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  1. (*steve*)

    Need help designing a resistor sequencer.

    You really need to test 3 things. Firstly that the 555 is oscillating. Secondly that the 4017 is correctly changing state. Thirdly, that the resistance is changing. I guess there is a fourth, that the change in resistance effects the circuit in the desired manner. You started at the last...
  2. (*steve*)

    how to reduce the current without changing voltage for charging a 9 v battery??

    Yeah do what I said and measure a across the resistor with your multimeter on a voltage setting.
  3. (*steve*)

    how to reduce the current without changing voltage for charging a 9 v battery??

    Try a 68 ohm resistor and measure the current through the resistor AND the voltage across the battery (do you have 2 multimeters?). Alternatively, measure the voltage across the battery and then across the resistor and use ohms law to determine the current. Monitor this and let me know what...
  4. (*steve*)

    Electronics Design Process

    Another step I missed is "research". You may have to do this even before you determine the requirements because you may not understand what the requirements might be. More often you may need to do research to discover some alternate approaches to solving a problem where you are unable to...
  5. (*steve*)

    Need help designing a resistor sequencer.

    Another reduction would be to use an 8 pin microcontroller to drive the 4066 and have 4 resistors. You could (with appropriate resistor selection) have 16 values of resistance.
  6. (*steve*)

    how to reduce the current without changing voltage for charging a 9 v battery??

    What is the open circuit voltage of your 9V adapter? What voltage is marked on those rechargeable batteries? 8.4V? You can charge those batteries with just a resistor to limit current but you risk damaging them.
  7. (*steve*)

    how to reduce the current without changing voltage for charging a 9 v battery??

    A proper charger is best.
  8. (*steve*)

    Battery doesn't power microcontroller as expected

    Does it work when you use some other power supply?
  9. (*steve*)

    Microcontroller project for my pool pumps

    You're right, there is not much information about that contactor. I tend to lean toward the argument that you have insufficient power at 24VAC to close both of them. Have a look here to see the correct way of using a transistor to switch a load. The way you have drawn your circuit, you could...
  10. (*steve*)

    Need help designing a resistor sequencer.

    The 4066 is a switch (actually 4 of them) designed to allow you to switch things (like resistors in your case) in and out of a circuit. A LED sequencer simply provides power to some devices (in this case LEDs). Unless your circuit has the resistor connected to a power rail (and the right one...
  11. (*steve*)

    240V ac LED bulb failure

    Here they are! Cheap ones are now 2 for $6. The earliest ones I bought were 2 for $15. The price keeps on dropping. Soon they'll be too cheap to bother stocking!
  12. (*steve*)

    Need help designing a resistor sequencer.

    What are the values of R1, R2, and R3? The 4066 has an internal resistance which may be significant if their values are low. Do the two circuits (the sequencer and the one where the resistor is being replaced) share a common ground? What is the supply voltage for the circuit not shown here...
  13. (*steve*)

    Need help designing a resistor sequencer.

    Please upload your image here. I looked at your image just after you posted the query but because the third party site makes it difficult to return here I could not post my reply (which I have since forgotten, but at least I have found your thread again)
  14. (*steve*)

    Microcontroller project for my pool pumps

    Firstly, please upload your images here. It can be a pita on a mobile platform to view images on Third party websites which fsck about with exciting their pages. Secondly, I note you have not tried what I suggested in my first post. Thirdly I note you don't have any base resistors and only...
  15. (*steve*)

    Large Wire Buzzer game

    Firstly, the copper tube has a very low resistance. Secondly, batteries of different types in series is a bad idea, and you're right in thinking the capacity may be too low. I would suggest an SLA 12V battery, but the battery you mention sounds fine. The buzzer is not a real problem because...
  16. (*steve*)

    Mosfet equallent

    Look up the datasheet for this device. Then determine which parameters are most important in your circuit. Then look for devices (digikey can be useful here) with specs which match or exceed your requirements.
  17. (*steve*)

    Digital circuit question help.

    Almost... I assume the 2^12 was a typo. And while there are 65536 values, one of those is 0, so what is the max value? And can you have fractional values? And finally, yes, the second question is the first in reverse.
  18. (*steve*)

    playing around with a current sink.

    Sure, I can draw a schematic tomorrow, but basically the 100ohm resistor is connected in series with the output of the constant current and then between this and ground is an emitter follower biased so it does about half the available voltage across the transistor. The signal is AC coupled to...
  19. (*steve*)

    Electronics Design Process

    An example of a "step 5" task might be the selection of an op amp. Perhaps the circuit requires a certain slew rate, or input offset, our perhaps it is completely non-critical. In the former case you may have a particular device in mind but maybe there is some pressure to use a cheaper part...
  20. (*steve*)

    Electronics Design Process

    Good point. You may even break down some of these "hard" modules into smaller parts. The are a lot of other things you could put in there if you wanted. You may have to consider thermal issues, noise, places where high tolerance parts are needed, test points, ease of maintenance...
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