Editing Wireless remote switch, button press: 1 second=ON, 3 seconds=OFF
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− | ALL MY PROJECTS ARE HERE: | + | ALL MY PROJECTS ARE HERE: http://www.opencircuits.com/User:Definitionofis |
I bought a 315Mhz transmitter/receiver pair of postage stamp size inexpensive boards from robotshop.com. Ebay has them too. | I bought a 315Mhz transmitter/receiver pair of postage stamp size inexpensive boards from robotshop.com. Ebay has them too. | ||
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lightning and that is not acceptable, thus my filter idea using 60Hz pulses modulating the 315Mhz carrier. | lightning and that is not acceptable, thus my filter idea using 60Hz pulses modulating the 315Mhz carrier. | ||
− | Lightning is not 60Hz and other devices, which I monitor in my neighbourhood, are typically 1000Hz through 4800Hz data pulses | + | Lightning is not 60Hz and other devices, which I monitor in my neighbourhood, are typically 1000Hz through 4800Hz data pulses. |
[[File: LTspice_60Hz_for_1second_goes_through_to_Q2_as_0.7vdc.png]] | [[File: LTspice_60Hz_for_1second_goes_through_to_Q2_as_0.7vdc.png]] | ||
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[[File: LTspice_60Hz_pulses_to_transmitter_data-input.png]] | [[File: LTspice_60Hz_pulses_to_transmitter_data-input.png]] | ||
− | Other notes | + | Other notes: |
+ | I tried to omit the 3H inductor (all references are to the top schematic part numbers, not the LTspice diagrams) and I ran into a small problem with the data being vdc. The inductor converts it to AC. I think a large serial capacitor would work instead of an inductor, but then maybe it cannot be a polarised type of capacitor; ie. too expensive. On the other hand, a smaller serial ceramic capacitor would work with a mosfet gate, instead of a transistor base (smaller current). I stopped thinking about it since I have an old small power adapter transformer to use as 3H inductor and it works. (Edit: I solved those problems. See the new schematic. It can be a 4.7uf polarized capacitor. I removed the inductor and the frequency response still cuts off > 200Hz completely. You can transmit and receive at other frequencies and modify that filter. I chose 60Hz because it is easy to convert 60Hz house power into low voltage transmitter data input. A 555 timer IC could do any other frequency.) | ||
− | + | Circuit function: | |
+ | That circuit idea is very complex. I got a version of a button-press-latch circuit with a HOLD-for-OFF feature, from somewhere and it did not work, although they claimed it worked. I added 5 parts to make it work. Without LTspice I never would have deciphered the error. HOLD-for-OFF makes it very complex. EEVblob had one simpler, without the HOLD-for-OFF. | ||
− | + | Q1 could be just an ON-button-switch. C2 is the trigger for pumping Q2 base ON. Q3 pulls Q2 base high (OFF) during the delay hold of 6 seconds. That seems simple enough. But the D3 and D5 diodes are essential to omit the reverse signals which we want to discard. Then D3 causes a problem because it has a forward voltage and is not really ground. A schottky diode has a lower forward voltage and might be low enough to pull Q3 base near enough to ground. I added D7 to raise the emitter instead. Then the diodes are all the same. I also added R8 to help benefit Q2 base. R8 cannot be too large or it slows another part of the cycle where we want Q2 base pulled high! A conflict of objectives occurs, thus 10k worked and maybe 50k would not work. R8 raises the emitter a little more, which is also essential at micro-amp currents when diodes do not obey what you think are the forward voltage specifications (haha); ie. forward voltage is lower than you think. | |
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Next, the Q2 was originally a p-mosfet and the circuit failed completely without R10 while using a mosfet because the mosfet does not self-discharge the gate during part of the cycle, like does a pnp transistor (a mosfet gate is a capacitor!), and D5 also blocks the discharge negative to positive. In other words, base-emitter is much lower resistance than a mosfet gate, which is near infinite resistance. So R10 is maybe not necessary if Q2 is a pnp. I left R10 in anyway in case I change it to a high current p-mosfet some day so the mosfet gate gets discharged through R10 during part of the cycle. | Next, the Q2 was originally a p-mosfet and the circuit failed completely without R10 while using a mosfet because the mosfet does not self-discharge the gate during part of the cycle, like does a pnp transistor (a mosfet gate is a capacitor!), and D5 also blocks the discharge negative to positive. In other words, base-emitter is much lower resistance than a mosfet gate, which is near infinite resistance. So R10 is maybe not necessary if Q2 is a pnp. I left R10 in anyway in case I change it to a high current p-mosfet some day so the mosfet gate gets discharged through R10 during part of the cycle. |