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  1. Old Steve

    PT2272 Supplier - No data version - (3^12 address)

    Hi all, the title says it all. I'm looking for a supplier of PT2272 remote control decoder ICs in the 'no data' version, (12-bit tri-state address.) The M4, M6, L4 and L6 versions are easy to find, (6-bit/8-bit address), but not the 12-bit address version. Any help will be greatly appreciated...
  2. Old Steve

    74HC logic output signal

    Believe me, I'm still kicking myself for making such a silly mistake. The result was that the power to the circuit was cut off when the battery was fully charged, and connected when the battery went flat. :rolleyes: In my defense, like you it's been years since I last did any electronic design...
  3. Old Steve

    74HC logic output signal

    Yep. I'm with you on this. I (stupidly) got the pins of a comparator backwards the other day, and had to butcher the PCB to avoid re-making it correctly. (A one-off.) See pic below. Or even better, pins 1&2.
  4. Old Steve

    74HC logic output signal

    I don't think you have anything to worry about. Besides other considerations, on a breadboard it's hard to get the bypass caps close enough to the actual pins of the ICs. Just ensure that when you build the final circuit, the bypass caps are directly across the supply pins, even if that means...
  5. Old Steve

    Using an AAA battery to work a 220v clipper in N. America

    I was wondering myself if it was really 12V and not 1.2V, but figured it's possibly a moving coil type mechanism and not an electric motor. I'd personally buy a couple of normal carbon-zinc cells first to test it, before going to the trouble and expense of buying NiCd or NiMH cells to run it...
  6. Old Steve

    Using an AAA battery to work a 220v clipper in N. America

    Always fully charge the cells. You can pretty well ignore the slightly higher initial voltage after charging. It will almost immediately drop to 1.2V under load, when the clippers are turned on. If you were to only charge to 1.2V, the battery capacity would be very low and the clippers would run...
  7. Old Steve

    Using an AAA battery to work a 220v clipper in N. America

    You can't connect them in series or the voltage will be increased, they need to be connected in parallel as shown below. (I'd go with AA, too, rather than AAA, for the higher capacity.) Edit: I forgot to add - NiCd and NiMH aren't 'exactly' 1.2V. They start out a fraction higher straight after...
  8. Old Steve

    Using an AAA battery to work a 220v clipper in N. America

    I'd say 1.5V batteries should be fine, although the clippers would run a little faster. More than 1 cell in parallel would be best as previously mentioned, but if you want to get a closer voltage match and make it more economical you could use (rechargeable) NiCd or NiMH cells. Their output...
  9. Old Steve

    Li-ion under-voltage protection circuit

    Is that a 2K pot? That will also drain the batteries even when the load is switched off. You need to consider a much higher resistance pot, as suggested by Harald for the voltage divider.
  10. Old Steve

    Daylight-turn off

    I'd use an LDR connected to a comparator, with the comparator output switching the LEDs on/off. (LDR = light-dependent resistor)
  11. Old Steve

    NPN and relay cct

    Excellent, Jason. I'm glad it was a simple fix. I suspected that the diode might have been shorted, if it was in the right way around. (I sorted out my problem, too, so now we're both happy.)
  12. Old Steve

    LM393 Comparator Problem

    Back to the drawing board then, I guess. I might go back to a single 311 comparator, without the 4013, and see if I can get away with 1V of hysteresis. I'll also drop the pullup resistor value from 100K to 47K to speed up the MOSFET's switch-off time. If I can't get the performance that I...
  13. Old Steve

    NPN and relay cct

    It's got me stumped, Jason. As shown in the circuit, it should be impossible for R3 to ever get hot. Even if you connect R3 directly across the 12V supply, it should never get hot, let alone when across the base/emitter junction of a transistor, where the voltage won't ever exceed about 0.7V...
  14. Old Steve

    LM393 Comparator Problem

    Thanks for the reply, Harald. I didn't think I'd need to add hysteresis to the comparators in this particular circuit, (trying to reduce component-count), but I'll add a tiny bit to avoid oscillations when close to the switching point. The reason I went with 100K pull-up resistors on the...
  15. Old Steve

    NPN and relay cct

    Jason, are you sure you had the diode connected with the correct polarity? When connected as shown in your schematic, it should have no effect on circuit operation, and only conducts when the relay is turned off, to short any voltage spike that might be generated. (Or is the diode possibly...
  16. Old Steve

    LM393 Comparator Problem

    I'm hoping that someone can see what I've done wrong in this circuit, (attached). It looks fine to me, but I haven't done any electronic design for some years and must be getting rusty. It monitors a 9V Ni-Cd battery - the top comparator should go high when the battery voltage is 7.2V or higher...
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