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  1. redwire

    0-30V Stabilized Power Supply

    Then build it with the SOIC 8 package.  You will have a choice between  the TLE2141 or the MC34071.
  2. redwire

    0-30V Stabilized Power Supply

    Hi Twentysix, what design did you use and what values did you use for R13 and R14?  The reason I ask is because if you use the latest design that has a negative rail of -1.2 V instead of -5.6V and you use the original values for R13 and R14 then the voltage to the base of  Q1 may be positive...
  3. redwire

    0-30V Stabilized Power Supply

    Thanks  I wish I could read Czech to see the designers write-up from the original article.
  4. redwire

    0-30V Stabilized Power Supply

    Something similar was discussed several pages back.    IC1A seems to be missing the connections on pins 4 and 7.  It lists older  OpAmps  Tl082 which has a maximum voltage rating of 36 which is where it must operate.  I think the components used for the 9.5 V reference voltage is overkill, but...
  5. redwire

    0-30V Stabilized Power Supply

    A few weeks ago I changed the board by deleting U1 and associated components and replaced it with a 12V linear voltage regulator (PN  L78L12ACUTR).    I added two cap to keep the voltage regulator smooth.  Today the new PCB boards came in.    The only other board change was C7.  I switched to a...
  6. redwire

    0-30V Stabilized Power Supply

    Audioguru,  The power supply generates this kind of output at both startup and  shutdown.  Here is a shot of the startup with voltage set at approx. 0V.  The frequency is approx 24Mhz. As a side note if you end up leaving the load connected to the PS and start the unit or if you accidently...
  7. redwire

    0-30V Stabilized Power Supply

    I have a IC and LCD display attached and powered from a separate small transformer.  I tested it with the display on and off.  Perhaps I need to disconnect it then retest. Edit  I disconnected everything from the PS and still get the spike.
  8. redwire

    0-30V Stabilized Power Supply

    The first photo is when it is set at 12V and the transformer is unplugged.  The second photo is at when output is at max (approx. 30v)  and the transformer is unplugged.  It  looks like it is swinging approx. 30 volts negative then  30V positive resulting in approx. 64 Vpp. 
  9. redwire

    0-30V Stabilized Power Supply

    I was checking the output of the power supply when the power is quickly disconnected and discovered some large spikes.  I set the PS at about 12V hooked up the scope to the output with a trigger at 13V and got the following picture.  I did the same thing with the output at max with the same...
  10. redwire

    power supply

    what are you powering?  What are the output requirements?
  11. redwire

    0-30V Stabilized Power Supply

    Are you using a single turn or multi turn pot to adjust the voltage?  Is the slow descent only when there is no load?    C7 does need some time to discharge.
  12. redwire

    0-30V Stabilized Power Supply

    tcjeep,    I agree that a 1uF is a bit large, I  had the same concern.  I have a single turn pot and really didn't have issue with the responsiveness.    How often is there a need to instantly change the current control setting on pin 3?  Usually it is set ahead of time for a particular use. ...
  13. redwire

    0-30V Stabilized Power Supply

    I just received my Rigol 1074z scope.  I'm probing around the circuit and learning how to use this thing at the same time. Here is a screen shot of the output with the voltage set at zero- there is about 35mV output.  I am using a 10uF electrolytic cap, when I get a film cap i'll post the...
  14. redwire

    0-30V Stabilized Power Supply

    Wow!  I'm out of breath just reading this. The case of the 2n3055's is the collector which means if you have all 4 on the same heatsink and not insulated, then all will be live when either transformer is live.  Separate each side first. when you trouble shoot.
  15. redwire

    remote controled door 10 second delay

    why don't you  connect a resistor and led to the output (pin 3) of the 555 first. You can visually see what's going on.  Then work in the relay.
  16. redwire

    remote controled door 10 second delay

    Did you look up 555 monostable mode?
  17. redwire

    PIC18f2250 control over USB 2.0

    I have used Processing to build a nice GUI for the PC in order to send commands to an XBee connected to the computer, which send the command wirelessly to another Xbee connected to a microcontroller (Atmel).    The site is www.processing.org.   I know Arduino and Studio have hypertext window...
  18. redwire

    0-30V Stabilized Power Supply

    Understand.  I'm about to purchase a Rigol DS1074Z so I can have a 4 channel view.  I think it may take a couple of weeks to arrive.
  19. redwire

    0-30V Stabilized Power Supply

    Liquibyte, Although I quoted our discussion it was really a general statement for the board.  The project is advertised as 0-30V and many individual have discussed disappointment when they can not get to zero volts.    After reading over 140 pages of discussion,  you designed your board to...
  20. redwire

    0-30V Stabilized Power Supply

    While the current design works well and all parts work within safe operating conditions, I think the current design needs to be changed to connect  pin 4  of U2 to the negative rail (-1.3V), rather than ground to be able to adjust the voltage to a solid 0.  U2 would still be operating within...
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