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HT12D question — Parallax Forums

HT12D question

Steve2381Steve2381 Posts: 94
edited 2009-08-09 20:57 in BASIC Stamp
I have just added 3x HT12D receiver IC's to my stamp circuit. Anyone know how to stop the HT12D IC's starting up in 'latched on' mode? They clear once you send a valid transmission, but I cannot have them starting all latched on.
Thanks
Steve

Comments

  • FranklinFranklin Posts: 4,747
    edited 2009-08-07 21:10
    Have you checked the site where you bought them? If it's like parallax there will be data on the stuff they sell. Have you checked the datasheet and does it say this is even possible?

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    - Stephen
  • dev/nulldev/null Posts: 381
    edited 2009-08-07 22:06
    Have you tried to pull the VT pin low at startup?

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    Don't worry. Be happy
  • Steve2381Steve2381 Posts: 94
    edited 2009-08-08 08:21
    I will try pulling the VT pin low, although I am pretty sure I tried that. The data sheet does not mention it starting up in 'ON' latched mode, in fact, the data sheet actually lists the 4x output pins as starting low not high.
    I am simply driving a BC557 transistor on each output pin, so I don't believe they are contributing to the problem.

    As it is the remote control receiver, it plays havoc with everything when the system boots up, as you everything operates! You have to quickly send a transmission on each channel to reset the HT12D.

    Never simple is it!
    rolleyes.gif
  • dev/nulldev/null Posts: 381
    edited 2009-08-09 18:52
    I was just thinking... you could put a cap driven transistor (e.g. BC547) in front of your 557's to delay the current output until you've turned the latches off...

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    Don't worry. Be happy
  • Steve2381Steve2381 Posts: 94
    edited 2009-08-09 20:36
    I have delayed the outputs already. Its still not really an answer. You cannot use the system unless you quickly send a command with the remote control to reset the outputs.
    They should not be starting in latched on mode anyway. The data sheet says they start low. I have tried new IC's but they are the same, and with the loads disconnected.... no different.
    Its not the supply - checked that. Who knows!!!
  • dev/nulldev/null Posts: 381
    edited 2009-08-09 20:57
    I had similar problems with 595 shift registers. The latches would flicker like crazy at startup. I tried putting lots of caps on the power lines and it didn't help. What helped is when I grounded the chip directly to the voltage source. Don't ask me why, they should be the same, but that's what did it. I've also noticed that some components (for instance Color Cam from Parallax) behaved differently when I grounded it to the source.

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    Don't worry. Be happy
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