Help with "Data switch"

[KrisBlueNZ]

Try again; I've just updated that post with a complete diagram.

 

[HellasTechn]

This has worked in the simulation.

What do you think ?

In this circuit i think that when the input (Base of transistor) is 0 then the output (Pin 3 of 555) will not be stable but pulsating (going from high to low and high again) because when the capacitor is discharged then it will be charged again in next cycle and then discharged etc...

???

 

[HellasTechn]

I just saw the schematic.

I will materialise it and field test it tommorow.

Man I dont know how to thank you !!!!!!!!!!!


Such help and fast response that suits my needs i have never seen before.

Needless to say how much monay you saved me !

 

[HellasTechn]

The voltage divider (R1 and R2) and C1 improve the circuit's immunity to noise on the RS-232 data line. C1's value is chosen to suit data rates up to 9600 bps. If the GPS receivers use a data rate higher than that, C1 must be reduced accordingly. D1 protects Q1 from possibly damaging negative base voltage.
.

So with baud rate 4.800 i should be fine useing theese values.

 

[HellasTechn]

The circuit you gave me works just fine.

Even better than i hoped because when i was examining the output of the GPS i found out that it has a 1PPS (one pulse per second) syncronizing output that was ment to be hooked up to radio receivers that reqiure timing. So not only the switch works when GPS-1 looses power but also it works if GPS-1 looses contact with the sattelites.

Thank you so much KrisBlueNZ !!!!

 

[KrisBlueNZ]

Yes, 4800 bps is fine.
You're welcome; no problem.
Good luck!

 

[HellasTechn]

Yes, 4800 bps is fine.
You're welcome; no problem.
Good luck!

My dear friend. You have no idea how helpfull this circuit has been proven to me !

From inside my hart i give you my best whishes for your help !

 

[KrisBlueNZ]

Actually, reading back through this thread, it looks like you had already found most of the design by yourself! But you're welcome anyway