[SOLVED] transmitting pwm signal over a distance of 10-15 feet

[vijayjadhav.595]

Hi,
I am using a ATMEGA-32U4 to generate a pwm signal(square wave) with varying frequency(30-25 Khz) with a constant pulse width of 120nS. The signal is generated but i am having issues in transmitting the signal over a coaxial cable of length 15 feet. At this point the signal recieved on the other end of the cable appears to be distorted.I guess, the sourcing controller is not able to drive the signal over such a long cable and hence distorted. so I plan to use a line driver.
my question is whether my line of thinking the correct one and if it is can any one suggest me the correct line driver IC to use considering the freq and pulse width of my signal.

cheers..
vijay.

 

[crutschow]

You could use a 74128 50 ohm line driver. Not that the output goes from 0.4V to 2.4V minimum. You will need a 50 ohm load at the other end connected to +5V and a TTL circuit or comparator to sense the signal at the receiver end.

 

[dick_freebird]

If your cable is of known impedance then maybe you
just want to line-match through a resistor divider,
and use a receiver with suitable gain at the far end.
Which might just be a Schmitt input and centering bias.

CAT-5 cable and RS-422 (like 26LS31, you can drive
that with 2.5 or 3.3V logic as well as 5V; use 26C32
at the tail end with whatever scaling divider the
destination input wants) would work, cheaply. The
differential signal ought to more than make up any
noise margin you lose from not being coax, and you
can ground the CAT-5 foil too.

 

[FvM]

RS-422 would also be my first suggestion and can work up to 10 or 20 MHz, depending on the driver and receiver type. A good thing is the about +/- 7V common mode range of RS-422 receivers which make it work even in a rather "noisy" enviroment.

If high noise isn't an issue, a strong CMOS gate (or several gates in parallel) with source side termination (50 ohm series resistor) and a high impedance receiver (a CMOS input) will work over regular 50 ohm coaxial cable on considerably longer distance, e.g. 100 feet/30 m.

 

[vijayjadhav.595]

Hi,
Thank you all for the suggestions. They Really helped. I used a 7HCT245 and it worked fine