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  1. BobK

    RS232 & Crossing RX/TX Lines

    Of course you could always put in pin strip headers and use jumpers to make the connections, just in case. :)
  2. BobK

    making a big magnetic field

    I suspect the robots are limited in size and weight. Otherwise someone would just use a monster truck. Bob
  3. BobK

    making a big magnetic field

    I believe there is a rule on this forum about helping with weapons. Bob
  4. BobK

    RS232 & Crossing RX/TX Lines

    Connect the T1IN and R1OUT to the TTL device TX and RX Connect the T1OUT and R1IN to the RS232 device RX and TX Bob
  5. BobK

    How to connect a stepper motor to a bipolar driver

    Two of the 6 wires will be center taps of 2 others. I.e. there are actually two center-tapped coils. Use an Ohmmeter to determine which wires are which, and then just ignore the center tap wires. Bob
  6. BobK

    2 pole low frequency shelving filter design

    How is the -0.5V applied? Are you using that instead of ground? That makes no sense. Bob
  7. BobK

    Lab power supply from microwave transformer project.

    Say hello to Phryne Fisher for me! Or would that be G'day? Bob
  8. BobK

    Using ohms law to calculate how many devices can be used with power supply

    You could measure the Vf by simply putting a voltmeter across the LED when it is operating. It is normally around 2.5V for red and 3.6V for green and blue. But I suspect your 40W LEDs are actually 3 LEDs in series, so they would be more like 7.5V and 10.8 for the others. Then the current...
  9. BobK

    HDMI to LVDS converter

    That appears to go the right direction. But this is not going to be an easy project. How much is your time worth? You are going to work how many hours to save, at best, $25? What hourly rate does that come to? Bob
  10. BobK

    Arduino Theremin Frequency help

    I did not read the description in the link, so perhaps I am wrong about this, but here is what it sounds like to me: I think the Arduino is mapping the output of the sensor to one of the standard 12 notes so that it changes the frequency only in discrete steps. Normally, a theremin would...
  11. BobK

    Using ohms law to calculate how many devices can be used with power supply

    If you are using a constant current of 600mA for each of the 4 LEDs you are probably not using the entire 40W capability of the LED. What is the forward voltage of the 4 LEDs at 600mA? That will tell you how much power you are actually drawing. It will also tell you how many you can put in...
  12. BobK

    2 pole low frequency shelving filter design

    You already have it biased at 2.5V. This would allow it to go only 0.5V to the + and 2.5 to the minus. You could redo it to bias to 1.5V in order to get the maximum symmetric swing. To make it 1.5V the two resistors should be chosen such that it is a voltage divider in the ratio of 1.5/5 and...
  13. BobK

    HDMI to LVDS converter

    With a PCB, cables and connectors, I don't see how you could come in less than $35. Also, the chip you linked goes the opposite way, from LVDS to HDMI. Bob
  14. BobK

    Parallel connection of BJTs ,constant DC supply

    I wonder if he is trying yet another free energy scheme? Bob
  15. BobK

    2 pole low frequency shelving filter design

    5V is too low for use with an LM324. Its output can only swing to within 2V of V+, so your output could only swing from 0 to 3V which is not enough for line level audio, presuming that is what you are aiming for. I would use 12V, or at least 9. Bob
  16. BobK

    Need Help in SCR/TRIAC Project

    Here is a link: http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FODM3012R2V_NF098/?qs=sGAEpiMZZMteimceiIVCB6I5k3wqkA2zIyaVFd2K9yc= The biggest one Mouser has can handle 2A, so probably not good enough for the OP. Edit: I used one like this to pulse a laminator motor for toner...
  17. BobK

    2 pole low frequency shelving filter design

    Well, you didn't copy well then. The circuit you posted has 2 stages, both containing capacitors in the feedback network. These will be filters. The circuit you posted is just an amplifier. Now, in response to your original question. Make the resistors that connect to ground, two resistors...
  18. BobK

    Hold 5v Line

    Sounds to me like you have connected the output back to the input of the first Schmitt trigger, making it an oscillator. The time constant is even correct, 330K x 33uF is about 10 seconds. Bob
  19. BobK

    Picking and understanding microcontroller for a project

    128x64 is 1024 bytes, but that would represent only single bit per pixel. I expect that it is actually either 4 or 8 bits of grayscale per pixel. That makes it either 8192 bytes or 16384 bytes per image. Typical microcontrollers do no have much memory. 128K of flash and maybe 32K of RAM for...
  20. BobK

    Need Help in SCR/TRIAC Project

    There are also triacs with built in optocouplers. And some Solid state relays are basically that. Bob
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