Convert (invert) a pulse

[firewalker]

I have the following logic:

When a switch is not pressed the output is 24 volts. When the switch is pressed the voltage is 0. It is the output of a motor sending this pulse on every cycle. It sends continuously 24 volts and a 0 pulse when it completes a cycle.

I want to invert this Logic. I want 0 volts and a 24 volts pulse on every cycle of the motor.

I started to design a circuit with a transistor but I am stubbed for the moment…

The circuit should be fast enough to “read� frequencies up to 50 kHz.

[nacho1]

if You want to drive a relay this schematic might help you:
http://www.wam.umd.edu/~toh/ElectroSim/Relay.GIF

if you only want to have an inverted signal, then this are the calcs:

condition to saturate the transistor ic>>ib, do ic>=10 x ib. so:

rc = Vcc-Vce_(sat)
       ---------------------------
                        ic


rb = VCC-Vbe
        ---------
            ib


so choose your Ic, calc rc,
then ib=ic/10
and then calc rb

whis is an example with 5v & 12v for vcc
http://www.mayothi.com/images/transistor3.gif

you shuld take the signal from the colector
I hope it helps
greetings

[ppa88]

Here is a simple proteus simulation to illustrate it.

http://rapidshare.com/files/68256398/invert.rar.html

[pl4tonas]

I suggest to use the transistor circuit proposed by the posts above but with an extra resistor connected between base-emmiter.
This should have a value between 2K2 to 10K (recomment the 2K2 or 3K3 value) and is used to ensure that any voltages near 0v i.e. 0.5 or 1V, would be treated as 0 level.