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Old Mar 14, 2005, 04:45 AM
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Smolensk, Russian Federation
Joined Aug 2004
14 Posts
Power Switch with Voltage indicator

It is relatively simple power switch with 4-LEDs battery voltage indicatior. Used MOSFET can easy handle about 4 Amp without overheating, it is enougt for most common aplications (If you can glue small cooler to mosfet it can teorethicaly handle up to 18A)
U1 - 3.0 volt linear regulator
R6 - you may want to decrease down to 56 Ohms - LEDs be brighter.
Afrer power of at first time you will preset four voltage levels for 5-cells battery and next four fot 4-cells. For enter to preset mode push and hold button then apply power.
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Old Mar 14, 2005, 05:26 AM
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Manila, Philippines
Joined Jul 2004
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Romych: Thanks for sharing your circuit....whats the current drain of your circuit when its off, I guess its the same current Drain of PIC when its in sleep mode.....I like your idea, cause I have encounter some electrical failure using those Mechanical Switches.

have you tested it your helicopter/plane, I just worried if something happended to your pic controller if its HANG-UP...it might accidentally turn-off the MOSFET.
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Old Mar 14, 2005, 06:13 AM
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Smolensk, Russian Federation
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During "power-off" it is draw about 300uA - it is mainly "stand-by" current of voltage regulator. On next board I plane to use MC78LC30NTR (Quiescent current no more 3,3 uA). PIC sleep current relatively small... I am use this switch (on my fun-fly glow plane with four stroke "enough vibration" engine) about two month (jan 2005-mar 2005) at -15..+6C ambient temperature. After power on mosfet is ON, I am use WDT (watchdog timer) to prevent hang-up. To power-off need hold button down about 1 sec. To power on enough short touch of button.
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Old Mar 14, 2005, 07:00 AM
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Manila, Philippines
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Romych: You might use PIC output pin to power a reference Voltage. this will further lower the Turn-OFF current Drain, but this will need extra I/O pin.....you might sacrifice one of those use by LED indicator...I am not sure how your LED indicate voltage, Is it just simple On and Off, or you might use a Modulated LED light....you might use a different Blink Rate to show the Voltage Level.....I guess this can be implemented on your future project.

Keep us posted on your future project.
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Old Mar 14, 2005, 09:22 AM
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Very clever way of multiplexing 4 LEDs on 3 I/O pins.

Adam
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Old Mar 15, 2005, 12:45 AM
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Smolensk, Russian Federation
Joined Aug 2004
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More clever - six LEDs
From microchip Tips&Tricks document
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Old Mar 15, 2005, 08:46 AM
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Very nice. I had to look at it for a minute to figure out how it would work. I am currently using Atmels and will have to try this. Although the Atmels can't source as much current so it may not work as well.

Adam
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Old Mar 16, 2005, 05:43 AM
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Smolensk, Russian Federation
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This schematic utilise ability of I/O pins going to tri-state. About current - for home enoug some milliamps (about 5) for enough brightnes of LED, under sunligh it is not enough

I am have deal with ATTiny 15L it can handle up to 40mA per IO pin (by datasheet, not tested by me).
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Old Mar 16, 2005, 06:59 AM
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Canada
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Nice circuit.. and I all most understand what is going on... I think... Is U1, the 3.0 volt linear regulator shown incorrectly on the schematic?
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Old Mar 16, 2005, 10:17 PM
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Manila, Philippines
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Yes, I guess Romych, did not notice it too.

Romych: Here my another suggestion, which you might add to your future project. I wish you could add an Integrated Timer. this will allow you to monitor the Total time used since the last Reset....you can use a CODED PUSH Sequence to go to different mode

Press for 1 SEC will turn the unit off.
Press for 2 SEC will output the Total Integrated TIME....Output Total Time by Blinking the LED in group of 3, for 3 DIGIT time, just count the number of Blink.
Press for 5 SEC will reset the Integrated timer to zero.

Guys: I use an ANALOG WRIST watch to monitor the total time used...I use TIMEX, just use to silicon diode and 1K resistor in series and connected to receiver supply, use the 2 diode drop to power the wrist watch.

I also use the TIMEX wrist watch to monitor the total discharge time of Battery Discharger.

Ellion
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Old Mar 17, 2005, 01:28 AM
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Smolensk, Russian Federation
Joined Aug 2004
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Quote:
Originally Posted by just_lkn
Nice circuit.. and I all most understand what is going on... I think... Is U1, the 3.0 volt linear regulator shown incorrectly on the schematic?
Yes, I am draw schematic symbols bu myself, and name pins incorrectly. Left will ne IN right - OUT. Thanks for attention.
(it is russian 3.0 v lin. reg. analogue of 78L03 I think)

Quote:
Originally Posted by lazy-b
Press for 1 SEC will turn the unit off.
Press for 2 SEC will output the Total Integrated TIME....Output Total Time by Blinking the LED in group of 3, for 3 DIGIT time, just count the number of Blink.
Press for 5 SEC will reset the Integrated timer to zero.
It is good idea. But I think 2 digits time enough. I am plane to use for indication small LCD display from old Japanies of Chinesse ($1-$2) digital hand clocks. By this display we may show percentage/Voltage/Clock and may be average current. But it require many pins or some decoders chip (binary to seven-segments code). In this case display may be cyclic.
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