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  1. MP1

    Epson bi-polar step motors em-236 & em-237

    It is probably more dependent upon who IBM purchased them from. I do not think they make their own. How many wires do you have and what are their colors? This will be more helpful. Also, I usually measure the resistance from wire to wire to map out the windings. You will find the coil resistance...
  2. MP1

    Capacitor variety

    I was thinking about this in an audio type of set up. Car stereos need a large bypass capacitor on the 12 VDC power side to help deliver the good base response from the newer high power amplifiers. Usually a 1 farad capacitor is used. However, such large value capacitors are very expensive. If...
  3. MP1

    4N25 Schematic check

    audioguru, good eyes! Yes. The relays will not work if they are 12 VDC coils and only have 5 VDC to activate them MP
  4. MP1

    State Variable active filter

    Tone control takes a very stable circuit. A circuit which just barely passes would not be workable in the audio field. It certainly would not allow you the ability to change a resistor or capacitor value and cover a wider range of frequencies. Output bias is not needed. You need more study of...
  5. MP1

    4N25 Schematic check

    Yes, just like the example in my last post. That is what the diode is there for. This is also a relay driver. By the way, how much current does the relay require to turn on the coil? Do I recall that the switch is not really a switch? That it is another device? You should check to be sure you...
  6. MP1

    HO Scale Slot Car Racing Tree

    I saw your posted schematic but did not understand what you were trying to accomplish, so had hoped someone more familiar with your hobby would converse with you. ( I am not an HO enthusiast.) I do not see a way to trip the circuit. It is only connected to a 555 timer and thus will always run...
  7. MP1

    ISA Bus oscilloscope Project

    How is the A/D reading the input? I mean is it placing the signal on the parallel port, serial port or where? Or did you assign it an IRQ? I am not sure that even with this information I will be able to help, but I think this information will be needed in order to get you the help you need. The...
  8. MP1

    Power Supply For tattoo Machine

    In other terms, some reason is causing the load to be grounded through the rheostat. This could be the polarity of the plug, a mis-wired terminal or something else. It is not possible to go further without seeing the schematic or wirng diagram. Since you have two and one is working, you can...
  9. MP1

    4N25 Schematic check

    Here is a control circuit (switch) that can be used with most any small PNP transistor such as 2N3906. When the resistor to the base is connected to ground (or close) the transistor is in an "ON" state. The diagram shows the switch used to turn on a relay but it could be used the same for a...
  10. MP1

    Simple circuit switch

    I am not sure I followed the concept, so excuse me if I am way off the track here...but wouldn't a CD4066 CMOS switch IC do the job without the additional circuitry? MP
  11. MP1

    Pc controled fluid selector

    You can control the motor directly from the PC. A stepper would be easy but you would need some type of feed back circuit to tell you where you really are. This could be opto switches, etc. The other choice would be a servo motor with the internal feed back which always knows the position. The...
  12. MP1

    Flasher?

    This can be done with 555 timer chips. There is a link to a tutorial with examples in another area of this site. There is also a large project area which might have what you need. Have you browsed the site? MP
  13. MP1

    0-30 Vdc Stabilized Power Supply

    The boost with transistor(s) is how I do it, also. Although I use a NPN instead. Either method can be used. The reason I jumped in was your statement "CANNOT". And as you see, it CAN be done. You are correct that you will have some loss due to the resistors, but overall, you will have a boost...
  14. MP1

    0-30 Vdc Stabilized Power Supply

    Thanks, the post ended up out of place and it was not clear to whom you were answering. I agree that it is not good practice to parallel the power supplies, but you should know that it is general practice to parallel regulators such as the 78XX or 79XX series to get more current rating from...
  15. MP1

    Power Supply For tattoo Machine

    The power supply is capable of 3 amps. I could not access the link to the rheostat, but Radio Shack does not carry a rheostat capable of more than 500 ma if I recall correctly. As you decrease the resistance to ground in your circuit, you are asking the resistor (rheostat in your case) to carry...
  16. MP1

    Car stereo amplifier output ratings

    You have to be careful on this type of generic voltage calculation as some high powered amps are using DC to DC converters and are actually running on 35 to 45 VDC. This changes the calculation considerably. Although it still runs from a car battery at 14 VDC, the amp is running on 35 or 45 VDC. MP
  17. MP1

    Help in simple project design

    Nettron, I refer you to the data sheet of a 4066 cmos switch. Internally, pins are commonly shorted together by some type of reaction to the other pins. For example, without the data sheet on this chip, one might connect a test circuit which adds voltage to the control pin and causes two other...
  18. MP1

    Capacitor variety

    siddhu, this is interesting. What physical size was your capacitor and what Farad rating did it turn out? MP
  19. MP1

    0-30 Vdc Stabilized Power Supply

    audioguru, what are you referring to in this post? Multiple regulators in parallel? Complete supplies in parallel? Which post are you replying to? MP
  20. MP1

    Help in simple project design

    He said shorted together. After looking at the diagram he has posted it should be clear that he is using the term "short" to mean connected together. What is not clear is what is connected to what in the IC. When you have a schematic with an IC that performs as some type of switching mechanism...
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