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  1. redwire

    0-30V Stabilized Power Supply

    Liquibyte ,    Do you have any pictures of the back side with the fans.  I never thought about searching Ebay for heat sinks.    Did you ever resolve the issue with the low voltage output?
  2. redwire

    0-30V Stabilized Power Supply

    Liquibyte,  That is a beast! Looks well organized with no expense spared.    I have a couple of questions: What size transformer is in the middle (to power the display I assume?)?  Is the rectifier for that mounted on the bottom? What is the VA of the large transformers? It looks like you have...
  3. redwire

    0-30V Stabilized Power Supply

    liquibyte,  R7is the sense resistor, meaning if you measure the voltage drop across the resistor you can determine how much current is being drawn using I = V/R.  If you use a microcontroller to drive your display you can utilize one of the ADC pins to measure the voltage drop in order to...
  4. redwire

    0-30V Stabilized Power Supply

    Liquibyte,  I assume you are going to eventually have a  some sort of display.  You may want to determine if you need any connections from your board to the microcontroller for power. If you want to display the max setting of the current control, will you need  to measure the voltage of Pin 3 on...
  5. redwire

    0-30V Stabilized Power Supply

    Hi Zinci,  Welcome to the forum.  It's good to hear a new member's perspective of where we are.    I think there is one basic design that that been fairly consistant.  Audioguru reposts the sketch about every 2 pages because of the tremendous number of pages to weed through but that basic...
  6. redwire

    0-30V Stabilized Power Supply

    Liqidbyte Trace back from the bridge rectifier to pin 7 with your voltmeter to find where your voltage is dropping off.  You have a lot of solder on that board. Perhaps you have a short somewhere. If you are getting 10 V output it seems U2 (on the original project) is functioning properly...
  7. redwire

    0-30V Stabilized Power Supply

    Liquidbyte, On U1, Pin 7 is the supply voltage from the bridge rectifier, it should be around 41V.  You state that the U1 Supply is around 38V on the right side and 37.5 on the left.  I don't know how that is possible.  You list the voltages for every pin but 1 and 8. Those pins are not...
  8. redwire

    0-30V Stabilized Power Supply

    Liquidbyte,  can you post the values of all of the pins for U1 They should be close to: Pin 2  5.6v pin 3  5.6v pin4  0V Pin 6  11.2V Pin 7 41 V Also check the resistance value of R5 and R6  to see if they are both 10K.
  9. redwire

    0-30V Stabilized Power Supply

    liquidbyte,  what is  the voltage at pin 6 on U1 and what is the voltage of pin 3 and pin 6 on U2 when you are at max voltage?
  10. redwire

    0-30V Stabilized Power Supply

    liquibyte  are you going to surprise us with something like this http://www.4dsystems.com.au/downloads/microLCD/uLCD-43/Docs/uLCD-43-Product-Brief-REV1.2.pdf
  11. redwire

    0-30V Stabilized Power Supply

    liquidbyte ,  I  I personally think you are splitting hairs on getting to exactly 44V or less  on U2, but if it helps you sleep better, you could  put a 5.6V zener between the positive rail and pin 7 of U2.  Since you need at least one 5.6V zener for the project, it is likely you have a spare. ...
  12. redwire

    0-30V Stabilized Power Supply

    You are correct.  I  must have been thinking of another circuit.     On another note, there is no reason for U1 to need a 41V input rail.  It only needs about 13-14V in order to supply a constant 12.2 V.  Why didn't we connect the positive rail of U1  to the 10V zener like U3 and drop 10V?
  13. redwire

    0-30V Stabilized Power Supply

    liquidbyte   I have the Triad Magnetics VPS28-6250 (175VA) transformer and I am getting approx 41VDC rectified.   Add another 2V for the negative rail on U2 results  in 43V across U2.   The TLE2141's are rugged devices.    In my first unit, I used a home built transformer that puts out nearly...
  14. redwire

    0-30V Stabilized Power Supply

    What is the value of R7?  if it is 0.47 Ohms,  you need to use  0.27 Ohms.  Did you adjust the 100k pot to allow a higher current?
  15. redwire

    0-30V Stabilized Power Supply

    U1 and U3 need to provide very little output current.  U2 is the real driver in this circuit.  If electroguy utilized a darlington power transistor instead of the 2N3055 then the BD 139, and subsequently the MC3074 would need very little current to drive the BD139.  I think the quad opamp could...
  16. redwire

    Calculation of voltage using Kirchoffs laws

    In your diagram you assumed the current flowed clockwise and then showed + and - convention over the resistors indicating a voltage drop across them.  Your equation becomes 5v -I*R1 - I*R2 =0;  With   R1=R2 ; I = 0.025A.   Going back to the original diagram working from the voltage source to...
  17. redwire

    Pic16F628a connection

    both look like they operate at 5V.
  18. redwire

    Stepper Motor Speed Control

    Try increasing the current by applying more voltage.
  19. redwire

    Single Chip Temperature Data Logger

    I don't think we have connected on the issue of programming the chip.  When you asked the question   It concerns me that you don't recognize that it takes a programming board to move the program from the computer to your board.  The pins that you have identified in question 4 are used as a...
  20. redwire

    PLEASE HELP ME

      How far do you need to transfer the signal?    Have you looked into  XBee modules?  This guy has a 5 part series on features and setup.  The video starts out kind of weird but the content is excellent. 
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