Transitter example.

[Sture Hultqvist]

[img]../images/transmit.jpg[/img]


A example of a "spike" transmitter.


Sture

[Bob]

Re: Transitter example.

Sture,


After seeing Jan's comments and your schematic, I was thinking that we could have a variable pulse width..


What do you think of having the driving coil and the transducer act as a resonant circuit so that muliple pulses are sent. (perhaps you do this already)


Then, if we use Jan's idea and add a thrystor to shut down the tank, but control when it is activated, we can adjust the number of pulses sent out.


If we made the pulse width controllable by the PIC, then someone using the sonar could adjust for maximum sensitivity, or maximum resolution.


Also, what does the op amp to the right of this picture do? Is it used to show the pulse with, number of pulses, etc?


-Bob

[Bob]

Re: Transitter example.

Sture,


After seeing Jan's comments and your schematic, I was thinking that we could have a variable pulse width..


What do you think of having the driving coil and the transducer act as a resonant circuit so that muliple pulses are sent. (perhaps you do this already)


Then, if we use Jan's idea and add a thrystor to shut down the tank, but control when it is activated, we can adjust the number of pulses sent out.


If we made the pulse width controllable by the PIC, then someone using the sonar could adjust for maximum sensitivity, or maximum resolution.


Also, what does the op amp to the right of this picture do? Is it used to show the pulse with, number of pulses, etc?


-Bob

[bob]

Re: Transitter example.

Silly me..


For some reason my last message posted twice, and when I came and looked at the schematic again, I realized that The right half is the beginning of the receive circuitry. The diodes clamp the input and prevent overload..


I guess this makes me wonder if we want an underdamped LC circuit on the output, because this will reduce the resolution of the receiver.


Ideally, if we had separate transmit and receive arrays, would we have an inductor connected to the receive array at all? If not, perhaps we should modify Jan's idea to take the coil out of the circuit completely once it has fired...


-Bob

[Jan]

Re: Transitter example.

C22 is charged with 250 V


I expect the 250V DC is generated from 12V by Cascade (?) diode/capacitors. (Like in any TV set)


This charge is discharded through transformer T3 via thyristor (triggered by transistor Q15)


This will give a spike on secondary side of transformator T3 (cannot see coil ratio but expect the transformer steps spike up to 5kV)


This spike is fed to transducer


Without the diodes CR20/CR21 the 5 kV spike will destroy the OPAMP.


To prevent that the diodes are used so the maximum voltage to OPAMP is limited to -0.7V to +0.7V.


The thing I have not yet figured out is the use of diodes CR18 & CR19.


Anyone suggestions ?


Regards, Jan