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Hero999

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Posts posted by Hero999

  1. It's not too critical, as long as the op-amp can tolerate 44V but unfortunately not many modern op-amps can.

    You could use the OP27 but you'll need to modify it because the offset trim configuration is different.
    http://www.analog.com/media/en/technical-documentation/data-sheets/OP27.pdf

    Another possibility is the NE5534 but it requires a compensation capacitor and has higher bias currents.
    http://www.onsemi.com/pub_link/Collateral/NE5534-D.PDF4

  2. There have been no posts now for over a week, apart from this thread. The forum has died, since the upgrade.

    The new software may be more secure but it's no good if half of the old forum content is gone, along with the members.

    The new software, also seems to be less easy to use and lacks features or they're hidden. Where is the quote button? How about the smilies and fonts? What about the preview button to check ones reply, before submitting it?

  3. Yes K, A G does normally mean SCR.

    But the socket seems to indicate it uses the whole waveform and there are only two diodes, rather than the four expected in a full wave rectifier.

    You really should try to draw the schematic, even if you're not sure of the components. Just draw the TRIAC/SCR as a box with the pins numbered from left to right (front view).

    Another thing you could do is consider stripping out the original circuit and replacing it entirely with a standard phase controller circuit.

  4. It can't work as a lamp dimmer because it's zero crossing. For a lamp dimmer you need a TRIAC which can be triggered in the middle of a cycle. This solid state relay can only be triggered at the start of the AC cycle when the voltage across the TRIAC is near zero. It will then remain on until the current falls to zero.

    It could be used to control a heater or turn a motor or lamp on and off.

  5. It's a solid state relay with a DC input and TRIAC output.

    A solid state relay does not convert the voltage. It enables a low current signal to switch a higher current on and off.

    This type of relay has a TRIAC output. It will only turn off when the current flowing through the output falls to near zero and it has zero crossing so it will only turn on when the voltage across the TRIAC on the output is near zero. It is only suitable for switching AC.
    http://www.farnell.com/datasheets/1672165.pdf

    Here's a simplified schematic of what's inside an AC solid state relay:


  6. I have been looking around (ebay, google, etc) for a basic digital thermometer preferably diy and everything I've found has an accuracy of only 0.1 C or less
    How hard would it be to build a basic one with an accuracy of 0.01 or 0.001 C?

    Don't confuse resolution with accuracy. They are different things.

    Of course it's possible to make a thermometer with a resolution of 0.001oC but it won't be necessarily be any more accurate than a cheap one with a resolution of 1oC

    Over what temperature range?

    Getting a high accuracy over a large temperature range isn't easy and it certainly won't come cheap.

  7. I doubt the circuit is capable of driving a relay.

    You can probably connect the base to the output of the circuit which drives the LED. It will already have a current limiting resistor for the LED which should also be fine for a transistor.

    The ZTX690 is widely available. Digikey and Rapid Electronics stock them.
    http://www.digikey.com/product-search/en?vendor=0&keywords=ZTX690B
    http://www.rapidonline.com/Electronic-Components/Ztx690b-Tran-Npn-45v-2a-Eline-81-0230

  8. That's odd. The ON semiconductor datasheet lists a maximum IC of 800mA but Hfe is only specified at 300mA, Hfe > 60 VCE = 1V.
    http://www.onsemi.com/pub_link/Collateral/BC337-D.PDF

    600mA with a forced beta of 30 doesn't seem unreasonable but a heatsink would be a good idea. Don't forget the minimum beta is normally specified across the temperature range (-55C to 100C) so at room temperature or warmer, it'll be much higher than the minimum.

    Failing that, use an higher beta transistor:
    http://pdf.datasheetcatalog.com/datasheet/sanyo/ds_pdf_e/2SC3807.pdf
    http://www.classiccmp.org/rtellason/transdata/2sc3616.pdf
    http://www.diodes.com/datasheets/ZTX690B.pdf




  9. I believe that board is dropping the voltage down before the LEDs on the board reason being, if I check the voltage between the positive of the LEDs and ground on the board it is 2v. So from that I assume that board is already dropping the voltage before it gets to the LEDs.

    The 12v LEDs are meant to be hooked up to the bike battery, as thats why they are 12v with a 60ma per strip. These are just the specs from the manufactures, but I don't have them with me currently to test.
    It's more likely that each LED has a series resistor to limit the current and the LED foward voltage is 2V.

    If you remove an LED, you'll probably find the voltage increases to 3V.


    The new load will be 600mA. An ordinary transistor saturates fairly well when its base current is 60mA which is too much for an LED unless it is a big very bright one. So the receiver output must be analysed to see if it can be modified to supply 60mA.

    The BC337 might do. It's specified with a minimum Hfe of 40 when IC = 500mA and VCE = 1V
    http://pdf.datasheetcatalog.com/datasheet/philips/BC337_3.pdf
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