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fireball
Joined: 05 Apr 2004
Posts: 3
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| Remote control |
 Posted: Mon Apr 05, 2004 8:41 pm |
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Hi people, can any body help me with designing a remote control?
My idea is to use a TX/RX pair (http://www.computronics.com.au/module/txrxpair/) with a PIC621 sending a series of pulses on a delay or timer interrupt (a code) to the txmitter module for multiple chanels. How would i code the reciever end to interpret this signal after waking up from sleep mode when it recieves a signal? say i have a 1kHz 32-bit digital signal with a series of highs and lows for one channel and another series for a diffrent chanel. The reciever outputs (to the MCU) the digital signal trnsmitted by the trxmitter. The decoder to be programmed will be a PIC16F877 that will drive a motor with a 500Hz pwm pin and a current sensor through the motor on an A2D converter pin. What's the best way to arrange the timer interrupts to accomodate for both of these? And which pins will these be best for?
This other question is a hardware issue. I have a standard car alarm remote control "case". It holds a very small round 12V batery only. If I use a 7805 voltage regulator and the micro controller in sleep mode with wake up on pinchange..... will the 7805 be sucking the juice out of the batery? Or will i have to tape a series of button 1.5v cells to get 4.5 or 6v to avoid using a voltage regulator?
My question, here is, how much current will a 7805 voltage regulator use when only 1microamp is being drawn from it. I can't work this out from the datasheets.
If this post recives a reply and you have a better idea, other than the one mentioned by me or the ones that have been posted by others please post a reply. Thank you. |
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Neutone
Joined: 08 Sep 2003
Posts: 839
Location: Houston
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| Posted: Mon Apr 05, 2004 9:25 pm |
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| Explain the application. |
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Guest
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| Re: Remote controll |
| Posted: Mon Apr 05, 2004 10:20 pm |
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| fireball wrote: |
My question, here is, how much current will a 7805 voltage regulator use when only 1microamp is being drawn from it. I can't work this out from the datasheets.
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Way too much. The quiescent current, Iq is what you'll see with no load. I usually run my projects on 3V or 4.5V if needed. If that's not practical, you can find low-Iq regulators or build a buck switchmode regulator, though I think some (all?) of those need a little load on them to stay stable. Keep looking, the garden variety 7805 is horribly inefficient and is not your friend in battery powered applications. |
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fireball
Joined: 05 Apr 2004
Posts: 3
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| aplication |
| Posted: Mon Apr 05, 2004 11:26 pm |
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the application is a 4 chanel remote control gate and door opener and closer.
i'm starting with the gate reciever if u can help me with that.
Thanx for the tip on the 7805.
Will the PIC12F621 run off 6 volts? (limit 5.5V)
and what will happen if i put a resister at Vdd (6v) when one pin is drawing 9mA (transmitter here is powered by this I/O pin), another is Drawing 5mA(an LED)when i press the button, another pin is suplying code(almost no current).
The MCU is running with an internal oscilator, will the oscilation vary when i change the load? (I/O pins turning on and off suplying periferals). Will i still get the same code outputting one pin if Vdd fluctuates a small amount because of the voltage drop across the resistor placed between 6v batery and chip suplying power to all periferals?? |
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Ttelmah
Guest
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| Re: Remote controll |
| Posted: Tue Apr 06, 2004 2:28 am |
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| fireball wrote: | Hi people, can any body help me with designing a remote control?
My idea is to use a TX/RX pair (http://www.computronics.com.au/module/txrxpair/) with a PIC621 sending a series of pulses on a delay or timer interrupt (a code) to the txmitter module for multiple chanels. How would i code the reciever end to interpret this signal after waking up from sleep mode when it recieves a signal? say i have a 1kHz 32-bit digital signal with a series of highs and lows for one channel and another series for a diffrent chanel. The reciever outputs (to the MCU) the digital signal trnsmitted by the trxmitter. The decoder to be programmed will be a PIC16F877 that will drive a motor with a 500Hz pwm pin and a current sensor through the motor on an A2D converter pin. What's the best way to arrange the timer interrupts to accomodate for both of these? And which pins will these be best for?
This other question is a hardware issue. I have a standard car alarm remote control "case". It holds a very small round 12V batery only. If I use a 7805 voltage regulator and the micro controller in sleep mode with wake up on pinchange..... will the 7805 be sucking the juice out of the batery? Or will i have to tape a series of button 1.5v cells to get 4.5 or 6v to avoid using a voltage regulator?
My question, here is, how much current will a 7805 voltage regulator use when only 1microamp is being drawn from it. I can't work this out from the datasheets.
If this post recives a reply and you have a better idea, other than the one mentioned by me or the ones that have been posted by others please post a reply. Thank you. |
For this sort of application, look at the Motorola 78LC50. Be careful to have good capacitor layout close to the regulator (they are more prone to oscillation than the normal 7805), but have a quiescent current of 1.3uA.
They work well in this sort of system.
Best Wishes |
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