Search results

  1. MP1

    sensitive low frequency filter

    I probably should not have gone on so long winded with that last post. Let's continue the filter design theory in the theory section if you want to continue the discussion there. Lets keep this thread going for the low pass filter Rich needs to get going, ok? MP
  2. MP1

    sensitive low frequency filter

    If I am not mistaken, the term 2 pole or twin T refers to two networks that look like a T built from capacitors and resistors where the bottom of the T is connected to ground. If the two components that make the top of the T are resistors, then you have a low pass filter whereas if the two...
  3. MP1

    HO Scale Slot Car Racing Tree

    If you can post it here, I am sure you will get many comments and suggestions. When you attach the graphic such as a jpg, it will display it in your post. MP
  4. MP1

    sensitive low frequency filter

    It is a third order lowpass filter. The gain is fixed so I am not surprised that Rich is having a problem with the gain. Although you can add gain to the output, if he is using a passive input such as a microphone, then he is going to need some amplification at the input. Microphones give out a...
  5. MP1

    looking for data on LINE IN of soundcards

    Here is a site with the same interest: http://www.interstice.com/drewes/answer/ MP
  6. MP1

    High Quality electronic sites

    Here I will add a few: http://www.geocities.com/puo_mcchin/Download.html http://www.commlinx.com.au/schematics.htm http://www.datasheetarchive.com/ http://www.designnotes.com/Circuits.htm http://www.keelynet.com/sources/schema1.htm http://www.glolab.com/freeinfo/info.html...
  7. MP1

    Cell phone dial indicator

    Here is a comparison of the data sheet specs. These diodes have some differences. Have you checked to make sure all of you components are oriented correctly? I have not built this project, so I do not know the specs on it. I suggest that you check the parameters of the data sheet with the...
  8. MP1

    State Variable active filter

    Hi Rogy, welcome to the group! Fc is the frequency of cut off for high and low pass, but it is the center frequency when you are using the band pass output. The following formula applies to this filter: Fc - 1 / (6.28 * R * C) where Fc is the centeror cut off freq., R is R2 through R9 in ohms...
  9. MP1

    Help in simple project design

    desmond, it seems that you are certainly going to need to get the data sheet of the chip to see what is in there. Most data sheets will give some kind of an internal diagram. Once you have this, you will be able to find a solution. As you have stated, there are resistances and shorts internal to...
  10. MP1

    Help in simple project design

    What is supposed to happen when you close the switch? All LEDs light? What actually happens? Does this sit on top of the chip in your second diagram or does it plug into the board where the chip would normally be? MP
  11. MP1

    4N25 Schematic check

    It is always a good idea to use an optoisolator when connecting a device capable of EMF to a computer. But sec brings up a good point. Is the 5V source coming from other switching circuitry or is this just part of the power supply? At the very least, you should include some power diodes across...
  12. MP1

    Help in simple project design

    So do I understand that you have 26 connections to poll at the same time and you are looking for one of the connections to be shorted? It would help to see the circuit, but here are some ideas: 26 of the same circuit in parallel Add some rotary switches Use 4066 cmos switches Do you have a way...
  13. MP1

    4N25 Schematic check

    One other thing I thought about that was not mentioned in your post: Have you checked the data sheet for the 4N25 to see if it is capable of the current required by the fans? MP
  14. MP1

    4N25 Schematic check

    Backwards. You would normally connect power to the collector. These are NPN transistors. Are you aware the fans have two different voltages? Are they different fans? MP
  15. MP1

    Help in simple project design

    Because of the high impedance of the circuit, you might consider making a LED probe which only comes on when the circuit is shorted. The shorted contacts would complete the circuit. MP
  16. MP1

    Make the cdw,mp3 to work off speakers

    This area is fine for this question. However, it might have gotten more exposure in the circuit requests area. It is really hard to answer this question without at least a block diagram of how your system is put together. There are so many different types out there that a generic answer would...
  17. MP1

    SAD 1024

    Not directly replacable by the MN1024, but you could use it instead if you lay out a different circuit board. It uses a different pin out and clock ckt. The SAD1024 was very prone to circuit noise whereas the MN1024 was not. In fact, the SAD chip was so bad with noise that you would almost...
  18. MP1

    SAD 1024

    The SAD 1024 is a "Bucket Brigade" analog delay chip made by Reticon, discontinued several years ago. It is obsolete and you will not find one except in some rare surplus lots. If you happen to have one, you will find that they were used primarily for flangers, chorus, and echo music effects. I...
  19. MP1

    OPAMP questions

    You might want to start here: http://pasture.ecn.purdue.edu/~abe591s/Opamp.pdf MP
  20. MP1

    handy tip for intefacing your PC with projects

    Here is the Parallel Port. ;) MP
Top