relay (light PLC)

    I would use a microcontroller and use optocouplers to translate the inputs. You could use capacitors to limit the current to the input of the opto. Bob
  9. BobK

    what motor

    Gearing is an amazing thing. This is the motor I used on a prop I built, which was an oversized music box with a Barbie doll spinning on top. It is 3V and 20mA and is quite powerful enough to spin a platter with some soap samples. This one is 30 RPM, they come in many speeds. 9V battery is...
  10. BobK

    12V power supply

    The question is why are you using a 12V transformer to get 5 and 3.3V? A 6V transformer would be better. Bob
  11. BobK

    LiPo Battery on use while charging

    If there is a charge indicator, it could tell you. Otherwise, you would have to break the battery connection and monitor the current going in / out of the battery. Bob
  12. BobK

    LiPo Battery on use while charging

    It is nonsense. A battery cannot be charging and discharging at the same time, the current flows in only one direction. So, if you have a power supply capable of providing the charging current and the operating current, the battery cannot tell if the power supply is powering the device or not...
  13. BobK

    Class AB Power Amplifier Design

    Mosfets do not have a very well controlled Vgsthreshold, so it you cannot bias the output stage the using two diodes like you can with BJTs. A pot to adjust the voltage between the two gates can overcome this problem, but it must be set manually for each one you build. Bob
  14. BobK

    design of short circuit indicator using neon for domestic distribution board

    Your description of what you want is a bit vague, but I will try to fill it out with my guess. I think what you are saying is that, after a breaker trips, you would like a circuit that comes after the breaker, monitoring the resistance of the load and indicating whether the fault condition...
  15. BobK

    hall sensor and ssr

    Tell us what hall effect sensor and what SSR you are using and we might be able to do that. Bob
  16. BobK

    Pic interface with sensor

    You should be able to contol the pulse width to within 1usec easily. Use a crystal to nake it accurate. Bob
  17. BobK

    Pic interface with sensor

    No, if using an N MOSFET the drain is connected to the low side of the load and the high side of the load is connected to 0.65V. Source is connected to ground. Use a logic level MOSFET and you can drive it directly from the PIC. Also choose a PIC that has enough I/O pins so you don’t need an...
  18. BobK

    Explain why DMM reads 00.0 on negative side of circuit

    Are you measuring Ohms on a powered circuit? That is a no-no. Bob
  19. BobK

    Solder sucker

    I also would like to have a store that stocked common parts for emergencies. But they ain’t coming back. It just isn’t economically feasible. Bob
  20. BobK

    Solder sucker

    Have you tried the internet? It is really amazing. Bob
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