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  1. BobK

    Newbie Question: 12v led ?push button latching switch

    If I understand you correctly, you want to use the switch in a place where it is not acting like a power switch but still have the LED light. You need to tell us more about the switch and the application. Bob
  2. BobK

    Transistor Help

    See here, for how to use a transistor as a switch: https://www.electronicspoint.com/resources/using-a-bipolar-transistor-to-turn-a-load-on-and-off.30/ The problem is where you are putting the transistor. It needs to go between the negative power lead of the servo and ground. You also need a...
  3. BobK

    Microcontroller debugging

    Use the simulator to debug timing problems Bob
  4. BobK

    Diode help

    You replacement is good on reverse voltage (1000V vs 400V) and current (3A vs 3A) and forward voltage of each is 1V at 3A. But the original is a fast recovery type and the replacement is not. This could be a problem. Look for a fast recovery diode that has the reverse voltage and current at...
  5. BobK

    Power output from a mobile phone aux socket

    Use a powered speaker, i.e. one with an amplifier built in. Bob
  6. BobK

    Radio question. What replaces the LC circuit?

    When a radio is digitally tuned, a crystal provides a base frequency and a phase locked loop multiplies this frequency by a different number to tune each station. Bob
  7. BobK

    Powering my IC

    Or use one of the many 5V USB chargers you probably have lying around like most of us. Bob
  8. BobK

    Forklift LiFePO4

    contactor = heavy duty relay. Bob
  9. BobK

    Learning Unijuctions

    Nice. I guess you would call that a spike. Bob
  10. BobK

    12V 2A plugpack burnt out while powering small led strip

    The strip has cutting points at every 3 LEDs. Hopefully you cut it in the right place. A 1.5m strip will require 600mA at 12V. It should not have destroyed a 2A power supply if connected correctly. I suspect you had a short. Bob
  11. BobK

    Learning Unijuctions

    Look at where you are measuring current. There should be a large pulse of current through the LED when the UJT fires seeing as the capacitor discharges very rapidly. Bob
  12. BobK

    Two mic's, one CB

    What kind of microphones? A diode is definitely not the right answer, it would cause lots of distortion. Resistors would work, but the value would depend on the kind of mic and the volume of each mic would be reduced by 1/2, which may not be a problem if there is a microphone gain control on...
  13. BobK

    Is it a "transfer switch"?

    Easiest way, if you do not know much about electronics, is to use a normally closed relay. Powering the relay turns the light off. Removing power to the relay turns the light on. You can also do the same with a transistor for a small bulb or an LED. Bob
  14. BobK

    Component Storage

    I use the multi-drawer cabinets like the picture Dave posted. I have a whole cabinet just for resistors and one for capacitors. Each drawer contains only a few standard E12 values. Bob
  15. BobK

    LED Circuit Problems

    If you have 30 LEDs with a forward voltage of 3.3V each wired in series, you need 99V to run them at their rated specs. You can hook them up to your 6V battery and they will not even light at all. And 20mA is not going to melt any wires. You need to put them in parallel with each LED having...
  16. BobK

    Question about building small device with touch sensors

    It's what goes between the sensor and the USB cable that is complicated. You can buy a USB GPIO board that has analog inputs, this might do the trick. Bob
  17. BobK

    How can I use a sensor output (0-5VDC) to actuate power disconnecting to another device?

    6 batteries in parallel each providing 10A is 60A, not 120A. So, if the sensor is outputting these discrete levels, you simply need a comparator set at somewhere between 1V and 2V (1.5V seems reasonable). To do the logic. You need one or more robust MOSFETs to switch 60A. Your last...
  18. BobK

    How can I use a sensor output (0-5VDC) to actuate power disconnecting to another device?

    How are we to interpret this sentence? If it take it literally, the sensor will output only one of the those three voltages, with nothing in between. But I suspect that it actually can output anything within the range and probably outside the range of 0.5 to 2V. Which is correct? Bob
  19. BobK

    Audio Circuit too sensitive

    You have to make sure the signal going in is in the right range for the amplifier. Are you using a microphone input? They are far more sensitive than an AUX input or LINE input and should not be used except for a microphone. Bob
  20. BobK

    How hot is too hot for a phone?

    If your science fair projects involves heating up phones until they fail, this could be very dangerous. A likely failure mode could be an exploding battery. Bob
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