Search results

Search Forums New Posts
  1. BobK

    DIY programmable battery charger

    What you are looking for is a buck converter. This allows you control the voltage supplied to the battery without simply wasting the extra power. When you are talking about 40A the wasted power would be huge and produce a lot of heat, so this is important. The buck converter is coupled with a...
  2. BobK

    What would be the effect If I change 4700uF capacitor to 18000uF?

    Need a circuit diagram. If this is a bipolar supply, which they usually are for high power amps, then the two capacitors are connected to ground in the middle, and you cannot replace them with one capacitor, if that is what you thinking of doing. Bob
  3. BobK

    Looking to get into Atmel programming, few questions...

    These are cheap. Only the first one seems to include a programmer, the other two links, which seem to be the same board, would need a separate programmer. Personally, I would spend the extra money and get a programmer and demo board directly from AVR. This way you know you will have support...
  4. BobK

    Capacitor Explosions

    Hmm. I blew up a 10uF myself by connecting it to 120V AC and an LED without a path for the current int the opposite direction, and it barely went pop. I would call it "venting" rather than exploding. Bob
  5. BobK

    Headphones from amp speaker wires

    With a 100Ω or more resistor in series, a short circuit would not be a threat to the amp. After Audio Guru's calclulation, I would start with a 220Ω 1W resistor instead of the 100 that I suggested. In all likleyhood, the amp is not really 45W RMS and you will have to reduce it to get the...
  6. BobK

    Ni-MH charging circuit query

    If the batteries are venting though, it is not because there is too much charge current, but that the current continues after the battery is fully charged. Measure the current after the battery has been on the charger for 4 hours or more. If that is more than about 50mA, there is a problem. Bob
  7. BobK

    Capacitor Explosions

    How big a capacitor? Bob
  8. BobK

    Why don't I get a Sine wave?

    You can get a sine wave by building a Wien Bridge Oscillator or a Phase Shift oscillator, or a Bubba Oscillator (love that name) Bob
  9. BobK

    Looking for a Microcontroller and RFID Module.

    Pretty much any micro will do. If you are a beginner, look at Arduino. Bob
  10. BobK

    How to get different OUTPUT voltages in ARM micro?

    You do not control a motor with varying voltage and a micro cannot output enough power to run a motor directly. Look up "PWM". Look up "motor driver". Bob
  11. BobK

    Capacitor Explosions

    I would not worry about using capacitors as a terrorist weapon. Watch some YouTube videos. They pop with less power than a 1/4 in firecracker. I'm not saying that they could not hurt someone, or you should not be careful, but this is not at the level of a real explosive. Bob
  12. BobK

    Headphones from amp speaker wires

    Happy Solstice to you too! Bob
  13. BobK

    Shorting a Battery

    So, you need about 5W to heat the socks. A 3.7V 760maH battery has 2.8WH or enough to heat the socks at best for a half an hour. I would be looking at a power bank with about 10000mAH which are commercially availabe for about $30 and have all the charging and protection built in. If the...
  14. BobK

    Headphones from amp speaker wires

    I would start with a 100Ω resistor in series with the phones. If it is still overdriving, try higher. Bob
  15. BobK

    carbon steel screw versus brass screws

    Hmmm. Looking at Lowes website, you can get a brand new outlet complete with 4 screws for 48 cents. Even at 8 cents per screw, salavaing seems pretty silly. Bob
  16. BobK

    Ni-MH charging circuit query

    The 4.7Ω resistor would limit the current. At 1A it would drop 4.7V bringing the voltage down to 3.0, which would not give you much charge current, so I think it probably limits the current to well below 1A which might be enough (AA sized NiMH cells should be able to take 1A charging current)...
  17. BobK

    Detecting Leveling of Arm and Shoulder

    If you want to know the limits of acceleration, look at baseball pitchers: http://resenv.media.mit.edu/pubs/papers/2006-06-IMU-Baseball.pdf Wow, 100 g's Bob
  18. BobK

    Ni-MH charging circuit query

    What is the source of the 7.7V going into the regulator? Perhaps the current is limited at the source. Is this a transformerless supply where the current might be limited by a capacitor? Bob
  19. BobK

    Help find this Mabuchi motor pinout

    The little circuit board should help you figure it out. The big black rectangular thing is the optical encoder. This looks like it might have 4 connections, which probably connect to 4 of the pins. The other 2 are probably the motor winding. Test the resistance of the assumed motor winding...
  20. BobK

    Ni-MH charging circuit query

    The powder is probably due to overcharging and venting. First of all, 3 NiMH cells is 3.6V not 4.8V. And it seems to be connected to a 5.6V constant voltage source (the zener + tratnsistor), which is horrible, the current needs to be controlled for proper charging. Bob
Top