Dual DC voltage output for different time intervals

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#1 21661787 17 Apr 2012 09:02

Paritosh Sinha Paritosh Sinha

Anonymous

Post #1
21661787 17 Apr 2012 09:02

i have to generate two different DC voltage levels in two different time intervals like
5V for 60 seconds
and
1.4V for 90 seconds

what is the simplest way to achieve this. I need the circuit for the MQ-7 carbon monoxide gas sensor.

thank you
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#2 21661788 17 Apr 2012 09:21

Stephen Shaffer Stephen Shaffer

Anonymous

Post #2
21661788 17 Apr 2012 09:21

The two voltages you need, are they to the same pin? If not, then use a resistor voltage divider to achieve the 1.4v from a standard 5v output pin.
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#3 21661789 17 Apr 2012 13:58

Steve Lawson Steve Lawson

Anonymous

Post #3
21661789 17 Apr 2012 13:58

depends on how precise the timing needs to be. If not precise, you could get away with a simple 555 timer circuit. Otherwise, perhaps a CD4060 with taps run to a voltage divider (and emitter-follower transistor buffer if current amplification is needed, or the CD 4060 could, perhaps control programming resistors on an LM317). Beyond, that, I would say use a microcontroller.
#4 21661790 18 Apr 2012 05:31

Paritosh Sinha Paritosh Sinha

Anonymous

Post #4
21661790 18 Apr 2012 05:31

the two DC voltages should be available to the same pin
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#5 21661791 18 Apr 2012 05:33

Paritosh Sinha Paritosh Sinha

Anonymous

Post #5
21661791 18 Apr 2012 05:33

we can have some relaxation in the area of precision..... but we do not intend to use a microcontroller for this purpose ........ can i have an elaboration on the 555 timer circuit
#6 21661792 18 Apr 2012 16:51

Steve Lawson Steve Lawson

Anonymous

Post #6
21661792 18 Apr 2012 16:51

You do the math...
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#7 21661793 18 Apr 2012 16:54

Steve Lawson Steve Lawson

Anonymous

Post #7
21661793 18 Apr 2012 16:54

Here's a better one -- much simpler!
#8 21661794 18 Apr 2012 17:01

Steve Lawson Steve Lawson

Anonymous

Post #8
21661794 18 Apr 2012 17:01

And, actually, the output will probably need to be inverted, so try this...
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Dual DC voltage output for different time intervals

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