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Subject: changing dc polarity

Date: 03/07/03 at 12:54 PM
Posted by: janet
E-mail: janet_smith2000@yahoo.com
Message Posted:

CASE 1:

i wish to use a digital control signal (1 or 0) to control a 9.6 V DC motor.
The direction of DC motor depends on voltage polarity.
when the signal is '1' (5v), the motor will move in one direction, and when the signal is '0' (0v),
the motor will move in opposite direction. in another word, how to change the polarity of output voltage?

CASE 2:

I am using a 27 MHz Tx/Rx. When i pressed forward, the output is '+ -'; when i pressed backward, the output is '- +'.
i wish to connect directly to the dc motor. However, the output of the Rx is just about 6V. I wish to 'step-up' the output to 9.6V, how to do this?

CASE 3:
in order to have 8 ways movement (up, down, left, right, up, down, 2 spare), i use two pair of Tx/Rx. One is 27MHz, another one is 49MHz.
However, when i pressed the button of 49MHz Tx, both corresponding output (i tested by using LEDs) of 27MHz and 49MHz Receiver will light up.
However, when i pressed the button of 27MHz Tx, only the output of 27MHz will light up.

The same case when i tested with 27MHz and 33 MHz, and 33 MHz and 49 MHz, the Tx/Rx with lower frequency will be affected.

Thus, i wish to disable the 27 MHz Rx when i sending signal using 49 MHz. I was thinking to use a Inverter and an AND gate to realize it.
however, this is not digital system, the output of Rx may have negative voltage (different polarity).
so, what's the better solution?


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