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  1. J

    energy saving circuit

    Surely that is not everything you have on your mind? How is that supposed to help us help you? If you are worried about that clock on your vcr when the power should be out, don't sweat it. I could just send you the dollar it would cost in electricity over the next year. If I sound sarcastic...
  2. J

    DC/DC Power Supply Help

    Dave is correct, if you have 12V input and want out 14.5V at 80A, then your input will need to deliver more then 80A@100% efficiency. You can not create power out of nothing, you can only convert quantities of power. ex. want more voltage, then you will need to decrease your current. want more...
  3. J

    could you explain these topics in brief

    I really don't understand your question. Did you read the course outline, have you researched what an arduino and matlab are? They spelled it out in detail on the course syllabus what will be covered, what you manage to take away from the course will dictate what you do with the skill. If you...
  4. J

    Relay or similar between 5v dc - 240v ac.

    Well one way would be to use the 5V usb signal to drive a transistor that will be able to drive a bigger relay that can handle the 240V. There probably is a more elegant solution, recently others have talked about cords that will turn off printers etc. when the main computer is turned off...
  5. J

    Solder Rash?

    I should add, if you are that worried about it, go see a doctor. Your health is more important then anything. If you can't afford to see one then you have a choice to make. But, if your throat hasn't swollen shut yet, it most certainly won't by the time you read this.
  6. J

    Solder Rash?

    You have been unsoldering old boards? Depending on how old they might be the chemicals may be far worse then they are today. You should make sure that you are in an environment that promotes good air circulation. Try to keep your head off to the side, not directly over the board when you heat...
  7. J

    Electrolytic Capacitors

    if duke is right then you need a cap with good ripple rejection, I think that is what you want to ask the sales rep. I may be completely wrong though...
  8. J

    Need help for xmas project!

    Well that depends on how long you expect your led lights to work? Alfa is correct in that lithium batteries are by far the best battery, but they are expensive and are picky about heat. I also think they would cost more then this...
  9. J

    Need help for xmas project!

    You have to use resistors to control the current. Those LED's will drop 12 volts@wide range of current. If you do not use a series resistor the LED's will draw too much current and toast themselves. I think your series resistors are gonna need to be rather big as well, if they need to drop 6V...
  10. J

    help with project

    Well you will need a way to digitize your voice. That would require an ADC at the very least. Best you start by looking in that direction. Once digitized then it is up to your partner. Think mic > input sound card > software recognition > output w/e (which you will be on your own since you don't...
  11. J

    I want to learn

    The one thing I really like about the arduino is the flexibility it has. Using C is quite highly regarded as one of the best languages for hardware control. The linux kernel is coded in C as per an example. Also with the arduino, you can use their sketch IDE or you can code directly in C and...
  12. J

    Wireless doorbell to control remote circuit

    Have not read any of the first page, but yes, that is how a relay works. It either opens or closes a separate circuit. You hook 120V or w/e to the Normally open side of a relay and then activate the relay it will close the circuit and do whatever it is you want that circuit to do. The two...
  13. J

    Lighted wheelchair casters

    If resqueline is right, then the design is no different then a "permanent magnet alternator" with the output connected to some led's (think wind generators). You can google a PMA to see how it works as well as the LED's. Plenty of information out there with tons of examples to help you see how...
  14. J

    Portable heater thermostat

    How are you sure the sensor is bad? Doesn't make a whole lot of sense that the sensor is bad from the way you describe it. I admit though, I have never even looked at a PHR11 heater before.
  15. J

    I want to learn

    another very cool and pretty easy approach to micro-controllers are the arduino.
  16. J

    Run an mp3 player on a car battery?

    I think I would look at powered computer speakers. These should be good enough and they come prepackaged with an amplifier. You just need supply the DC power.
  17. J

    Run an mp3 player on a car battery?

    with bob's 1W example for 570 hours, you would need 46AH@100% efficiency. One car battery should handle that. But you will never get 100% efficiency out of a circuit. I think a typical car battery has a 70AH rating. I don't know how efficiency is calculated, but 70% of 70AH is 52AH. So it seems...
  18. J

    Run an mp3 player on a car battery?

    I could also see someone ripping off your batteries. They are not cheap and people will steal just about anything these days. Do you really want to spend that kind of money on something you have no control over? Looks like you have some decisions to make.
  19. J

    Run an mp3 player on a car battery?

    How big is the manufactures battery (yes there should a be an amp/hour rating for the battery?) How long does that battery last now when played continuously?
  20. J

    Broken toaster

    Well unless someone knows exactly how that circuit in your toaster works, we gonna need more information. Possibly a few pics of the components so we can get an idea on how it is supposed to work. Hell it might not even be electrical, there is a mechanic features in the toaster that could just...
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