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  1. Arouse1973

    transistors for cap charge pump

    An FET might be better, they generally have lower on resistance. Adam
  2. Arouse1973

    voltage divider transistor biasing...

    The new suggested design should work ok but after a closer look there may be some issues you need to be aware of. 1) the lower frequency cut off has been shifted up to over 25K. Batt sounds range from 20Khz - 80Khz. The first modified design is around 12Khz.. The amplifier should be ok with...
  3. Arouse1973

    Solenoid Back EMF

    Hi Laplace. I was working out the correct protection diode for this circuit and had a look at the spike out of interest with the diode disconnected. I was after some accurate formula to be able to calculate what I saw, for a bit of fun. I don't know what else to add to the standard formula to...
  4. Arouse1973

    voltage divider transistor biasing...

    You will need a 3.7K I think for 9V.
  5. Arouse1973

    Frankenstein's Components.

    I want one! http://www.gabotronics.com/product-info/the-oscilloscope-watch.htm
  6. Arouse1973

    New Guy .

    I agree, welcome Electric. Adam
  7. Arouse1973

    voltage divider transistor biasing...

    If R1 is 75K, R2 is 18K, Rc 8K and Re 2K then you will have 4.5V on the collector. If this is what you want then you are correct. I chose Re for you because I couldn't see it anywhere. Base current is 1.17uA so as long as you keep the same transistor which has enough gain then it should work...
  8. Arouse1973

    Portable box

    Try RS components, farnell, Mouser, Digikey, Maplin. You shouldn't have much of a hard time finding parts here. Adam
  9. Arouse1973

    Stepper control using PC

    You might be better with I2C so each motor can have it's own address. You can get RS232 to I2C modules and then maybe something like this. This might get you started. I couldn't find a dedicated module though. http://www.nxp.com/documents/data_sheet/PCA9629.pdf Adam
  10. Arouse1973

    NFC Reader/Writer

    This might help Adam http://www.st.com/st-web-ui/static/active/en/resource/technical/document/data_brief/CD00184713.pdf
  11. Arouse1973

    Solenoid Back EMF

    Hi Guys What is the best formula for working out the back EMF of a solenoid. Now I have the results but wanted to calculate it for fun to see how close I can get to real life. This is a sealed unit so I can't see the coil. The coil is 24.6 Ohms and has an inductance of 20.6mH. The voltage...
  12. Arouse1973

    Inverter Circuit Help

    Coming into this a bit late guys but isn't this just loading of the reversed transformer on the output. If you go up in voltage you come down in current by your turns ratio. Ns/Np=Ip/Is Adam
  13. Arouse1973

    Touch dimmer slaves - how do they work?

    They might use the stage lighting standard D54 or have developed their own.
  14. Arouse1973

    Optics Help

    Ah yes we call this a separator, yes we have used this many times on other jobs. I can't separate the unit it's all build in one. But I will try what you have mentioned. Thanks Adam
  15. Arouse1973

    Optics Help

    Yeah valid point about the cone, hadn't thought of that. The cone is where you are guaranteed half power so this makes sense if the cone is narrow you have a larger irradiance at a point so 1% of that coming back is worse that 1% of say double the cone angle. How do you make the baffle. Thanks...
  16. Arouse1973

    Using a piezo as a vibration sensor

    Single layer Piezos produce a much higher voltage than current. So you will need to buffer the front end. If you load the output of the piezo too much you will reduce the response of the piezo. This circuit should be ok for the buffering but if you need to amplify the signal you will need an...
  17. Arouse1973

    Optics Help

    Didn't mean you were tall. Meant to say Hi :)
  18. Arouse1973

    Optics Help

    High John It's in the same package. the reflection is bouncing back of the surface. Yes agree with that but why is the optic glass reflecting this light when it should pass it. Also the shiny surface of the other side of the frosted plastic didn't reflect. thanks Adam
  19. Arouse1973

    Optics Help

    We did try this but it was not that controlled. It might be worth looking at this again as you have mentioned it.
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