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  1. J

    does a 9V battery have a current limit?

    A heat sink will not increase the current. What that means is if you run it without a heat sink at it's max current it will blow up. Also, did you measure the battery voltage open circuit or under load?
  2. J

    does a 9V battery have a current limit?

    700mA sounds like a lot of current for a little 9V battery. How hot is the battery getting? Batteries have a internal resistance that will limit their output current. This internal resistance gets worse as the battery discharges.
  3. J

    can someone idiot proof this simple circuit?

    You could use a potential divider (potentiometer) and drop part of the voltage before it gets to the motor. That is by far the easiest route. Even if you dropped the full voltage across the resistor that is 12V * .06A = .72W That means a 1/2W linear potentiometer is all you would need and...
  4. J

    Pull Up Resistor

    Yes, it will be in either one of the two states forever(but it can change states, circuitry dependent), but it will never be floating.
  5. J

    step motor

    So it is a DC motor then? What are the ratings for the motor? Your best bet with a DC motor is PWM. How complex that will be depends on whether the motor needs to change directions. Again I am only assuming what motor you have because you really haven't told us yet.
  6. J

    C programming on PIC16F877A

    What header file do you think? Did you even look in the folder, I think this should be self explanatory.
  7. J

    C programming on PIC16F877A

    You would answer your own question if you looked at the header file included in the above code for your pic. Read again what I said and then go look at the header file. Prove it to yourself that the above is true. C:\Program Files (x86)\HI-TECH Software\PICC\9.83\include is where the headers...
  8. J

    step motor

    I will assume you meant 120VAC motor as 'classic' Then maybe a VFD would allow you to change the speed. I know they use them for three-phase, but I think there is some that will work on single phase. http://www.anaconsystems.com/text/opti_e2.html Your second option is to use a DC motor and use...
  9. J

    Pull Up Resistor

    It can have everything to do with a button or switch or nothing at all.
  10. J

    Hello Im new this is my first post, I have lots a questions.

    http://www.repairfaq.org/sam/safety.htm Here read this.
  11. J

    Hello Im new this is my first post, I have lots a questions.

    But only at the right voltage. As davenn said, you need high voltage to break down the resistance in the skin. What this means is that anything below 50V with normal dry hands will do zero damage to yourself. Also remember the golden rule of thumb, don't ever double dip. What this means is keep...
  12. J

    C programming on PIC16F877A

    I think you will find out though that the header file for your pic defines RA1 as PORTA bit 1. So in a sense your program is still using PORTA but the work is done behind the scene. You could just as well use PORTA = 0b0000010
  13. J

    Pull Up Resistor

    Look at it like this, You use a pull-up/dn resistor when you need to set the state to anything other then floating. What state that is will depend on its purpose.
  14. J

    battery interruption light

    Think voltage comparator. The zener voltage rating is the reference voltage when the battery is considered 'dead'. When the battery voltage reaches this reference voltage the output of the comparator will change. You can connect the output of the comparator to the LED indicator light. The big...
  15. J

    crimp on terminal help

    I don't know, but from where I come from we roll on down to the auto parts 'pick-a-part' junk yard and rip one out of a wreck. Then you just splice/solder the new one in place with a slightly longer overall wire length.
  16. J

    normally-closed, Push Button, where to buy it?

    You said the button would be outdoors, but that link you provided shows the button mounted inside. I highly doubt you need a very high quality momentary push button. Your current and voltage requirements are very low as well. I would look on digikey or mouser for a standard momentary push...
  17. J

    how to program this code from DS18S20@DS1820 to LM 35..please help me..thank :)

    This is asm code for a PIC16F628. DS1820 is a digital thermometer. What uC do you plan to port this code to? Each uC has slight differences and you will need to change the code to reflect this. It's not as easy as copy/paste upload to new uC. You also need the correct compiler this code was...
  18. J

    a doubt regarding saturation mode of BJT

    http://www.physicsforums.com/showthread.php?t=401308 You will probably get a better understanding if you learn form a physics perspective.
  19. J

    DC power jack

    You don't need a capacitor if you are using a battery because there is no ripple. With an SMPS, you will only need filter caps if the output ripple is more then your circuit can safely work under. As long as your two sources are very similar and you want to use a dc adapter, then you could...
  20. J

    Has anyone got this universal analog output circuit to work?

    It is not just a random vertical wire. It is the power to the IC containing the op-amps. It is a given to know that an op-amp needs power to work. edit: look at the schematic you posted a link to. It states "1/2 lm358". This is a double op-amp IC package, so they only show power connecting to...
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