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  1. BobK

    measuring signals above 1MHz

    I would expect so. And there should be a selector or CH1 or CH2 as well. And a triggering level control. Bob
  2. BobK

    measuring signals above 1MHz

    Well, then is triggering set to internal and CH1? Bob
  3. BobK

    "Has it got the Cobalt?" (story)

    My first job, after grad school was working on a COBOL compiler for NCR corporation, so I got it. :p Bob
  4. BobK

    Buying ICs off of ebay - I think I finally learned my lesson

    Yes, that is the voltage range you can put on the + and - input pins. Bob
  5. BobK

    Buying ICs off of ebay - I think I finally learned my lesson

    You need a rail-to-rail comparator. Microchip makes some good ones. http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11011&mid=11&lang=en&pageId=79 Bob
  6. BobK

    I need project ideas

    An alarm or announcer come to mind. Bob
  7. BobK

    measuring signals above 1MHz

    Sounds like your scope is not triggering reliably. You appear to have the signal generator hooked up to channel 2. Is triggering set for CH2? Bob
  8. BobK

    V-Reg Board for Breadboard use

    PICs are not at all sensitive to supply voltage. Most 5V PICS will run down to 2.5V, and the special low voltage ones down to 1.8V. Bob
  9. BobK

    Which PIC to pick? Could use a few pointers.

    For 16 LEDs I would not bother with multiplexing, which makes the code a lot more difficult. Use a big enough uC to drive each segment separately. A 28-pin should do for everything. Bob
  10. BobK

    Buying ICs off of ebay - I think I finally learned my lesson

    What was your supply voltage? The inputs can only go from 0 to Vcc - 2.0V, if you exceeded that range, anything might happen. Also, these are open collector. Did you have a pull-up for the outputs? Bob
  11. BobK

    Voltage to current converter circuit

    I don't see any disagreement. I said the actual power was 3W which is the same as you came up with. bob
  12. BobK

    A few beginners questions

    The measurements you are getting are not correct. They are impossible. Stop looking for reasons for them until you are sure you are measuring correctly. I will bet that if you carefully check the meter setting and position of the probes, you will not be able to reproduce your incorrect...
  13. BobK

    measuring signals above 1MHz

    You need to use internal triggering and set a trigger level that will make the display stable. Bob
  14. BobK

    Electricity and Math

    You need to know how much current the motors draw. Then you need a power supply that can provide more than 4 times that. It is that simple. If the power supply voltage is dropping from 12V to 6V, then it is not capable of providing the current needed by the motors. Actually, with motors, it...
  15. BobK

    Voltage to current converter circuit

    That is really meaningless, it will see different things at different points in the waveform. The voltage and current will be out of phase. I did a simulation and the peak instantaneous output power was 10W. The average power was 3W. This is with a 20KHz 1A peak sine wave output. Anyway...
  16. BobK

    A few beginners questions

    Most likely, it was. Because you actually had the meter set to read current instead of voltage. Does your meter have a different socket for the + lead when measuring current? If it does, and the lead was in the current socket, then the multimeter would behave that way even if you had it set...
  17. BobK

    Smoke detector mystery

    Not sure what you mean here. It is the only one that I have externalized the battery on, so yes. And it works fine with the same battery in the unit. No trauma to it. Yep, I used wire staples, but they have a good plastic insert so the wire is not scrunched or pierced. It is connected to...
  18. BobK

    Voltage to current converter circuit

    Unless the inductor is reacting with something other field, the inductive reactance will not result in any power usage. You only need to worry about the 3 Ohm resistance for power. I would think an audio amp capable of putting 1A into a 3 Ohm load would work okay. Bob
  19. BobK

    A few beginners questions

    Your meter might not be good at measuring resistance below 1 Ohm. Also, your resistor is obviously heating up (as evidenced by the burn marks). This will change the resistance. Bob
  20. BobK

    A few beginners questions

    Well, that is the correct way to measure. You really need two meters so that you are reading both the voltage and the current at the same time. It is not possible to get such different current through the same resistor at the same voltage. Bob
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